construction exe 09 august sr i 2010 module stringing
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FOR INTERNAL CIRCULATION ONLY
user’s manual of
construction(part one)
Transmission LinesVolume-5Stringing
Construction ManagementPower Grid Corporation of India Limited
(A Government of India Enterprise)
DOCUMENT CODE NO. : CM/TL/STRINGING/ 96 NOV. 1996
Vol.5 : Page #
CHAIRMAN&
MANAGING DIRECTOR’S MESSAGE
It gives me immense pleasure to learn that Construction Management Deptt. has come
out with further 3 volumes of User’s Manual of Construction of transmission line
(Stringing) & Sub-station (Mechanical) and Electrical auxiliary packages).
For quite sometime a need was also being felt in the organization to develop and
prepare standard procedures, norms and guidelines for execution of various
construction activities as the different regions were following different practices. It is
with this background the construction management department was conceived at
Corporate Centre and entrusted with the task of developing and providing such user’s
manuals of construction and to bring in uniformity. These manuals shall serve as a
useful reference to our field engineers and site managers to accomplish a task in given
time, cost & quality.
I would like to congratulate Construction Management team for its sincere efforts in
preparation of these manuals wherein the main focus has been to bring together all the
theoretical and practical knowledge acquired during the years in the domain of
construction of overhead transmission lines and s/stn. More such user’s manuals
covering the other related fields in the lines/sub-station construction should be
prepared for the benefit of the ultimate users at our remote sites as well as for the
younger generation inducted in the POWERGRID.
(R.P. SINGH)
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CONTENTS
CHAPTER 1
CONDUCTOR AND EARTHWIRE SELECTION
CONDUCTOR CREEP AND SAG-TENSION CALCULATION
PAGE NO.
1.1 SELECTION OF CONDUCTOR 1
1.1.1 POSSIBLE TYPES OF CONDUCTORS 1
1.1.2 SUB-CONDUCTOR SPACING 4
1.1.3 ELECTRICAL CONSIDERATION 7
1.1.4 STRUCTURAL CONSIDERATION 9
1.2 SELECTION OF EARTHWIRE 10
1.2.1 FUNCTION OF GROUND WIRE 10
1.2.2 HOW GROUND WIRE PROTECTS 12
1.2.3 SHIELDING ANGLE AND MID SPAN CLEARANCE 13
1.3 ORIGIN OF CONDUCTOR CREEP 14
1.3.1 PRIMARY AND SECONDARY CREEP 14
1.3.2 EFFECT OF CREEP 15
1.3.3 CREEP ALLOWANCE 16
1.3.4 COMPARISON OF METHODS 17
1.3.5 PRECAUTIONS DURING STRINGING 17
1.4 SAG TENSION CALCULATION 18
1.4.1 CATENARY AND PARABOLIC FORMULAE 18
1.4.2 COORDINATION OF SAGS 21
1.4.3 STRINGING CHARTS 22
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CHAPTER 2
DEFINITIONS AND TERMINOLOGY
PAGE NO
ACSR CONDUCTOR 24
BLOCK 25
BULL WHEEL 27
CLIPPING IN 29
CONDUCTOR CAR 30
CONDUCTOR GRIP 33
RUNNING GROUND 35
TRAVELLER GROUND 36
COMPRESSION JOINT 37
PROTECTOR JOINT 38
PILOT WIRE 40
BULL WHEEL PULLER 43
REEL STAND 46
RUNNING BOARD 47
BULL WHEEL TENSIONER 53
TRAVELER 54
UPLIFT ROLLER 55
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CHAPTER 3
STRINGING METHODS AND GENERAL ASPECTS
3.1 METHODS OF STRINGING 57
3.1.1 MANUAL METHOD 57
3.1.2 TENSION METHOD 58
3.2 GROUNDING DURING STRINGING 59
3.2.1 INTRODUCTION 59
3.2.2 SOURCE OF HAZARDS 61
3.2.3 GROUNDING PROCEDURE 61
3.3 COMMUNICATIONS 62
3.4 SPECIAL REQUIREMENTS FOR 63
MOBILE EQUIPMENT
3.4.1 DRUM OR REEL STAND 63
3.4.2 TENSIONER BULLWHEEL 64
CHARACTERISTICS
3.4.3 PULLER AND TENSIONER OPERATING 66
CHARACTERISTICS.
3.5 TRAVELERS 68
CHAPTER 4
STRINGING PROCEDURE
4.1 STEPS OF STRINGING 78
4.2 STRINGING OF EARTHWIRE 78
4.2.1 PAYING OUT OF EARTHWIRE 78
4.2.2 JOINT OF EARTHWIRE 79
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4.2.3 SAGGING AND FINAL TENSIONING 81
4.2.4 CLIPPING 83
4.2.5 FIXING OF HARDWARE 84
4.3 STRINGING OF CONDUCTOR 85
4.3.1 GUYING OF TOWERS 85
4.3.2 INSULATOR HOISTING 86
4.3.3 PAYING OUT OF PILOT WIRE 90
4.3.4 POSITION OF TENSIONER AND PULLER 90
4.3.5 PAYING OUT OF CONDUCTOR 92
4.3.6 REPAIRING OF CONDUCTOR 96
4.3.7 JOINTING OF CONDUCTOR 97
4.3.8 ROUGH SAGGING OF CONDUCTOR 100
4.3.9 FINAL SAGGING OF CONDUCTOR 101
4.3.10 REGULATION 104
4.3.11 CLIPPING OF CONDUCTOR 105
4.3.12 FIXING OF LINE SPACER 106
4.3.13 INSTALLATION OF DAMPERS 108
4.3.14 JUMPERING 108
4.3.15 PAYING OUT THROUGH ANGLE TOWERS 110
4.3.16 TRANSPOSITION ARRANGEMENT 111
4.4 STRINGING OVER RIVER CROSSING 113
4.5 STRINGING OVER POWER LINE CROSSING 116
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CHAPTER 5
GUIDE LINES
GL - 1 PRE STRINGING CHECKS 119
GL - 2 PAYING OUT OF EARTHWIRE 125
GL - 3 PAYING OUT OF CONDUCTOR 128
GL - 4 FINAL TENSIONING OF EARTHWIRE AND CONDUCTOR 135
GL - 5 CLIPPING AND FIXING OF EARTHWIRE ACCESSORIES 140
GL - 6 CLIPPING AND FIXING OF CONDUCTOR ACCESSORIES 143
ANNEXURE S/1 REQUIREMENT OF TOOLS AND PLANTS
FOR STRINGING 149
ANNEXURE S/2 REQUIREMENT OF MANPOWER
FOR STRINGING 153
CHAPTER 6
CHECK FORMAT 154
BIBLIOGRAPHY 170
RESUMES
(v)
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______________________________________________________________________
CHAPTER ONE
______________________________________________________________________
CONDUCTOR AND EARTHWIRE SELECTION
CONDUCTOR CREEP AND SAG-TENSION CALCULATION
Back to Contents Page
1.1 Selection of Conductor
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1.1.1 Possible Types of Conductors :
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(i) Up to 220 kv lines, the basic criteria for selecting
the size of conductor is its continuous and short-term
current carrying capacity both under normal and short
circuit conditions. However, for EHV lines this
criteria does no longer hold good, as corona and its
effects come into picture which are function of line
voltage. For 400 kV lines, therefore, size of
conductor is determined not only from current carrying
capacity considerations but also from corona and radio
interference considerations. The experience has
established that the size of conductor which gives
satisfactory corona and RI performance would have
adequate current carrying capacity also. The size of
conductor so determined would normally be larger than
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Chapter-1
Conductor & Earthwire Selection Conductor
Creep & Sag-Tension Calculation
that selected from considerations of power
transmission capability.
(ii) One of the methods to achieve this would be to have a
single conductor with large diameter. However, due to
heavier weight of such a conductor, its manufacture,
handling, transportation and stringing would be
difficult and expensive. Use of single conductor was,
therefore, not considered for 400 kv lines.
(iii) Another method of increasing the size of conductor,
which some utilities in America have tried, is to use
expanded conductor, in which minimum amount of
aluminum necessary to carry the power is retained,
and inert low cost filler material is stranded around
the aluminum portion to increase the overall diameter
of the conductor. However, its use has not found
popular support even in America, due to manufacturing
and other problems. This conductor was also,
therefore, not considered for 400 kv lines.
(iv) The only other alternative was to use bundle
conductors consisting of 2,3 or 4 small size sub-
conductors to obtain required effective overall
diameter of the conductor. For EHV lines, this is the
most technically suitable, economical and commonly
adopted method to transmit bulk power over long
distance. The bundling reduces the inductive reactance
loading and improves the stability of the line. The
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voltage gradient is reduced to acceptable limit,
thereby improving the corona and radio interference
performance. Studies indicated that for the 400 kv
lines 2 or 3 sub-conductors in each bundle would be
sufficient.
Table 1.1 gives the number, size and other physical
properties of various conductors.
Table 1.1: Number, Size and Physical properties of Conductors ------------------------------------------------------------------------------------------------ Code No. of Sub- Stranding Overall Unit wei- U.T.S. Approximate Name conductors (mm) dia. ght (kg/m) (kg) current carry- (mm) ing capacity 40°C ambient temperature------------------------------------------------------------------------------------------------Goat 3 30/7/3.71 25.97 1.492 13780 680 Sheep 3 30/7/3.99 27.93 1.726 15910 745 Deer 2 & 3 30/7/4.27 29.89 1.977 18230 806 Zebra 2 & 3 54/7/3.18 28.62 1.625 13316 795 Elk 2 & 3 30/7/4.50 31.50 2.196 20240 860 Camel 2 54/7/3.35 30.15 1.804 14750 - Moose 2 54/7/3.53 31.77 2.002 16450 900
Bersimis 2 & 4 42/4.57 35.10 2.181 15715 -
7/2.54
AAAC 2 61/3.55 31.95 1.666 16307 - -----------------------------------------------------------------------------------
1.1.2 Sub-conductor Spacing
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(i) After having selected the conductor with twin bundle
arrangement, the sub-conductor spacing had to be
decided. Sub-conductor spacing influences the surge
impedance loading (SIL) of the line, corona and radio
interference performance, line losses and the weight
of towers. The cost of series and shunt compensation,
due to change in the reactance of the line, is also
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affected to some extent. A phenomenon known as sub-
span oscillation is also related to sub-conductor
spacing. All the above factors when combined affect
the cost per MW capability of line.
(ii) From the experience and practices adopted by
different countries for 400/500 kv lines, it was found
that the optimum sub-conductor spacing would vary
between 30 to 45 cm. However, a wider range of sub-
conductors spacing form 20 to 50 cm was considered.
(iii) Figure 1.1 shows the surge impedance loading of twin
'Moose' conductor bundle with different sub-conductor
spacings varying from 20 to 50 cm, and inter phase
spacing from 10 to 16 m. With increased interphase
spacing and reduced bundle spacing, the transmission
capability is reduced due to increased inductive
reactance and reduced capacitive reactance of the
line. Accordingly, the amount of series and shunt
compensation of line is also influenced.
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(iv) The tower weights are influenced with the change in
the sub-conductor spacing due to following reasons:
(a) With given configuration of towers, and specified
angle of shield, the cross-arm length increases with
the increase in sub-conductor spacing. This involves
an increase in the height and hence the weight of
towers.
(b) With increase in cross-arm length, the torsional load
increases under broken wire conditions, resulting in
increase in the weight of bracings.
(v) The I²R and corona losses also get affected with
change in sub-conductor spacing due to change in SIL
and surface gradient.
(vi) Apart from the above, sub-conductor oscillations have
also been found to be related to sub-conductor
spacing. These are low frequency and high amplitude
oscillations which may be so severe under certain wind
conditions as to cause clashing of sub-conductors in
the mid sub-span, and thus resulting in damages to the
suspension fittings, spacers and subsequently to
conductors. Through extensive research and
experience, it has been found that the amplitude of
sub-conductor oscillations is reduced as the sub-
conductor spacing is increased, and these can be
controlled considerably by keeping a sub-conductor
spacing-to-diameter ratio more than 14-15. The 400 KV
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lines constructed by CEGB in U.K. with 300 mm sub-
conductor spacing with twin "Zebra' bundle have
experienced trouble due to such sub-conductor
oscillations. Subsequently, they are reported to
have increased the sub-conductors spacing to 500mm
(20 in.) increasing the spacing-to-diameter ratio
from 10.4 to over 17.
(vii) For twin 'Moose' bundle, the optimum sub-conductor
spacing was lying between 45 and 50 cm as shown in
Figure 1.2. The decision, however, went in favour of
45 cm sub-conductor spacing in view of the following
reasons.
(a) For most of the European and American utilities the
sub-conductor spacing for 400/500 kv lines was
varying from 30 cm to 45.7 cm, and a spacing of 45
cm was most commonly adopted (Details in Table 1.2).
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(b) As the spacing of 45 cm was most common, the design Vol.5 : Page #
and performance of spacers and hardwares at this
spacing were well-known.
(c) The corona and radio interference performance was
found satisfactory.
(d) The sub-conductor spacing-to-diameter ratio is more
than 14.
(viii) The horizontal configuration of bundling was
selected, as it is the most common arrangement for
twin bundle conductors, although in some cases for
lower voltages upto 345 Kv, vertical bundling has also
been adopted.
1.1.3 Electrical Considerations :
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(i) Current Carrying Capacity
The conductor selected for EHV lines should be
capable of carrying currents under normal as well as
peak loads, without getting overheated. The stability
of the line should not be disturbed, both under
steady state and transient conditions. The surge
impedance loading, in which reactive power consumed by
the line reactance equals the reactive power generated
by the line capacitance, has been calculated as 505
MW (in Figure 1.1) for twin bundle, 'Moose' conductor
with 45 cm sub-conductor spacing, which meets the
normal load requirements of our system. By providing
necessary compensation for reactive power, the
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emergency peak load can also be transmitted without
affecting the stability of the line.
The excessive temperature rise over the ambient
temperature under full load conditions, some time,
may impose a limit of the MVA which can be
transmitted. However, in case of 'Moose' ACSR, the
maximum current carrying capacity for a temperature
rise of 35°C on an ambient temperature of 40°C is
about 900 amps. This provides a limit of power
transmission of 1250 MW from thermal considerations,
which is much more than normal and peak load
requirement of our line.
(ii) Corona and Radio-Interference
When the electric field on the surface of the
conductor exceeds the disruptive field of surrounding
air, corona effect takes place with discharges
emitting from the periphery of the conductor. This
phenomenon produces additional loss of power, radio
disturbance and audible noise. The surface gradient
is proportional roughly to the under root of line
voltage and inversely proportional to diameter of
conductor for a fixed line voltage. It is, therefore,
necessary to limit the surface gradient by increasing
the diameter of conductor. The bundling of conductor
is the most suitable choice, as already stated in
para.1.1.1
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TABLE 1.2: Particulars of EHV lines of some foreign countries
----------------------------------------------------------------Items Italy France Finland Sweden U.S.A. U.S.A U.K.
----------------------------------------------------------------Line Voltage 380 kv 380 kv 400 kv 380 kv 500 kv 500 kv 400 kv
Year of cons-truction 1963 1963 1960 1965 1965 1966 1965
Nature of Conductor ACSR ACSR ACSR ACSR AL-alloy ACSR ACSR
No. of sub-condu ctorsper phase 2 2 2 2 2 2 2
Al/st area of conductor 7.9 4.87 7.9 7.7 - 12.5 7.71
Sub-conductorctor spac- 40 40 45 45 45.7 45.7 30.4 ing(cm)
----------------------------------------------------------------
1.1.4 Structural Considerations :
Back to Contents Page
The electrical advantages of bundle conductors are
counteracted to a great extent by the structural
disadvantages. The mechanical loadings on the
supporting structures increase considerably with
bundle conductors which result in heavier towers and
foundations. The bundling of conductors also
necessitates complicated hardwares and accessories,
thereby increasing the cost of line. However, we have
to reach to the compromise for optimum choice of
conductor.
1.2 Selection of Ground wire
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1.2.1 Function of Ground wire :
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(i) As is well known, groundwires are the conductors
arranged above the phase conductors and grounded at
every tower. They mainly afford the protection
against direct strokes and distributing the current
in two or more paths, thus reducing the voltage drop.
Another function of the groundwire, of a minor
nature, is to reduce voltage induced on the
conductors from nearby strokes. In case of Extra High
Voltages, the over voltages due to direct or induced
lightning strokes are not the governing factors and
the insulation selection is based on switching
overvoltage, the ground wire still protects the line
and equipment from damage due to direct or induced
lightning strokes by shielding. It also reduces strain
across the insulator string, in case of stroke, due
to its inherent coupling with the conductor. To
perform this, it must meet the following requirements:
(a) It must be able to carry the maximum lightning
current, without undue overheating.
(b) It must be strong mechanically.
(c) It must be high enough to afford protection to all
the line conductors at mid-span to prevent a side
flash to a line conductor during the interval
required for reflections from the towers to return to
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mid-span and relieve the voltage stress there.
(d) Tower footing resistance should be low.
Size of Earthwire for EHV lines : G.S. 7/3.66mm,
overall dia. 10.98mm, wt. 0.583 Kg/m, UTS 6980 Kgs.
(ii) In addition groundwires exercise a number of
subsidiary effects, some of which are:
(a) Telephone and radio interference.
(b) Corona.
(c) Relaying possibilities.
(d) Zero sequence impedance of the line.
(e) Attenuation of travelling waves.
(f) Reduction in surge impedance.
1.2.2. How Groundwire Protects:
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(i) In case of lightning stroke on a transmission line,
the line can be struck either at tower point or at mid
span. When the ground wire is struck at mid - span
the current divides in two parts and flows towards
both towers and at the tower the current again
divides into two parts, one going to the tower and the
other to outgoing portion of the ground wire. If
the tower is struck and there is one overhead ground
wire, the current divides into three parts, one in the
tower and two in the groundwire on either side of the
tower. The strokes on the tower and within a quarter
span on either side of it, are assumed to be on
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tower and treated as such. The strokes on the
middle half span are supposed to be on the mid-span
and dealt with as such.
(ii) In case of stroke, the lightning surge voltage
travels from the point struck to the ground
through tower. From the tower footing the wave is
reflected, and this reflected wave, though reduced in
magnitude depending on footing resistance, cancels
out to a great extent, the incident wave. The
lightning surge, therefore, remains on the point
struck, at tower top or mid-span, for a time taken by
the incident surge to reach the tower footing and
for the reflected surge to reach the point struck.
During this time the point struck will be stressed
by the voltage of surge wave and should not
flashover, i.e., there should be no insulation
flashover for tower strokes and no mid span flash
over for mid span strokes. The insulation level
of a line is, therefore, decided on this basis (for
EHV lines, insulation level is decided based on
switching surges). Similarly, the mid-span
clearance is also kept such that no flashover occurs
during the time, the surge voltage is impressed on
the mid-span.
1.2.3 Shielding Angle and Mid-Span Clearance:
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(i) Shielding Angle
The shielding angle afforded by a groundwire is
defined as the angle between a vertical line through
the groundwire and the slanting line connecting the
earthwire and conductors (outer conductors in case of
bundles). The protective zone of groundwire is the
cone with the groundwire at its apex and the shield
angle as its slanting angle. The earthwire is
supposed to protect all the conductors within this
zone from direct strokes. In actual practice,
however, the probability of flashover is less with
lower shield angle and high with higher shield angle.
On the other hand, lower the shield angle, higher is
the tower, and hence higher the cost of line. So a
compromise has to be reached between the line cost and
protection afforded.
(ii) Mid - span Clearance:
In case of stroke on mid-span, very high voltage is
impressed on the groundwire. The voltage remains on
the groundwire, till such time the reflection of the
wave returns. The voltage on the groundwire may,
therefore, cause flashover from groundwire to
conductor or what is known as "back flashover", if
sufficient clearance is not provided between the
earthwire and conductor at mid-span. This clearance
is, therefore, kept such that the voltage surge may
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not cause flashover during the time it is impressed
on the earthwire.
1.3 Origin of Conductor Creep
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1.3.1 Creep is time-dependent strain occurring under stress.
A bare overhead line conductor will suffer a permanent
increase in sag from non-elastic stretch caused by
following:
(a) Short time loading such as from wind and/or ice loads,
or after being subjected to tension during conductor
installation. In these cases the difference of
initial and final modulus of elasticity is involved.
(b) Long time loading at any tension and temperature
level, which is known as 'long-term tensile creep' or,
simply as 'Creep'.
(c) The first stage [para-(a)] is generally known as
'Primary Creep' in which the conductor initially
creeps quite quickly with a rapid decrease in creep
rate. This mainly represents a considerable amount of
strand tightening and settlement, adjustment of load
between layers, stress shifting between components of
a composite (e.g., ACSR) conductor, and partial
metallurgical creep.
(d) The second stage [para (b)] is known as 'Secondary
Creep' in which the creep is more stable and is mainly
metallurgical. In this case the creep and the decrease
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in creep rate are both very slow.
1.3.2 Effect of Creep
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As mentioned above, creep results in permanent
increase in conductor sag and, if not properly
controlled, can cause irregular bundle sags, smaller
electrical clearance to ground and to earthed metal
parts; and may require re-sagging operation at a later
stage. The amount of this creep during the estimated
or considered line life will depend upon everyday
stress and everyday temperature operating.
1.3.3 Creep Allowance :
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There are two methods of creep adjustment as
mentioned below. Both are in regular use and are
equally popular. It is most convenient to express
creep or permanent sag increase in terms of a
temperature-increase above the ambient.
(i) Overtensioning :
In this first method, allowance for creep during
sagging is made either by including creep correction
in the stringing charts thereby producing 'Erection'
or Initial Stringing Charts, or by reading the sag
from 'final or design' Stringing Charts (hereafter
referred as design stringing charts) at ambient
temperature minus the established temperature
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correction for creep.
(ii) Allowance in Design :
In the second methods, sagging is done to design
stringing charts and the permanent sag increase is
allowed for in the tower design by providing
equivalent extra clearance from the bottom cross-arm.
1.3.4 Comparison of the Two Methods :
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The first method will initially result in some tower
overloading though it also results in savings from
reduced tower height.
The second method finally results in lower tower
loadings with age, which means the line life and
stability can be expected to be more than that
achieved with the first method due to reduced tension
and vibration effects. At the same time, there is no
chance of design tensions being exceeded. Further,
lighter and cheaper tensioning equipment will be
required.
The first method normally requires erection stringing
charts, whereas the second method requires furnishing
of only design stringing charts which have to be
furnished in either case.
1.3.5 Precautions during Stringing
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Prestressing as per stringing charts effectively
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stabilizes the conductor from creep during its
installation. It is important that all the conductors
in a sagging section are handled uniformly as regards
tension and time during stringing, prestressing and
sagging. The subconductors of a phase should be of
the same make out of the same process of manufacture
(e.g. wire drawn from either hot-rolled rod, or
extruded and drawn rod.)
1.4 Sag-Tension Calculations
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1.4.1 A proper evaluation of sags and tensions is necessary
at the design stage for fixing up the ruling span and
structural requirements of line supports. During
erection of the overhead lines, the sags and tensions
to be allowed for various spans under the ambient
conditions will also have to be properly evaluated,
so that the lines may give long and trouble-free
service. Various methods, analytical and graphical
have been devised to determine the sag and tensions.
If the flexible conductor, whose weight is distributed
uniformly along its length, is suspended between two
rigid supports at the same level and is in
equilibrium, its contour lies along a curve which
conforms quite closely to a catenary the longer
the span, the greater the degree of conformity.
The transmission line conductor is usually subjected
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to the following external forces:
(i) a horizontal force due to wind pressure,
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(ii) a vertical force due to the dead weight of the
conductor, and
(iii) A vertical force due to the deposit of ice on the
conductor (in areas subject to snow fall)
If w is the weight of conductor per metre length
(including the weight of ice deposit, if any) and p
the horizontal force due to the wind pressure acting
on the ice-coated conductor per meter length, the
resultant force q on the conductor per unit length is
q = ( w² + p²)
and the catenary which lies in the plane of the
resultant force is inclined to the vertical plane at
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an angle which is given by the equation.
p Tan = --- w
Figure 1.3 represents a span of transmission line
conductor strung between two points of supports A and
B at the same elevation. The length, sag and tension
of the conductor are given by the following catenary
formulae:
2H aqL = ---- Sin h ----
q 2H
H + aq + b = ---- ¦ Cos h ---- -1¦ q ¦ 2H ¦ + +
T H aq ---- = ---- Cos h ---- q q 2H
T H ---- = b + ---- q q
where,
a = span AB,
b = sag of the conductor at its lowest point
with reference to the points of support.
L = length of the conductor in span.
T = tension at either point of support, and
H = horizontal tension at the lowest point O.
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For spans of the order of 300 meters and less, the above
characteristics of the conductor are given with
sufficient degree of accuracy by the following simpler
parabolic formulae, which can be derived by expanding
the hyperbolic functions in the above equations in the
forms of a series and neglecting all terms except the
first two:
a3q² L = a + ---- 24H²
a²q b = ---- 8H
T a²q H ---- = ---- + ---- q 8H q
The above parabolic formulae are generally used in
sag and tension calculations except in the case of
very long spans.
1.4.2 Co-ordination of Sags
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The spacing required between the ground wires and
conductors at midspan to ensure that a lightning
stroke which hits the ground wire does not flashover
to the conductor, is referred to as the midspan
spacing. As a rule, from the lightning protection
point of view, the ground wire is strung with a
lesser sag (by about 10-15 percent) than the
conductor so as to give a midspan separation greater
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than at the supports.
Certain steps are involved in determining the midspan
spacing which, while satisfying the requirements of
factors of safety under the worst condition and the
everyday condition, results also in economical tower
configuration.
1.4.3 Stringing Charts
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The initial sag-tension charts give sags and tensions
for new ACSR before it has been subjected to the
assumed maximum loading stresses. The final charts
give sags and tension after the conductors have been
stressed due to the assumed maximum loading
conditions, when sagged initially in accordance with
the initial charts.
The initial charts are used for determining sags for
the use of stringing the conductors in a particular
ruling span, determined for a section of line between
two dead-end points. The final charts are used for
determining clearances. They are also used for
stringing when the conductors are prestressed before
or during erection at tensions which will subject them
to the same stress they would receive with the assumed
maximum loading conditions.
An example of using the sag-tension chart for the
'Moose' ACSR used on a typical 400 KV single circuit
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line is given below.
The initial sag-tension chart for the conductor is
given in Figure 1.4.
Corresponding to the stringing temperature of 32°C (on
the right corner) and a ruling span of 350 meters on
the X-axis, the tension is 4,010 kg. as read off on
the ordinate. Corresponding to this stringing tension
and the actual span of 400 meters (on the top left
hand corner of the chart), the sag is read as 10
meters on the X-axis.
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Chapter-2
Definitions & Terminology
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CHAPTER TWO
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DEFINITIONS AND TERMINOLOGY
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Terminology for equipment and procedures associated with the
installation of overhead transmission line conductors varies
widely throughout the utility industry. Therefore, definitions
and terminology have been included to provide a correlation
between the terminology used in this manual and industry
synonyms. Note that the synonyms are terms that are commonly
used, although many are not necessarily good usage and should
not be taken as equivalents to the manual terminology.
Definitions & Terminology for Conductor Stringing Equipment.
AAAC. Concentric-lay-stranded all aluminum alloy conductor.
AAC. Concentric-lay-stranded all aluminum conductor.
Aluminum Conductor, Steel Reinforced (ACSR)
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A composite conductor made up of a combination of aluminum and
coated steel wires. In the usual construction, the aluminum
wires surround the steel.
Aluminum Alloy Conductor, Steel Reinforced (AACSR)
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A composite conductor made up of a combination of aluminum alloy
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and coated steel wires. In the usual construction, the aluminum
wires surround the steel.
Aluminum Conductor, Aluminum Alloy Reinforced (ACAR)
A composite conductor made up of a combination of aluminum and
aluminum alloy wires. In the usual construction, the aluminum
wires surround the aluminum alloy.
Anchor
A device that serves as a reliable support to hold an object
firmly in place. The general term "anchor" is normally
associated with cone, plate, screw, or concrete anchors. The
terms snub, deadman, and anchor log are usually associated with
pole stubs or logs set or buried in the ground to serve as
temporary anchors. The latter are often used at pull and
tension sites. Syn: anchor log, deadman, snub.
Block
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A device designed with one or more single sheaves, a wood or
metal shell, and an attachment hook or shackle. When rope is
reeved through two of these devices, the assembly is commonly
referred to as a block and tackle. A set of fours refers to a
block and tackle arrangement utilizing two 4 in double sheave
blocks to obtain four load-bearing lines. Similarly, a set of
fives or a set of sixes refers to the same number of load-
bearing lines obtained using two 5 in or two 6 in double sheave
blocks, respectively. Syn: Set of fours, set of fives, set of
sixes. (Fig. 2.1, 2.2 & 2.14)
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Hold-down block
A device designed with one or more single groove sheaves to be
placed on the conductor and used as a means of holding it down.
This device functions essentially as a traveller used in an
inverted position. It is normally used in midspan to control
conductor uplift caused by stringing tensions, or at splicing
locations to control the conductor as it is allowed to rise
after splicing is completed. Syn:block, splice release; roller,
hold-down; traveler, hold-down.
Snatch Block
A device normally designed with a single sheave, wood or metal
shell, and hook. One side of the shell usually opens to
eliminate the need for threading of the line. It is commonly
used for lifting loads on a single line or as a device to
control the position or direction, or both, of a fall line or
pulling line. Syn: Skookum, Washington, Western.
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Bonded
The mechanical interconnection of conductive parts to maintain a
common electrical potential. Syn: Connected.
Bullwheel
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A wheel incorporated as an integral part of a bullwheel puller
or tensioner to generate pulling or braking tension on
conductors or pulling lines, or both, through friction.
A puller or tensioner normally has one or more pairs of wheels
arranged in tandem incorporated in its design. The physical size
of the wheels will vary for different designs, but 17 in (43 cm)
face widths and diameters of 5 ft. (150 cm) are common. The
wheels are power driven or retarded and lined with single or
multiple groove neoprene or urethane linings. Friction is
accomplished by reeving the pulling line or conductor around the
groove of each pair.
Two-Conductor, Three-Conductor, Four-Conductor, Multiconductor
Bundle
A circuit phase consisting of more than one conductor. Each
conductor of the phase is referred to as a subconductor. A two-
conductor bundle has two subconductors per phase. These may be
arranged in a vertical or horizontal configuration. Similarly a
three-conductor bundle has three subconductors per phase. These
usually are arranged in a triangular configuration with the
vertex of the triangle up or down. A four-conductor bundle has
four subconductors per phase. These normally are arranged in a
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square configuration. Although other configurations are
possible, those listed are the most common. Syn:twin-bundle,
tri-bundle, quad-bundle.
Strand restraining Clamp
An adjustable circular clamp commonly used to keep the
individual strands of a conductor in place and to prevent them
from spreading when the conductor is cut. Syn: block, cable
binding; clamp, hose; clamp, plier; grip, vise.
Clearance
1 The condition in which a circuit has been deenergized to
enable work to be performed more safely. A clearance is
normally obtained on a circuit presenting a source of
hazard prior to starting work. Syn: outage, permit,
restriction.
2 The minimum separation between two conductors, between
conductors and supports or other objects, or between
conductors and ground or the clear space between any
objects.
Clipping-in
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The transferring of sagged conductors from the travellers to
their permanent suspension positions and the installing of the
permanent suspension clamps. Syn:Clamping-in, clipping.
Clipping Offset
A calculated distance, measured along the conductor from the
plumb mark to a point on the conductor at which the center
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of the suspension clamp is to be placed. When stringing in
rough terrain, clipping offsets may be required to balance
the horizontal forces on each suspension structure.
Conductor
A wire, or combination of wires not insulated from one
another, suitable for carrying an electric current. It may
be, however, bare or insulated. Syn: Cable, wire.
Conductor car.
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A device designed to carry workmen and ride on sagged bundle
conductors, thus enabling them to inspect the conductors for
damage and install spacers and dampers where required. These
devices may be manual or powered. Syn: Cable buggy, cable
car, spacer buggy, spacer cart, spacing bicycle. (Fig. 2.10 &
2.11)
Connector rope
A special high strength steel link used to join two lengths of
pulling rope by means of the eye splice at each end. Although
designed to pass easily through the grooves of the
bullwheels on the puller, it should not be passed under full
load. Syn: Peanut.
Crossing structure
A structure built of poles and, sometimes, rope nets. It is
used whenever conductors are being strung over roads, power
lines, communications circuits, highways, or railroads, and
is normally constructed in such a way as to prevent the
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conductor from falling onto or into any of these facilities in
the event of equipment failure, broken pulling lines, loss
of tension, etc. Syn: guard structure, H-frame, rider
structure, temporary structure.
Deenergized
Free from any electric connection to a source of potential
difference and from electric charge; not having a potential
different from that of the ground. The term is used only with
reference to current-carrying parts that are sometimes alive
(energized). To state that a circuit has been deenergized
means that the circuit has been disconnected from all
intended electrical sources. However, it could be
electrically charged through induction from energized circuits
in proximity to it, particularly if the circuits are
parallel. Syn: dead.
Dynamometer
A device designed to measure loads or tension on conductors.
Various models of these devices are used to tension guys or sag
conductors. Syn: Clock, load cell. (Fig. 2.9)
Energized
Electrically connected to a source of potential difference, or
electrically charged so as to have a potential different from
that of the ground. Syn: alive, current carrying, hot, live.
Equipotential
An identical state of electrical potential for two or more items.
Explosives
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Mixtures of solids, liquids, or a combination of the two that,
upon detonation, transform almost instantaneously into other
products that are mostly gaseous and that occupy much greater
volume than the original mixtures. This transformation generates
heat, which rapidly expands the gases, causing them to exert
enormous pressure. Dynamite and Primacord are explosives as
manufactured. Aerex, Triex, and Quadrex are manufactured in
two components and are not true explosives until mixed.
Explosives are commonly used to build construction roads, blast
holes for anchors, structure footings, etc. Syn: Aerex,
dynamite, fertilizer, power, Primacord, Quadrex, Triex.
Conductor grip
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A device designed to permit the pulling of conductor without
splicing on fittings, eyes, etc. It permits the pulling of a
continuous conductor where threading is not possible. The
designs of these grips vary considerably. Grips such as the
Klein (Chicago) and Crescent utilize an open-sided rigid body
with opposing jaws and swing latch. In addition to pulling
conductors, this type is commonly used to tension guys and,
in some cases, pull wire rope. The design of the come-along
(pocket-book, suitcase, four bolt, etc.) incorporates a bail
attached to the body of a clamp that folds to completely
surround and envelope the conductor. Bolts are then used to
close the clamp and obtain a grip. Syn: buffalo; come-along;
Crescent; four bolt; grip; grip, Chicago; Kellem; Klein;
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pocketbook; seven bolt; six bolt; slip-grip; suitcase. (Fig. 2.4)
Woven wire grip
A device designed to permit the temporary joining or pulling
of conductors without the need of special eyes, links, or
grips. Syn: basket; Chinese finger; grip, wire mesh; Kellem;
sock. (Fig. 2.6 & 2.12)
Grounded
Connected to earth or to some extended conducting body that
serves instead of the earth, whether the connection is
intentional or accidental.
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Ground grid
A system of interconnected bare conductors arranged in a
pattern over a specified area either on or buried below the
surface of the earth. Normally, it is bonded to ground rods
driven around and within its perimeter to increase its grounding
capabilities and provide convenient connection points for
grounding devices. The primary purpose of the grid is to provide
safety for workmen by limiting potential differences within its
perimeter to safe levels in case of high currents that could
flow if the circuit being worked became energized for any reason
or if an adjacent energized circuit faulted. Metallic surface
mats and gratings are sometimes utilized for this same
purpose. When used, these grids are employed at pull, tension,
and midspan splice sites. Syn: counterpoise, ground gradient
mat, ground mat.
Personal ground
A portable device designed to connect (bond) a deenergized
conductor or piece of equipment, or both, to an electrical
ground. It is utilized at the immediate site when work is to be
performed on a conductor or piece of equipment that could
accidentally become energized. Syn:ground stick; ground
working; red head.
Ground rod
A rod that is driven into the ground terminal, such as a
copper-clad rod, solid copper rod, galvanized iron rod, or
galvanized iron pipe. Copper-clad steel rods are commonly used
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during conductor stringing operations to provide a means of
obtaining an electrical ground using portable grounding devices.
Syn: ground electrode.
Running Ground
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A portable device designed to connect a moving conductor or
wire rope, or both, to an electrical ground. These devices are
normally placed on the conductor or wire rope adjacent to the
pulling and tensioning equipment located at either end of a sag
section. They are primarily used to provide safety for
personnel during construction or reconstruction operations.
Syn: ground, moving; ground roller; ground, rolling; ground,
traveling. (Fig. 2.13).
Structure base Ground
A portable device designed to connect (bond) a metal structure
to an electrical ground. It is primarily used to provide safety
for personnel during construction, reconstruction or maintenance
operations. Syn: ground, butt; ground chain; ground,
structure; ground, tower.
Traveller ground
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A portable device designed to connect a moving conductor or
wire rope, or both, to an electrical ground. It is primarily
used to provide safety for personnel during construction or
reconstruction operations. This device is placed on the
traveler (sheave, block, etc.) at a strategic location where
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an electrical ground is required. Syn: ground, block;
ground, rolling; ground, sheave.
Hoist
An apparatus for moving a load by the application of a pulling
force and not including a car or platform running in guides.
These devices are normally designed using roller or link chain
and built-in leverage to enable heavy loads to be lifted or
pulled. They are often used to deadend a conductor during
sagging and clipping in operations and during the tensioning
of guys. Syn: Chain hoist; chain tugger; Coffing hoist;
puller, drum.
Conductor lifting hook
A device resembling an open boxing glove designed to permit
the lifting of conductors from a position above them. It is
normally used during clipping-in-operations. Suspension clamps
are sometimes used for this purpose. Syn: Boxing glove,
conductor hook, lifting shoe, lip. (Fig. 2.5)
Isolated
i) Physically separated, electrically and mechanically, from
all sources of electrical energy. Such separation may not
eliminate the effects of electrical induction.
ii) An object that is not readily accessible to persons
unless special means for access are used.
Compression joint
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A tubular compression fitting designed and fabricated from
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aluminum, copper, or steel to join conductors or overhead
groundwires. It is usually applied through the use of hydraulic
or mechanical presses. However, in some cases, automatic, wedge,
and explosive-type joints are utilized. Syn:Conductor splice,
sleeve, splice.
Protector joint
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A split sleeve that fits over a conductor compression joint
used to protect the joint from bending or damage if the joint
must pass through travellers. The joint protector usually has
split rubber collars at each end to protect the conductor
from damage where it exits at each end of the sleeve.
Jumper
i) The conductor that connects the conductors on opposite
sides of a deadend structure. Syn: Deadend loop.
ii) A conductor placed across the clear space between the ends
of two conductors or metal pulling lines that are being
spliced together. Its purpose, then, is to act as a shunt
to prevent workers from accidentally placing themselves in
series between the two conductors.
Tower ladder
A ladder complete with hooks and safety chains attached to one
end of the side rails. These units are normally fabricated from
fiberglass, wood, or metal. The ladder is suspended from the arm
or bridge of a structure to enable workers to work at the
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conductor level, to hang travellers, perform clipping-in
operations, etc. In some cases, these ladders are also used
as lineperson's platforms. Syn: Ladder, hook.
Insulator lifter
A device designed to permit insulators to be lifted in a string
to their intended position on a structure. Syn:Insulator saddle,
potty seat.
Bull line
A high-strength line normally synthetic fiber rope, used for
pulling and hoisting large loads. Syn: Bull rope; line pulling;
line, threading.
Finger line
A lightweight line, normally sisal, manila, or synthetic fiber
rope, that is placed over the traveller when it is hung. It
usually extends from the ground and passes through the
traveller and back to the ground. It is used to thread the end
of the pilot line or pulling line over the traveller and
eliminates the need for workmen on the structure. These lines
are not required if pilot lines are installed when the
travellers are hung. Syn: Finger rope.
Pilot rope/line
A lightweight line, normally synthetic fiber rope, used to
pull heavier pilot wire that, in turn, are used to pull the
conductor. Pilot ropes may be installed with the aid of
finger lines or by helicopter when the insulators and
travellers are hung. Syn: Leader; line, lead; line, straw;
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P-line.
Pilot wire / Pulling line
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A high-strength line, normally wire rope, used to pull the
conductor. However, on reconstruction jobs in which a
conductor is being replaced, the old conductor often serves as
the pilot wire for the new conductor. In such cases, the old
conductor must be closely examined for any damage prior to the
pulling operations. Syn: Line, bull; line, hard; line, light;
line, sock; pulling rope.
Safety / life line
A safety device normally constructed from synthetic fiber rope
and designed to be connected between a fixed object and the body
belt of a worker working in an elevated position when his/her
regular safety strap cannot be utilized. Syn: Line, life; line,
safety; scare rope.
Tag line
A control line, normally manila or synthetic fiber rope,
attached to a suspended load to enable a worker to control its
movement. Syn: Tag rope.
Threading line
A lightweight flexible line, normally manila or synthetic
fiber rope, used to lead a conductor through the bullwheels of a
tensioner or pulling line through a bull wheel puller. Syn:
Line, bull; threading rope.
Connector Link
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A rigid link designed to connect pilot wires and conductors
together in series. It will not spin and relieve torsional
force. Syn: Bullet, connector, link, slug.
Swivel link
A swivel device designed to connect pilot wires and conductors
together in series or to connect one pulling line to the drawbar
of a pulling vehicle. The device will spin and help relieve the
torsional forces that build up in the line or conductor under
tension. Syn: Swivel.
OPGW
Concentric-lay-stranded composite conductor for use as overhead
groundwire with telecommunication capability. The conductor is
constructed with a central optical fiber core surrounded by
helically laid aluminum-clad wires, aluminum alloy wires,
galvanized steel wires, or combinations thereof.
Overhead Groundwire (OHGW) (Lightning Protection)
Multiple grounded wire or wires placed above phase conductors
for the purpose of intercepting direct strokes in order to
protect the phase conductors from the direct strokes. Syn:
Earth wire, shield wire, skywire, static wire.
Aerial Platform
A device designed to be attached to the boom tip of a crane or
aerial lift and support a worker in an elevated working
position. Platforms may be constructed with surrounding railings
that are fabricated from aluminum, steel, or fiber reinforced
plastic. Occasionally, a platform is suspended from the load
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line of a large crane. Syn: Cage, platform.
Lineperson's Platform
A device designed to be attached to a wood pole or metal
structure, or both, to serve as a supporting surface for
workers engaged in deadending operations, clipping-in,
insulator work, etc. The designs of these devices vary
considerably. Some resemble short cantilever beams, others
resemble swimming pool diving boards, and still others as long
as 40 ft. (12 m) are truss structures resembling bridges.
Materials commonly used for fabrication are wood, fiberglass,
and metal. Syn: Baker board, D-board, deadend board, dead-end
platform, diving board.
Plumb mark
A mark placed on the conductor located vertically below the
insulator point of support for steel structures and vertically
above the pole center line at ground level for wood pole
structures used as a reference to locate the center of
the suspension clamp.
Bullwheel Puller
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A device designed to pull pulling lines and conductors during
stringing operations. It normally incorporates one or more
pairs of urethane or neoprene-lined, powerdriven, single or
multiple groove bullwheels in which each pair is arranged in
tandem. Pulling is accomplished by friction generated against
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the pulling line that is reeved around the grooves of a pair
of the bullwheels. The puller is usually equipped with its
own engine, which drives the bullwheels mechanically,
hydraulically, or through a combination of both. Some of these
devices function as either a puller or tensioner.
Syn: Puller.
Drum puller
A device designed to pull a conductor during stringing
operations. It is normally equipped with its own engine, which
drives the drum mechanically, hydraulically, or through a
combination of both. It may be equipped with synthetic fiber
rope or wire rope to be used as the pulling line. The pulling
line is payed out from the unit, pulled through the travellers
in the sag section, and attached to the conductor. The conductor
is then pulled in by winding the pulling line back onto the
drum. This unit is sometimes used with synthetic fiber rope
acting as a pilot line to pull heavier pulling lines across
canyons, rivers, etc. Syn: Hoist, hoist, single drum; tugger;
winch, single drum.
Reel puller
A device designed to pull a conductor during stringing
operations. It is normally equipped with its own engine, which
drives the supporting shaft for the reel mechanically,
hydraulically, or through a combination of both. The shaft, in
turn, drives the reel. The application of this unit is
essentially the same as that for the drum puller. Some of
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these devices function as either a puller or tensioner.
Two drum, Three drum Puller
The definition and application for this unit is essentially
the same as that for the drum puller. It differs in that this
unit is equipped with two or three drums and thus can pull
one, two, or three conductors individually or simultaneously.
Syn: Hoist, double drum; hoist, triple drum; winch, double drum;
winch, three drum; winch, triple drum; winch, two drum; tugger.
Pulling vehicle
Any piece of mobile ground equipment capable of pulling pilot
lines, pulling lines, or conductors. However, helicopters may be
considered as a pulling vehicle when utilized for the same
purpose.
Reel Stand
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A device designed to support one or more conductor or groundwire
reel having the possibility of being skid,trailer, or truck
mounted. These devices may accommodate rope or conductor reels
of varying sizes and are usually equipped with reel brakes to
prevent the reels from turning when pulling is stopped. They are
used for either slack or tension stringing. The designation of
reel trailer or reel truck implies that the trailer or truck
has been equipped with a reel stand (jacks) and may serve as a
reel transport or payout unit, or both, for stringing
operations. If the reel stand is not self loading,a crane,
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forklift, or other suitable equipment is used to load the reel
into the stand. Depending upon the sizes of the reels to be
carried, the transporting vehicles may range from single-axle
trailers to semitrucks with trailers having multiple axles.
Syn: Reel Trailer, reel transporter, reel truck.
Ruling Span
A calculated span length that will have the same changes in
conductor tension due to changes of temperature and conductor
loading as will be found in a series of spans of varying lengths
between deadends.
Running Board
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A pulling device designed to permit stringing more than one
conductor simultaneously with a single pulling line. For
distribution stringing, it is usually made of lightweight tubing
with the forward end curved gently upward to provide smooth
transition over pole crossarm rollers. For transmission
stringing, the device is either made of sections hinged
transversely to the direction of pull or of a hard nose
rigid design, both having a flexible pendulum tail suspended
from the rear. This configuration stops the conductors
from twisting together and permits smooth transition over the
sheaves of bundle travellers. Syn: Alligator, bird, birdie,
equilizer pully, monkey tail, sled. (Fig. 2.7)
Sag
The distance measured vertically from a conductor to the
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straight line joining two points of support. Unless otherwise
stated, the sag referred to is at the midpoint of the span.
Sag Section
The section of line between snub structures. More than one sag
section may be required in order to sag properly the actual
length of conductor that has been strung. Syn: Pull setting,
stringing section.
Sag Span
A span selected within a sag section and used as a control to
determine the proper sag of the conductor, thus establishing
the proper conductor level and tension. A minimum of two, but
normally three, sag spans are required within a sag section in
order to sag properly. In mountainous terrain or where span
lengths vary radically, more than three sag spans could be
required within a sag section. Syn: Control Span.
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Self-damping Conductor (SDC)
ACSR that is designed to control aeolian vibration by integral
damping. Trapezoidal aluminum wires and annular gaps are
utilized. (Fig.2.3)
Shaped wire compact Conductor(TW)
ACSR or AAC that is designed to increase the aluminum area for a
given diameter of conductor by the use of trapezoidal shaped
aluminum wires.
Sheave
1) The grooved wheel of a traveller or rigging block.
Travelers are frequently referred to as sheaves. Syn:
Pulley, roller, wheel, traveller.
2) A shaft-mounted wheel used to transmit power by means of
a belt, chain, band, etc.
Pull Site
The location on the line where the puller, reel winder, and
anchors (snubs) are located. This site may also serve as the
pull or tension site for the next sag section. Syn: Reel setup,
tugger setup.
Tension Site
The location on the line where the tensioner, reel stands, and
anchors (snubs) are located. This site may also serve as the
pull or tension site for the next sag section. Syn:
Conductor payout station, payout site, reel setup.
Snub Structure
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as a zero point for sagging and clipping offset calculations.
The section of line between two such structures is the sag
section, but more than one sag section may be required in order
to sag properly the actual length of conductor that has been
strung. Syn: O structure, zero structure.
Wire rope Splice
The point at which two wire ropes are joined together. The
various methods of joining (splicing) wire ropes together
include hand tucked woven splices, compression splices that
utilize compression fittings but do not incorporate loops (eyes)
in the ends of the ropes, and mechanical splices that are made
through the use of loops (eyes) in the ends of the ropes held in
place by either compression fittings or wire rope clips. The
latter are joined together with connector links or steel bobs
and, in some cases, are rigged eye to eye. Woven splices are
often classified as short or long. A short splice varies in
length from 7 to 17 ft. (2 to 5 m) for 0.25 to 1.5 in (6 to 38
mm) diameter ropes, respectively, while a long splice varies
from 15 to 45 ft. (4 to 14 m) for the same size ropes.
Splicing Cart
A unit that is equipped with a hydraulic compressor (press) and
all other necessary equipment for performing splicing
operations on conductor. Syn: Sleeving trailer, splicing
trailer, splicing truck.
Steel Supported Aluminum Conductor (SSAC)
ACSR with the aluminum wires annealed.
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Step Voltage
The potential difference between two points on the earth's
surface separated by a distance of one pace (assumed to be 1
m) in the direction of maximum potential gradient. This
potential difference could be dangerous when current flows
through the earth or material upon which a worker is standing,
particularly under fault conditions. Syn: Step Potential.
Stringing
The pulling of pilot lines, pulling lines, and conductors over
travellers supported on structures of overhead transmission
lines. Quite often, the entire job of stringing conductors is
referred to as stringing operations, beginning with the planning
phase and terminating after the conductors have been installed
in the suspension clamps.
Slack Stringing
The method of stringing conductor slack without the use of a
tensioner. The conductor is pulled off the reel by a pulling
vehicle and is dragged along the ground, or the reel is
carried along the line on a vehicle and the conductor is
deposited on the ground. As the conductor is dragged to, or
past, each supporting structure, the conductor is placed in
the travelers, normally with the aid of finger lines.
Tension stringing
The use of pullers and tensioners to keep the conductor under
tension and positive control during the stringing phase, thus
keeping it clear of the earth and other obstacles that could
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cause damage.
Switching Surge
A transient wave of overvoltage in an electrical circuit caused
by a switching operation. When this occurs, a momentary voltage
surge could be induced in a circuit adjacent and parallel to
the switched circuit in excess of the voltage induced normally
during steady state conditions. If the adjacent circuit is
under construction, switching operations should be minimized
to reduce the possibility of hazards to the workmen.
Sag Target
A device used as a reference point to sag conductors. It is
placed on one structure of the sag span. The sagger, on the
other structure of the sag span, can use it as a reference to
determine the proper conductor sag. Syn: Sag board,target
Bullwheel Tensioner
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A device designed to hold tension against a pulling line or
conductor during the stringing phase. Normally, it consists of
one or more pairs of urethane or neoprenelined, power-braked,
single or multiple groove bullwheels in which each pair is
arranged in tandem. Tension is accomplished by friction
generated against the conductor that is reeved around the
grooves of a pair of the bullwheels. Some tensioners are
equipped with their own engines, which retard the bullwheels
mechanically, hydraulically, or through a combination of both.
Some of these devices function as either a puller or
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tensioner. Other tensioners are only equipped with friction
type retardation. Syn: Brake, retarder, tensioner.
Touch Voltage
The potential difference between a grounded metallic structure
and a point on the earth's surface separated by a distance equal
to the normal maximum horizontal reach, approximately 3 ft. (1
m). This potential difference could be dangerous and could
result from induction or fault conditions, or both. Syn: Touch
Potential.
Transit
An instrument primarily used during construction of a line to
survey the route, to set hubs and point on tangent (POT)
locations, to plumb structures, to determine downstrain angles
for locations of anchors at the pull and tension sites, and to
sag conductors. Syn: Level, scope, site marker.
Traveller
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A sheave complete with suspension arm or frame used separately
or in groups and suspended from structures to permit the
stringing of conductors. These devices are sometimes bundled
with a center drum or sheave and another traveler, and are
used to string more than one conductor simultaneously. For
protection of conductors that should not be nicked or
scratched, the sheaves are often lined with nonconductive or
semiconductive neoprene or non-conductive urethane. Any one
of these materials acts as a padding or cushion for the
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conductor as it passes over the sheave. Traveller grounds
must be used with lined travellers in order to establish
an electrical ground. Syn: Block, dolly, sheave, stringing
block, stringing sheave, stringing traveller. (Fig. 2.8)
Traveller Sling
A sling of wire rope, sometimes utilized in place of
insulators, to support the traveller during stringing
operations. Normally, it is used when insulators are not
readily available or when adverse stringing conditions
might impose severe downstrains and cause damage or complete
failure of the insulators. Syn: Choker.
Uplift roller
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A small single-grooved wheel designed to fit in or
immediately above the throat of the traveller and keep the
pulling line in the traveller groove when uplift occurs due to
stringing tensions. (Fig. 2.15)
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Reel winder
A device designed to serve as a recovery unit for a pulling
line. It is normally equipped with its own engine, which drives
a supporting shaft for a reel mechanically, hydraulically, or
through a combination of both. The shaft, in turn, drives the
reel. It is normally used to rewind a pulling line as it
leaves the bullwheel puller during stringing operations. This
unit is not intended to serve as a puller, but sometimes
serves this functions where only low tensions are involved. Syn:
Takeup Reel.
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Chapter-3
Stringing Methods & General Aspects
______________________________________________________________________
CHAPTER THREE
______________________________________________________________________
Stringing Methods & General Aspects
Back to Contents Page
3.1 Methods of stringing .
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There are basically two methods of stringing. These are
i) Slack or Manual methods
ii) Tension method
3.1.1 Manual method :
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Using this method, the conductor is pulled along the
ground by means of a pulling vehicle,or the drum is
carried along the line on a vehicle and the conductor
is deposited on the ground. The conductor drums are
positioned on drum stands or jacks, either placed on
the ground or mounted on a transporting vehicle. These
stands are designed to support the drum on an arbor,
thus permitting it to turn as the conductor is pulled
out. Usually, a braking device is provided to
prevent overrunning and backlash. When the conductor
is dragged past a supporting structure, pulling is
stopped and the conductor is placed in travelers
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attached to the structure before proceeding to the
next structure.
This method is chiefly applicable to the construction
of new lines in cases in which maintenance of
conductor surface condition is not critical and where
terrain is easily accessible to a pulling vehicle. The
method is not usually economically applicable in urban
locations where hazards exist from traffic or where
there is danger of contact with energized circuits,
nor it is practical in mountainous regions
inaccessible to pulling vehicles.
3.1.2 Tension Method :
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Using this method, the conductor is kept under
tension during the stringing process. Normally, this
method is used to keep the conductor clear of the
ground and obstacles, which might cause conductor
surface damage and clear of energized circuits. It
requires the pulling of a light pilot line into the
travelers, which in turn is used to pull in a heavier
pulling line. The pulling line is then used to pull
in the conductors from the drum stands using specially
designed tensioners and pullers. For lighter
conductors, a lightweight pulling line may be used in
place of the pilot line to directly pull in the
conductor. A helicopter or ground vehicle can be used
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to pull or lay out a pilot line or pulling line.
Where a helicopter is used to pull out a line,
synthetic rope is normally used to attach the line
to the helicopter and prevent the pulling or pilot
line from flipping into the rotor blades upon release.
The tension method of stringing is applicable where it
is desired to keep the conductor off the ground to
minimize surface damage or in areas where frequent
crossings are encountered. The amount of right-of-way
travel by heavy equipment is also reduced. Usually,
this method provides the most economical means of
stringing conductor. The helicopter use is
particularly advantageous in rugged or poorly
accessible terrain.
3.2 Grounding during stringing
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3.2.1 Introduction :
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For any given situation, the bonding together of all
equipment and electrical grounds in a common array is
of major importance. However, such bonding offers no
assurance that a hazardous potential will not exist
between the bonded items and the earth. It is
impractical to design a grounding system precisely
around available fault currents or calculated effects.
Such a design would require precise knowledge of
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many variables and would result in a different
grounding scheme for each location.
The degree of grounding protection required for a
given construction project is dependent upon the
exposure to electrical hazards that exist within the
project area. For a project remote from other lines
and at a time of low probable thunderstorm activity,
minimal grounding requirements are in order. Minimum
grounding requirements include bonding and grounding
of all machines involved in stringing of the
conductor, pulling line, or pilot line. In addition,
running grounds should be installed on all conductive
lines in front of the pulling and tensioning
equipment.
On the contrary, for a project in congested area with
exposure to numerous parallel lines and crossing
situations, and with probability of thunderstorm
activity and adverse weather conditions, extensive
grounding requirements are called for. Historically,
the most significant hazard results from work in
proximity to energized lines. Under any circumstance,
in addition to open jumpers, grounding and other
protective measures must be employed to ensure
reasonable and adequate protection to all personnel.
In addition to the grounding system, the best
safety precaution is to respect all equipment as if it
could become energized. The degree of protection Vol.5 : Page #
provided for a specific project must be a decision of
project supervision based on a clear understanding
of the potential hazards.
3.2.2 Source of Hazards :
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Electrical charges may appear on a line due to one or
more of the following factors.
i) Charges induced on the line by a
neighboring energized line.
ii) A fault caused by an accidental contact or
flashover between the line and a neighboring
energized line.
iii) Induced static charge due to atmospheric
conditions.
iv) An error in which the line is accidentally
energized.
v) A lightning strike to the line.
3.2.3 Grounding procedure :
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Grounding cables must be connected to the ground
source first, then to the object being grounded. When
removing grounds, the ground must be removed from the
grounded object first and then from the ground source.
The object being grounded should not be teased with
the ground clamp. The clamp must be poised by the
object, snapped on quickly and firmly, and tightened.
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If an arc is drawn, the clamp should not be withdrawn,
but should be kept on the conductor, thus grounding
the line.
3.3 Communications
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3.3.1 Slack stringing requires a minimum of communications.
It is, however, desirable to have communication
between the pulling vehicle and the personnel at the
drum location.
3.3.2 Tension stringing requires good communications
between the personnel at the tensioner end and those
at the puller end and at intermediate check points
at all times during the stringing operation. During
the stringing of bundled conductors with a running
board, it is desirable to observe the running board
as it passes through each traveler. The running
board observer(s) should have reliable communications
with both pulling and tensioning ends. When following
the board from the ground is not practical, this can
be accomplished with the aid of helicopters.
3.3.3 During helicopter stringing of the pilot line or
conductor, reliable radio contact with all ground
work sites is extremely important.
Dual or backup systems of communication, with a
dedicated single-use frequency, should be available in
case one system fails, particularly during the actual
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stringing operation.
3.4 Special requirements for mobile equipment :
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3.4.1 Drum or reel Stand.
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Drum stands are designed to be used with tensioners to
supply the necessary back tension to the conductor.
The stand(s) are selected to accommodate the conductor
(or groundwire) reel dimensions and gross weight.
Some drums are not designed to withstand the forces
developed by braking during tension stringing
operations. Direct tension stringing from the drum at
transmission line stringing tensions should not be
attempted. The conductor may be pulled directly from
the drum stand when employing slack stringing methods.
If the drum stand is not self loading, a crane,
forklift, or other suitable equipment is used to load
the drum into the stand.
3.4.2 Tensioner Bullwheel Characteristics.
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The depth, Dg, and flare of grooves in the bullwheels
are not critical. Semicircular grooves with depths in
the order of 0.5 or more times the conductor diameter
and with flare angles in the order of 5° to 15° from
the vertical generally have been found to be
satisfactory.
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The number of grooves in the bullwheel must be
sufficient to prevent the outer layer of wires of
multilayer conductors from slipping over underlying
layers. The minimum diameter of the bottom of the
grooves, Db, should be 30 to 40 times the diameter of
conductor. Details are shown in fig - 3.1.
Tandem bullwheels should be so aligned that the
offset will be approximately one-half the groove
spacing. For normal conductors having a right-hand
direction of lay for the outer wires, bullwheels
should be arranged so that, when facing in the
direction of pull, the conductor will enter the
bullwheel on the left and pull off from the right side
as shown in fig. 3.1. For any conductors having a
left hand direction of lay for the outer wires, the
conductor should enter on the right and pull off from
the left. This arrangement is necessary to avoid any
tendency to loosen the outer layer of strands as the
conductor passes over the bullwheels. Similarly
stranded conductor or wire should be wound on a drum
according to the lay and direction of travel. Note
the convenient thumb rule as shown in Fig.3.2.Clench
the hand into a fist, with the thumb and index finger
protruding. Use the right hand for right lay and the
left hand for left lay. The clenched fingers
represent the barrel and the index finger the
direction of pull off. The thumb points to the Vol.5 : Page #
proper attachment site.
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The material and finish of the grooves must be such
as not to mar the surface of the conductor. Elast-
omer lined grooves are recommended for all
conductors, but are particularly important for
nonspecular conductors. Should a semiconducting
elastomer be used for lining the grooves, it should
not be relied upon for grounding.
Difficulties have been experienced with single V-
groove type bullwheels on some multilayer and special
construction conductors. These types of bullwheels
should only be used with the concurrence of the
conductor manufacturer.
3.4.3 Puller and tensioner operating characteristics.
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The pulling and braking systems should operate
smoothly and should not cause any sudden jerking or
bouncing of the conductor. Each system should be
readily controllable and capable of maintaining a
constant tension.
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Pullers and tensioners may be mounted separately or in
groups for bundled conductor installation. The
controls should allow the independent adjustment of
tension in each conductor. It is recommended that the
tensioner have an independently operated set of
bullwheels for each subconductor when stringing
bundled conductor, particularly when more than two
subconductors per phase are being installed. Pullers
should be equipped with load indicating and limiting
devices. The load limiting device should automatically
stop the puller from acting further if a preset
maximum load has been exceeded. Tensioners should be
equipped with tension indicating devices.
Capacity selection of the puller and tensioner is
dependent upon conductor weight, the length to be
strung, and the stringing tensions. The capacities of
the puller and tensioner should be based on the
conductor, span length, terrain, and clearances
required above obstructions. In general, stringing
tensions will be about 50% of sag tensions. Sag
tensions should never be exceeded during stringing.
There are basically two types of pulling machines
used in the construction of transmission lines being
strung under tension. These are defined as bullwheel
and drum type or reel type pullers. Some drum-type or
reel type pullers are available with level wind
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features to provide uniform winding of the line. Some
drum-type and all reel-type pullers provide easy
removal of the drum (or reel) and line to facilitate
highway mobility. This feature also provides the
advantage of interchangeability of drums. The control
of payout tension of the pulling line is a desirable
feature of many pullers. Mobility of the pullers and
tensioners is important to minimize downtime between
pulls. Also critical are the setup and leveling
features of the units.
3.5 Travelers
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3.5.1 Diameter. It is generally recognized that as sheave
diameters are made larger, the following advantages
are gained:
(i) The radius bending of the conductor is increased,
so the amount of strain and the amount of
relative movement between individual wires in
the conductor are reduced. This, in turn, reduces
the amount of energy required to bend and
straighten the conductor as it passes through the
travelers. The force and energy required for
such bending and straightening regards the
passage of the conductor in much the same way as
friction in the bearing of the travelers.
(ii) The bearing pressures between conductor strand
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layers are reduced, thus reducing potential
conductor internal strand damage. This is
commonly known as strand notching.
(iii)The force required to overcome friction in the
bearings is reduced because of the greater moment
arm for turning.
(iv) The number of rotations and speed of rotation
are reduced, so wear on the bearings and grooves
is alleviated.
(v) The obvious disadvantages of larger sheaves are
cost and added weight.
The minimum sheave diameter, Ds, at the bottom of
the groove, as shown in Fig 3.3, should be
satisfactory for typical conductor stringing
operations. However, for stringing conductors in
excess of approximately 3km or over substantially
uneven terrain, the recommended minimum bottom
groove diameter of sheaves is (20 Dc-4) inches
([20Dc-10]cm) orlarger, where Dc stands for
conductor diameter. In exceptionally arduous
circumstances, accurate sagging may some times
be very difficult with sheaves having diameters
of less than 19 Dc or 20 Dc.
3.5.2 Configuration of Groove.
The minimum radius at the base of the groove, Rg, is
recommended to be 1.10 times the radius of the
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conductor as shown in Fig 3.3.
Sheaves having a groove radius as discussed above
may, with limitations, be used with smaller
conductors. The limitations relate to the number of
layer of aluminum wires in the conductor. The more
layers of aluminum wires, the more important it is to
support the conductor with a well-fitting groove.
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The depth of groove, Dg, should be a minimum of 25% greater than
the diameter of the conductor. The sides of the groove
should flare between 12° and 20° form the vertical to
facilitate the passage of swivels, grips etc., and to
contain the conductor within the groove, particularly
at line angles.
3.5.3 Bearings.
The bearings should preferably be ball or roller type
with adequate provisions for lubrication and
shielding against contamination. The lubricant must
be suitable for the temperature range involved; and,
where sealed bearings are not used, care should be
taken to ensure subsequent lubrication with the same
type of grease. Mixing of greases of different types
(that is, lithium base and calcium base) may cause
degradation of the lubricant and subsequent bearing
failure. Bearings should have sufficient capacity to
withstand running or static loads without damage.
Proper maintenance is essential.
3.5.4 Material and Construction.
Travelers may be of any suitable material, with due
consideration given to weight. Unlined sheaves for
stringing aluminum conductors should be made of
aluminum or magnesium alloy, and the grooves should
have a smooth, polished finish. It is recommended
that the manufacturer's safe working load, or other
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identification to enable determination of such load,
be permanently displayed on the traveler. Always
ensure that the manufacturer's safe working load for
the traveler is not exceeded. This is particularly
important for situations in which travelers are used
on heavy line angles or on the first or last towers
at which the conductor comes to ground level.
Maximum loads usually will result when the conductor
is being pulled up to sag tensions.
It is recommended that clearances between the sheave
(s) and frame, particularly in the traveler throat
area, be kept as small as possible. This will prevent
the pilot line from jamming should the pilot line
come out of the pulling line sheave. It is
recommended that the vertical throat opening of the
stringing block be kept as small as possible while
still allowing the safe passage of the pulling line,
swivels, and the running board. This practice will
minimize the distance the conductors need to be
lifted during the clipping-in operation.
For bundle conductor configurations, the traveler
frame and shaft should be sufficiently sized so that
deflection due to load, particularly during the
sagging operation, does not cause adjacent sheaves to
contact. Excessive deflection can cause difficulty
in sagging individual conductors.
3.5.5 Lining. Vol.5 : Page #
While grooves may be unlined or lined, lining with
elastomer provides cushioning to increase bearing area
and precludes damage to the conductor from scratched
or marred groove surfaces. Steel pulling lines are
likely to scratch or mar the surface or unlined
grooves; therefore, when such lines are to be used in
the same groove as conductor, grooves definitely
should be lined. It is generally recommended that all
sheaves be lined. It is recommended that the total
surface of the groove, including the top lip, be
lined to give maximum protection to the conductor.
The elastomer used for sheave linings should be
capable of withstanding all anticipated temperatures
without becoming brittle or developing semipermanent
flat areas. It should be sufficiently hard to
prevent the conductor from climbing up the side of
the groove.
3.5.6 Electrical Characteristics.
Neither lined nor unlined travelers should be relied
on for grounding the conductor being installed.
Greased bearings do not provide necessary conductivity
and may be damaged by relatively small currents
passing from the sheave to the body of the traveler.
Semiconductive linings, commonly referred to as
conductive linings, tested to date are reported burned
with currents as low as 20 mA.
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The induced electrical charges on conductor and
pulling lines, particularly when stringing in the
proximity of energized lines, must be drained off
with traveler grounds that bypass the linings or
greased bearings, or both. Traveler grounds provide a
means to bypass electrically the sheaves and ground
the conductor directly to a ground source. After any
grounding device has experienced fault current, it
should not be used.
3.5.7 Bundled Configurations.
Bundle conductor type travelers for stringing two or
more subconductors simultaneously require special
considerations. When even numbers of conductors are
strung, a symmetrical arrangement may be used with an
equal number of conductors on each side of the
pulling line. An independent center sheave is
provided only for the pulling line and should be of
suitable material to withstand the abrasion of the
pulling line.
When odd numbers of subconductors are strung, the
center one could follow the pulling line in the center
sheave. However, this is usually not desirable
because of the material of the groove or because of
contaminants deposited in this groove by the
pulling line, or because of both. Offset-type bundle
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conductor travelers are used that balance the load by
properly spacing the even and odd number(s) of
conductors on each side of the pulling force.
These travelers are directional and should be color-
coded. Care should be taken to ensure their proper
orientation.
When multiple conductors are strung in bundled
conductor type travelers, reduced horizontal
spacing between grooves can result in conductor
oscillation, even in a very light crosswind, too
severe to permit satisfactory sagging. (For
example, groove spacing of 5.4 conductor diameters
permitted sagging of conductors in a crosswind
condition that repeatedly prevented sagging with a
groove spacing of 2.7 conductor diameters because
of very active conductor oscillation.)
When stringing multiple conductors around line angles
in excess of 5°, bundle conductor travelers are
required until the running board passes through the
traveler, but should be replaced prior to sagging
with single-type travelers to provide proper wire
length in the clipped-in position. It is desirable
during sagging for the horizontal spacing of the
sheaves to match the final subconductor spacing to
aid in preventing subconductor sag mismatch.
Some bundle conductor travelers may be converted to
single conductor type travelers. Vol.5 : Page #
Multisheave bundle conductor type travelers and
running boards must be designed to complement each
other and work in unison. Running boards should only
be used to pull in conductors. They should be not
used to line up the conductors with an anchor (that
is, running boards should be not pulled sideways.)
Running boards should have their safe working load
displayed. It is recommended that all running boards
and swivel links be proof tested to 50% over the safe
working load. During stringing, normal pulling
speeds should be maintained when the running board
approaches a traveler.
3.5.8 Helicopter Travelers.
Helicopter travelers utilize outrigger arms that
guide the pilot line into the throat area of the
traveler. These outriggers are usually brightly
painted to be easily seen from the air. Spring-
loaded gates are employed to contain the line. For
bundle conductor travelers, additional guides may be
utilized to funnel the lines into the proper groove.
The design of helicopter travelers should be such
that personnel are not required on the structure
during placement of the pilot line. After initial
placement of the line by helicopter, normal stringing
practices are employed.
Helicopter travelers are directional, and care must Vol.5 : Page #
be exercised to orient them properly on the
structures. Due to the rotor wash of the helicopter ,
if the attachment method of travelers does not
prevent twisting, yaw bars should be utilized for
this purpose.
Some standard travelers may be converted to
helicopter type by the addition of accessory parts.
3.5.9 Uplift Rollers and Hold-Down Blocks.
Uplift rollers that attach to the traveler or hold-
down blocks that are separate devices must be used at
positions where uplift might occur. Uplift can occur
with the pulling line during the stringing operation,
due to its higher tension to weight ratio and, thus,
much flatter sag. This condition is most likely to
occur in hilly terrain at the towers in the low
points of the pull. Hold-down blocks or uplift
rollers should be used in these cases. Since the
uplift condition will normally stop when the
conductors(s) arrive, hold-down blocks that can be
removed prior to the arrival of the conductor(s)
without stopping the pulling should be used. Uplift
devices that attach to bundle travelers are usually
directional, and are usually positioned towards the
pulling end. These devices should have a
breakaway feature in the event of fouling of the
pulling line or incorrect installation.
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Chapter-4
Stringing Procedure
______________________________________________________________________
CHAPTER FOUR
______________________________________________________________________
STRINGING PROCEDURE
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4.1 Steps of stringing :
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The stringing procedure is broadly divided into the
following steps.
i) Paying out & stringing of earth wire.
ii) Paying out & stringing of conductor.
iii) Final sagging of earthwire & conductor.
iv) Regulation.
v) Clipping and fixing of accessories.
4.2 Stringing of Earthwire
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4.2.1 Paying out of earthwire
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Normally stringing of earthwire is done manually
since handling the earthwire is easy and it does not
get damaged easily. First, earthwire rollers are
provided on the earth peaks of all the suspension
towers in the section. Before hoisting of earthwire
rollers, it may be ensured that the rollers are free Vol.5 : Page #
from friction. This will ensure correct sag as
measured during sagging operation to be available
after transferring to the suspension clamp. A
lineman/ fitter may be kept on each tower to
ensure free running of the rollers with a red &
green flag and whistle.
At the starting end of a section, earthwire reel is
mounted on roller jacks or horizontal turn table.
The earthwire is pulled from tower to tower manually
or by using a tractor. After reaching the next tower
the earthwire is passed through the suspended
earthwire rollers with the help of a polypropylene
rope and paying out is continued further. Care should
be taken that the earthwire is not pulled over
rocks, stones, boulders etc. to avid scratches on its
surface.
After one length of earthwire reel is exhausted, the
second length of wire is paid out for the balance
section. Midspan joint for earthwire is compressed
on the ground joining the two lengths.
4.2.2 Jointing of earthwire :
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Midspan joints for earthwire consists of a galvanised
MS tube with internal diameter matching with the
outer diameter of earthwire. An aluminum sleeve is
provided over the MS sleeve with end plugs as a
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protective cover to avoid rusting. Relevant approved
drawings are referred for the details.
The aluminium sleeve and one plug are first inserted
through one end of the earthwire. The other plug and
steel sleeve are inserted to the other end. The
cutting of the earthwire is done after gripping the
earthwire with binding wire say 25 mm away from the
edge. The binding wire shall be removed after the
edge is inserted into the tube.
The cut edge of the wire shall be free from burring of
edges. The ends of the wires are inserted into the sleeve
equal in length from both sides. This can be ensured
by marking half the length of the steel sleeve on
both ends of the earthwire. The compression is done
with the help of a hydraulic compressor using suitable
sized dies to a compression of 100 T/sqare inch. The
compression should start from the centre of the tube
and continued progressively outwards. After
compressing the steel portion, the length & cross
section of the compressed portion shall be checked
for elongation and dia as recommended by the
manufacturer.
All sharp edges on the surface of the joint shall be
filed off and smoothened. The aluminum sleeve is
passed over steel portion and end plugs are inserted
at both ends. The compression is done with suitable
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size dies similarly as explained above for steel
portion and the surface is smoothened and length &
cross section of the compressed joint verified with
drawings.
Similar practice is used for compression of dead end
cone and earthwire jumper cones. In case any crack in
any one of the 7 strands is observed, a joint should
be provided. Any sharp kink in the earthwire should
be cut and joined with a midspan joint.
4.2.3 Sagging and final tensioning
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After paying out the earthwire over the length of the
section, one end of the earthwire is connected to the
earth peak of the tower with compressed dead end
cone.
From the tension tower on the other side of the
section, the earthwire is pulled to a rough tension
less than final tension. By holding the earthwire at
this tension on the ground, bolted come-along clamps
are fixed to the earthwire at a distance of about 60
mtrs (depending on the rough sag condition and height
of tower this may be varied) from the sagging tower.
The come-along clamp is connected with 10 or 12mm
dia steel wire rope through a set of two sheave
pulleys and the wire rope is passed through a set of
single sheave pulleys along the body of the tower to
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a hand operated winch installed on the leg of the
tower. The earthwire is tensioned by pulling the wire
rope initially by a Tractor until approximate sag is
achieved. Finally, the rope is pulled through the
hand winch to the correct sag of the earth wire. The
free end of the earthwire hanging from the come-along
clamp is picked up and passed through a pulley placed
on the earthwire peak of the tower.
The free end is pulled along the catenary curve of
wire rope from the come-along clamp to the earth
peak making provision for the length of tension clamp
with dead end cone. This point is marked by an
adhesive tape/wire and the free end of the wire
is brought down. The earthwire is cut at the marking
and the dead end cone is compressed. The compressed
cone is hoisted to the earthwire peak by
connecting a polypropylene rope passed through
pulley at the earthwire peak.
The hand winch is further tightened to pull up some
more earthwire length to facilitate bolting of the
tension cone to the earth peak. The hand winch is
released and the pulleys wire ropes and come-along
clamps are removed. Suitable adjustment in the aerial
roller can be done to equalize the length or any
difference can be considered while measuring the sag
board elevation. The method of sagging by placement
of sag board is explained in the sagging operation of Vol.5 : Page #
conductor which in principle is similar and can be
adopted for the earthwire also.
4.2.4 Clipping
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After final sagging is completed, the earthwire has
to be transferred from the aerial rollers on the
suspension towers to the earthwire suspension clamps.
The point where the earthwire touches the aerial
roller pulley is marked for fixing the suspension
clamp in correct vertical position.
The earthwire is lifted from roller by means of a
ratchet hoist/pull lift from the earthwire peak of
the tower and roller is removed. The earthwire clamp
is fixed to the tower body by D shackle and then the
centre of the earthwire clamp is matched with the
marked point of the earthwire. The saddle of the
clamp is tightened with U bolts. The lever hoist is
released to let the earthwire freely hang in the
suspension clamp.
It should be ensured that the length of the
suspension clamp from the suspension cotter of the
earthwire peak to the saddle where earthwire finally
rests should be equal to the length of the aerial
roller from cotter of earthwire peak to the top side
groove of the pulley wheel.
4.2.5 Fixing of hardware accessories
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Earthwire is provided with stock bridge type
vibration dampers. The no. of dampers to be fixed
on either side of the tension/suspension tower and
the distance from the suspension clamp/tension cone
is adopted as per manufacturer's recommendations
depending upon the span length. The operation of
fixing of vibration dampers should be taken up
immediately after fixing of suspension clamps.
Flexible copper bonds are provided to connect the
earthwire to the tower body, to improve conductivity
to earth. For each suspension/tension clamp one FCB
is provided. As copper bond is theft prone, it is
better if this is fixed just before charging of line.
At tension towers, the tension clamps on both sides
of earthwire peak are joined by an earthwire jumper,
compressed at both ends by galvanised jumper cone
for maintaining the continuity of the earthwire
between the two substations.
The length of the earthwire reels normally
manufactured is around 2000 mtrs. For stringing in
normal sections, midspan joints are used in reaches
exceeding 2000 mtrs length. But in river crossing
sections for major rivers, the midspan joint in
earthwire is not recommended due to the difficulty in
restringing in case of failure of joint. Special
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reels of about 4000 mtrs length have to be procured
for this purpose.
4.3 Stringing of conductor
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4.3.1 Guying of Towers
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Before commencement of stringing, the angle towers
where the stringing is to be started have to be
provided with guy supports for all the three phases.
The guys used generally are 20mm steel wire rope. The
guys are attached to the tower at the tip of the
cross arms and centre of the bridge, to the strain
plates with suitable D shackles.
The guys are anchored in the ground at an angle of 45
degrees or less from the horizon, attached to dead
end anchors. For making dead end anchors in the
ground, pits of 1.5mx0.6m, for a depth of 1.5m can be
dug. A set of steel beam and channels as shown in
fig.4.1 tied in the centre with 16mm wire rope, is
lowered and the pit is back filled while compacting.
The guy wire is attached to the dead end anchor wire
with the help of turn buckles of 10 tonnes capacity.
Alternately, instead of burried ground anchors, a
dead weights of sag 5 to 10 tonnes can be placed on
the ground and sag wire attached to them securely.
After pulling up the slackness in the guy, it is
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tightened by the turn buckle. Excessive tightening of
the guy should be avoided. It is advisable to tighten
the guy progressively at the time of rough sagging of
the conductor.
4.3.2 Insulator hoisting :
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4.3.2.1 Transportation of Insulators
The required no. of insulators shall be transported
to the tower locations with the wooden packing.
In case the packing is found to be worn out, fresh
packing has to be done in order to avoid damages
during transport.
The crates shall be opened at the tower location. The
Insulator hoisting is done well in advance of
commencement of paying out operation. Hence,
transport should be completed before commencement of
paying out.
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In 400 KV S.C suspension towers, single suspension I string
120 KN disc Insulators are used. For middle phase,
we use V strings consisting of 2 strings of 90 KN
insulators suspended from both ends of the bridge and
joined in the centre by Yoke plate. Recently, V
strings for all the three phases are being used in
400KV single and double circuit suspension towers.
For tension towers, double tension string is used.
All the insulator strings consist of 23 no. of discs
in series. At major river crossings for suspension
towers double suspension strings are being utilised
for reasons of more safety.
4.3.2.2 Hoisting
After opening of the crates, insulators shall be laid
in series, on wooden planks below the suspension
points. The insulators shall be cleaned with water
and wiped dry with clean cloth free from grease and
oil. Insulators shall be checked for any chipping or
crack and shall be replaced with new one if found
defective. The no. of insulators required for string
shall be joined and `R' clips in the clevis shall be
expanded to avoid slippage of the pin. 4 to 6
insulators are generally joined at the manufacturer's
works and packed in a crate. The joints of all
insulators should be checked and `R' clips should be
expanded. If any `R' clip is missing, the same is to
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be made good. The hardware of the string on the tower
side is assembled and joined to the first insulator
by ball eye. The details of hardware fitting for
suspension fitting are given in fig 4.2. The bottom
insulator is joined to the twin moose aerial roller.
The 3 wheels of the aerial rollers should be checked
for free running.
The neoprene rubber cushion on the outer rollers
shall be checked for any cracks/wearing out and shall
be changed if required.
As mentioned earlier the position of the conductor in
the centre of suspension clamp of the fitting shall
be matching with the position in the roller grooves.
Necessary adjustment shall be made in the length of
the aerial roller connector as required.
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A single sheave pulley is fixed to the cross arm very near to
the suspension hanger. A 20 mm polypropylene rope is
passed through the pulley and both the ends are
brought to the ground. One end of the rope is
firmly tied below the 3rd or 4th insulator. The
complete string with aerial roller is lifted up by
pulling the rope through a pulley attached to one of
the tower legs by using tractor/manually. Fig.4.3
shows the hoisting of insulators with tension
fittings. After reaching the top the string is
attached to the suspension hanger and string is
released slowly to hang free.
In hoisting the V string for centre phase, the method
is in general same but 2 pulleys are to be attached
near the suspension point of the V string and a rope
is attached to pull side ways and keep the string
away from the tower until it is clear of the the
waist level. Before hoisting of the V string, both
the strings are joined in the centre by yoke plate
and the aerial roller is suspended from the centre of
the yoke plate.
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4.3.3 Paying out of pilot wire
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In tension stringing, a pilot wire is used to pull
the conductor. The pilot wire is initially laid
through the centre wheel of the aerial roller.
A 12 mm dia pilot wire is generally used for pulling
of twin moose ACSR conductor. The pilot wire can be
laid length by length and joined with pilot wire
connectors or it can be pulled from one side of the
section after each drum is paid out.
At power line crossings, the pilot wire is laid from
both sides and free ends are joined after obtaining
the shutdown of the powerline. Scaffoldings shall be
provided for P&T and road crossings before paying out
of the pilot wire.
4.3.4 Position of tensioner and puller :
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The paying out of conductor is done generally between
two tension towers. The puller machine can be
positioned behind the tension tower on one side and
the tensioner in front of the tension tower on the
other side. The entry of the pilot wire into the
bull wheels of the puller machine and running out
from tensioner machine should be as nearly horizontal
as possible. Both the machines should be securely
anchored with two dead end anchors in the ground
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and slackness is removed in the stay. Reel winder
shall be positioned at convenient distance of say 10
to 15 mtrs behind the puller. Conductor drums have
to be transported to the tensioner site as per the
approved drum schedule for the section to avoid
wastage and small bit lengths being left over.
For twin moose stringing of one phase, two conductor
drums are mounted on two roller jacks. The selection
of drum shall be such that no midspan joint will come
within 30 mtrs of any tower.
The placement of drum jacks should be such that the
lateral angle of conductor approach into the bull
wheel through guide rollers is low enough to avoid
rubbing on the sides and creating loosening of the
outer strands and birdcaging. The distance of the
drums from the tensioner shall be at least 25 to 30
mtrs so as to distribute the effect of sliding of
outer strands due to low back tension. The reel
should be positioned so that it will rotate in the
same direction as the bull wheels.
4.3.5 Paying out of conductor :
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For passing the conductor through the bull wheels of
the tensioner, a 25 mm polypropylene rope is initially
wound over each bull wheel pair in the same way as the
conductor will pass during running. The ropes are
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connected to the conductors. The conductor run shall
be from the top side of the drum. The rope is pulled
by starting the tensioner at low pay out tension to
pass the conductor through bull wheels and are
brought out through the guide rollers. The sub
conductors are attached to the equalizer
pulley/running board by means of wire
mesh/endsocks and swivel joints. The pilot wire is
attached to the other end of the running board with
swivel joint.
At the puller site, the pilot wire is pulled to
remove all slackness using the reel winder. The wire
is passed through bull wheels of the puller and
connected to the reel winder machine. The tensioner
can be initially set for a tension of 2 to 2.5
tonnes. Caution should be made over the wireless hand
set to all the staff who are at middle points and to
the tensioner operator that pulling is about to be
started so that they can stay clear of pilot wire.
The puller is started to draw up the pilot wire until
the bull wheels of the tensioner start moving.
Fig.4.4 & 4.5 show paying out of Bundle conductors
with tensioner and puller. Care should be taken that
the pilot wire does not get entangled in trees,
scaffoldings, aerial rollers etc. while going up
during tensioning. This can be monitored by the staff
who are posted in between the section and guiding the Vol.5 : Page #
puller operator over the wireless sets. The pulling
of the conductor may be done at a moderate speed
while the running board is passing through the aerial
rollers.
The tension in the tensioner must be adjusted so that
the conductors travel well over the ground. In long
spans where conductor is likely to touch the ground,
ground rollers may be placed so that the conductor
can pass without any scratches.
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The back tension of the conductor behind the tensioner
has to be maintained as per the requirement of the
tensioner deployed. The back tension is adjusted by
means of brakes provided on the drum jack. A running
ground shall be connected to the conductor and pilot
wire before paying out near the tensioner and puller
which shall be earthed at the nearest tower.
Both the sub-conductors of one phase which are to be
pulled should be from the same supplier/manufacturer
and preferably from the same lot. This will help
avoid different conductor sag characteristics.
The speed of pulling of the conductor should be such
that to achieve smooth operation. Slower speeds may
cause significant swinging of the running blocks and
insulator hardware assemblies. Higher speeds can
create greater damage in case of malfunction.
The tension applied during stringing generally is
about half the sagging tension. When long lengths of
conductors are strung, the tension at the puller may
be higher than that at tensioner due to the length of
conductor strung, number and performance of
travellers, differences in elevation of supporting
structures etc.
Light and steady back tension should be maintained on
the conductor reels at all times sufficient to
prevent over-run in case of sudden stoppage.
It must also be sufficient to cause the conductor to Vol.5 : Page #
lie snugly in the first groove of the bull wheel to
prevent slack in the conductor between bull wheels.
It may be necessary periodically to loosen the brake
on the reel stand as the conductor is paid off.
Fig.4.6 indicates paid out bundle conductors.
As the conductor is unwound from the reel and
straightens out, the outer strands become loose, a
condition that is particularly noticeable in large
diameter conductor and can be best observed at the
point at which it leaves the reel. As the conductor
enters the bull wheel groove, the pressure of contact
tends to push the loose outer strands back towards
the reel where the looseness accumulates, leading to
a condition commonly known as bird caging. If this
condition is not controlled, the strands can get
damaged to the extent that the damaged conductor has
to be cut and removed.
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This problem can be remedied by allowing enough
distance between the reel and tensioner to permit the
strand looseness to distribute along the intervening
length of conductor and simultaneously maintaining
enough back tension on the reel to stretch the core
and inner strands to sufficiently tighten the outer
strands.
Sub conductor oscillation or clashing of conductors
may occur in bundled conductor lines. Temporary
spacers or other means may be required to prevent
damage of conductor surfaces prior to installation of
spacers. Temporarily positioning of one sub conductor
above another is to be avoided as different tensions
may produce sub conductor mismatch unless the
tensions are low and duration short enough so that
creep does not set in. Conductor clashing can damage
the strands and produce slivers which can result
in radio noise generation.
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Platforms shall be erected with sturdy bellies, where
roads, rivulets, channels, telecommunication or overhead power
lines, railway lines, etc. have to be crossed during stringing
operations. It shall be seen that normal services are not
interrupted or damage caused to property.
4.3.6 Repairing of conductor :
Back to Contents Page
Repairs to conductors, in the event of damage being
caused to isolated strands of a conductor during the
course of erection, if necessary, shall be carried out
during the running out operations, with repair
sleeves. Repairing of conductor surface shall be done
only in case of minor damage,scuff marks etc. keeping
in view both electrical and mechanical safe
requirements. Repair sleeves may be used when the
damage is limited to the outer most layer of the
conductor and is equivalent to not more than one
sixth of the strands of the outer most layer.
4.3.7 Jointing of conductor :
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Just before one length of the conductor paying out is
completed another drum has to be deployed in advance
beside the first drum. The paying out has to be
stopped by braking the tensioner and stopping the
puller simultaneously. The paid out conductor of
first drum is held with bolted come-along clamps at a
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distance of 40 to 50 mtrs from the tensioner. The
come- along clamps are attached to the ground anchor
stays. The conductor of the first drum is held and the
free end is cut. The free end of the second drum is
also prepared.
The two ends are joined with a wire mesh midspan
socks. The paying out is again started by releasing
the come along clamps until the midspan socks emerges
outside the tensioner and pulling is stopped. After
anchoring, the conductor is slowly drawn out from the
two end socks. The midspan socks is removed and
midspan compression joint is made. Various steps in
making compression joints are shown in Fig 4.7.
Maximum conductor length shall be made use of in
order to reduce the number of joints. All the joints
on the conductor shall be of compression type, in
accordance with the recommendations of the
manufacturer for which all necessary tools and
equipments like compressor, die sets of correct size
etc. shall be arranged.
The conductor surface shall be clean smooth and
without any projections, sharp points, cuts,
abrasions etc. Conductor joint shall be coated with
an approved mix of linseed oil and zinc chromate
immediately before final assembly as recommended by
suppliers. Surplus mix shall be removed after
assesbling. Vol.5 : Page #
The aluminum filler holes in the MSCJ should be used
to verify the centering of the joint. It should be
ensured that the filler holes are filled before
starting compression of the Aluminium sleeve. The
conductor joints shall be minimum 30 meters away from
any towers. No joints or splices is allowed in single
spans. Midspan joints shall not be used in any single
span crossings such as major power lines, major
rivers, railway lines etc. Compression type fitting
used shall be of self centering type or care should
be taken to mark the conductors to indicate when the
fitting is centered properly. During compression or
splicing operation, the conductor shall be handled in
such a manner as to prevent lateral or vertical
bearing against the dies.
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After pressing the joint, both the aluminum and steel
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sleeve shall have all corners rounded, burrs and
sharp edges removed and smoothened using smooth
files. Similar practice is used for pressing dead end
cone of the tension insulator hardware.
After making midspan joint, the joint is covered with
joint protector sleeves which is designed to pass
over the aerial roller grooves without damaging the
midspan compression joint. The paying out is
continued until the conductor reaches the puller
end in sufficient length to be connected to the
tension hardware. The conductor is held with come
along clamps on both tensioner and puller ends to
ground anchors. The pilot wire is disconnected and
paying out of next phase can be started or machines
shifted to next reach.
4.3.8 Rough sagging of conductor
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Before final sagging the conductor, it is rough
sagged to a tension slightly less than the final
tension. Since final sagging is done from one end of
the section, the conductor is initially attached to
the double tension string assembly on the other end.
For doing rough sagging, initially the double tension
string assembly is assembled with insulators and
hardware and hoisted to the cross arms/bridge as done
in the case of suspension towers. The dead end cones
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are compressed on both the sub conductor ends. The
conductor is held by comealong clamps at a distance
of 5 to 6 mtrs from the dead end cones and with the
help of a pulley connected to a ground anchor, the
conductor is pulled to slacken the free end of
conductor (sufficient length to be attached to the
hoisted insulator string assembly).
By holding the conductor with pulley, the dead end
cones are attached to the tension string. The pulley
is slowly released and the conductor will haul-up
itself to the top. The come along clamps and pulley
etc. are removed.
4.3.9 Final sagging of conductor
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The sagging of the conductor shall be done using
sagging winches. After being rough sagged the
conductor shall not be allowed to hang in the
stringing blocks for more than 96 hours before being
pulled to the specified sag.
The tensioning and sagging shall be done in
accordance with the approved stringing charts before
the conductors are finally attached to the towers
through the insulator strings. Only after the
conductor is rough sagged on the adjacent section,
final sagging can be done in the preceding section to
avoid overloading of towers. For doing the sagging
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operation, a span has to be selected in the section to
fix the sag board and check the sag.
In the event of using sag tension charts showing sags
in each of the actual spans and tension in each
section, usual practice is to place the sag boards in
the longest span of the section, and in a span where
the difference of elevation in the two suspension
points is minimum.
In case of referring the general sag tension charts
for spans with 5 mtr increment in length and 2 degree
centigrade raise of temperature, the equivalent span
has to be calculated for all the spans in the
section.
The following formula is used.
¦ L13 + L2
3
+...¦ Equivalent Span (L) = (sq. root of) ¦-------------¦ ¦ L1 + L 2 ¦
L1, L2 - Individual spans in a section
A span in the section is to be chosen which is equal
to the equivalent span with a maximum variation of
plus or minus 2.5 mtrs. The tension and sag required
are to be noted for the prevailing actual temperature
at the time of checking the sag. Sag board is to be
fixed to a tower on one side of the span by measuring
the sag length using steel taps from the cross arm
level after adjusting for vertical insulator and
other hardware lengths. On the other tower (sighting
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end), a thread is to be horizontally tied at the same
measured elevation from the cross arm.
The tension insulator strings are hoisted with all
hardware on the tower. The details of tension
fittings are shown in fig.4.8. The conductors are
held by come-along clamps and attached to separate
four sheave pulleys at sufficient distance of say 40
to 50 mtrs depending upon rough sag condition and
height of the tower. The other ends of the four
sheave pulleys are connected to the line side yoke
plate of the double tension string. The pulling
wires of the four sheave pulley are passed through a
set of single sheave pulleys along the body of the
tower to the ground level. The initial pulling is
done with the help of tractor/truck .Then the
pulling ropes are attached to hand winches mounted on
the legs of the tower or power winches duly
anchored. Wooden cross bars are tied to the body of
the four sheave pulley and held by ropes in a
horizontal position to avoid over turning of the
four sheave pulley and twisting of the pulling wires.
A view of final sagging is shown in fig.4.9.
The conductor is brought into final sag position with
the help of winches and the sag is checked by
sighting far end sag board from behind the near end
sag thread by matching elevation tangent of the
conductor curve. Sighting should be done keeping Vol.5 : Page #
sufficient distance from the sag line to avoid
parallax error.
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After reaching the final sag, the free end of the conductor
is picked up and pulled by rope and pulley
attachment along the line of the string. The
conductor is marked at the point where cutting is to
be done and dead end cone is to be pressed. The
free ends of the conductors are brought down and cut
near the marking and dead end cones are pressed. The
four sheave pulley is slightly tightened to
facilitate attaching the dead end cone to the tension
assembly. After fixing, the four sheave pulley is
slowly released, brought down and all clamps and
pulleys are removed.
4.3.10 Regulation :
Back to Contents Page
If the running blocks/aerial rollers which are used to
string conductor are not frictionless, it can cause
problems during sagging operation. If one or more of
the travellers become jammed, sagging can become very
difficult.
A running block swinging in the direction of the pull
can be an indication of a defective block. If
unforeseen sagging difficulties occur, the block
should be checked. Tensions applied to the conductor
to overcome sticky or jammed blocks can cause sudden,
abrupt movement of the conductor in the sag spans and
quickly cause loss of sag, particularly, if the
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conductor is already very close to final sag.
Care shall be taken to eliminate differential sags in
the sub-conductor as far as possible. However, sag
mismatching more than 40 mm shall not be allowed.
For checking the mismatch of the sub conductors with
horizontal, a theodolite shall be placed in the
alignment of the phase near the tower. The vertical
angle is raised to match the horizontal cross hair to
touch the tangent of the sub conductors. Mismatch can
be corrected by adjusting the sag using the sag
adjustment plates.
4.3.11 Clipping of conductors :
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The clipping of the conductor follows sagging
operation. This entails removing the conductors from
the rollers and placing them in suspension clamps
attached to the insulator string. Before taking
up clipping operation, the conductor is earthed
properly on suspension towers. The conductors are
held with hooks at 2 mtrs away from the aerial
roller on both sides. A wire rope is connected to
both the hooks passed through a pulley positioned on
the cross arm tip in series with a pull-lift/ratchet
lever hoist/four or two sheave pulley.
The centre of the aerial roller is marked on the
conductor. The conductor is raised by about 75 to 100
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mm and the aerial roller is removed and lowered by
rope and pulley. The suspension clamp and armoured
rods are fixed with neoprene rubber cushions centered
over the marking.
The suspension clamp is placed over the armored rods
and clamped with U bolts. The suspension clamp is
connected to the string and the lifting device is
released. The insulator string will hang freely with
the conductors suspended in the clamps. The
verticality of the string may be checked with plumb-
bob.
Care should be taken to prevent any damage to the
conductor while being lifted by hooks. Gunny bags or
rubber pads may be used around the conductor to
prevent damage to the outer strands.
4.3.12 Fixing of line spacers :
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Following the clipping operations for bundled
conductor lines, spacers are usually installed. This
is done by placing personnel on the conductors with
the use of a conductor cycle normally known as
spacer-cycle to ride from structure to structure.
Depending on the length of line to be spaced and the
equipment available, cycles may be hand powered
or diesel powered.
Care must be exercised to ensure that the concentrated
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load of the man, car and equipment does not increase
the sag sufficiently to cause hazards by obstructions
(spacers, repair sleeves, midspan joints etc.) over
which the cycle will pass.
The installation of the spacers on the conductor
varies with span length, the type and manufacture of
the spacer and is normally done in accordance with
the manufacturer's recommendations duly approved.
The spacer cycle is hoisted on the bundle at one
tension end. In case of engine powered cycles, the
spacer cycle is normally provided with travel meter,
with the help of which the spacers are fixed at re-
quired distances as per the placement chart. In case
of hand powered cycles, the personnel pulling the
cycle with rope measure the distances on ground and
placement is done on the top. A number of models of
spacers are being manufactured and the method of
installation varies with the design of the spacers.
After reaching the next suspension tower, the cycle
is transferred to the next span by crossing the
suspension clamp with the help of crossing ropes
provided in the cycle.
In case of spans crossing HT/LT lines, care should be
taken while drawing the spacer cycle with rope. Safe
electrical clearance should be maintained to the
spacer cycle and rope. For crossing the lines, the
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after crossing the line, keeping sufficient clearance
from the line. The person on the cycle can travel
himself to cross over the section above the power
line.
4.3.13 Installation of dampers :
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Vibration dampers/spacer dampers are normally placed
on the conductors immediately following clipping to
prevent any possible damage because of vibrations to
the conductors, which at critical tensions and wind
conditions can occur in a matter of hours.
In lines where spacer dampers are installed,
vibration dampers need not be installed. The number
of dampers and spacing are provided as per the
instructions of the manufacturer.
4.3.14 Jumpering
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The jumpers at the section/angle towers shall be
formed to parabolic shape to ensure minimum clearance
requirements. Pilot suspension insulator string shall
be used if found necessary (Generally where angle of
deviation is more than 45 degrees), to restrict the
jumper swings to the design values at both middle and
outer phases. Clearance between the conductors and
ground, jumpers and the tower steel work shall be
checked during erection and before commissioning the
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line.
While jumpering is made, a local earthing should be
made to avoid any static discharge that might occur
due to the voltage induced on the line by existing
power lines in the vicinity.
Care should be taken to leave jumpers for one angle
tower in a continuous stretch of 25 to 30 kms, so as
to prevent transmission of electric shock. These left
out jumpering can be taken up during final
inspections. The individual sections jumpered shall be
kept earthed and earth shall be removed only before
commissioning.
The jumpers in general are 10 to 15 mtrs in length.
Hence left over bits of conductor shall be used for
jumpering. For installation of jumpers, the distance
between the jumper pads of dead end cones is measured
by passing a rope in the shape of a jumper and by
checking vertical clearance from the cross arm end.
Conductor is cut after making adjustment in length
for the jumper cone dimension.
The inner and outer conductor of the bundled jumper
are of different lengths, which shall be measured
separately. This will ensure a horizontal plane of
the jumper bundle when installed. After cutting the
conductor, jumper cone is pressed using hydraulic
compressor. The conductors are laid out on the ground
parallelly and spacers are fixed as per the fixing Vol.5 : Page #
instructions. The jumper is hauled up from both ends
of the tension clamps and jumper cone is attached to
the connector of the dead end cone. Clearance to the
tower body shall be checked as per the drawing.
4.3.15 Paying out through angle towers :
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In order to reduce wastage of conductor, the
possibility of paying-out of conductor through
angle towers using TSE may be considered.
Here the running blocks or rollers are fixed to the
cross-arm peaks through sufficiently long steelropes
of 20 mm dia measuring maximum 30 cm. care may be
taken that the pulling is done slowly and smoothly
when the equalizer pulley passes the roller, so that
no jerks comes to the cross arm peak. Cross arm
stays may be provided as a precautionary measures.
If substantial line angles are involved, two running
blocks in tandem may be required to reduce the
bending radius of the conductor or load on each
running block or both. Where bundle conductor running
blocks are used at line angle more than 5°, it is
advisable to change to individual single conductor
running blocks after passage of the running board to
facilitate accurate sagging. It is desirable during
sagging for horizontal spacing of the sheaves to
match the final subconductor spacing to avoid
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subconductor sag mismatch.
However, if any noticeable damage is sustained to the
conductor, this procedure should be abandoned.
4.3.16 Transposition arrangement :
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In 400 KV S/C and D/C lines, the 3 phases are
transposed in equal lengths of 1/3rd distance of the
line to achieve equal mutual coupling between the
phases and earth.
Normally, C type towers without any angle of
deviation are placed at 1/3rd, 2/3rd and at the end of
the transmission line (about 2 to 3 spans before
the terminal gantry).If possible, transposition tower
should be placed at section tower where B type tower
with 0 degree is already proposed otherwise, to save
the cost. In lines where double circuit portions are
constructed in forest reaches, major river crossing
reaches etc. if it is possible, the transposition can
be done while changing over from double circuit to
single circuit without providing any extra
transposition tower.
The arrangement of transposition involves jumpering to
change the phases in the required position. The centre
phase and one of the side phases is transposed to the
other side of the tower by means of jumper attached
to a pilot insulator suspended from the cross arm
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tips. The 3rd phase is transposed from one side of
the tower to the opposite side of the tower on the
farther phase by jumpering through top of the tower
where a small line is strung between the earthwire
peaks with two single tension fittings with sag
adjustment turn buckle. Compression type T -
connectors are provided on the line conductors and
the jumpers are connected using compressed jumper
cones. Compressing of T connectors on the line
conductors can be done at the time of make up or
final sagging operation as per the drawing.
Compression of T-connectors after saging is completed
will be very difficult since either the line has
to be brought down or the compressor machine has to
be hoisted and joint made at line elevation.
Fig.4.10 is a view of 400 KV S/C transposition tower.
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4.4 Stringing over river crossing.
Back to Contents Page
In major river crossings having multi-span section
with suspension towers, there are special arrangements
and some precautions to be taken during stringing.
It is better to plan stringing activity during the
dry seasons of the year. In rivers where there is
water flow through out the year, extra precautions
have to be taken. The method of stringing in major
navigable rivers having flow of water through out the
year, is explained below. In case of navigable
rivers prior intimation should be given to the local
authorities and boat operators in the nearby areas.
Caution signals shall be raised with red flags about
1 km up and down streams of the alignment.
4.4.1 Earthwire
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Paying out of earthwire cannot be done length by
length as is normally done in ordinary sections. As
explained earlier, special drums having full length of
the sections are procured for stringing. Initially, a
polypropylene rope of say 1 km length is passed
through the section over the aerial rollers by
carrying the rope in boats. After paying out the
polypropylene rope the earthwire is attached from one
end of the section and pulled by the rope through the
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aerial rollers. The earthwire drums are mounted on
horizontal turn tables or rolling jacks which
shall be frictionless. After pulling for each span,
the rope may be passed to the next span manually and
pulling of earthwire may be continued. The T&P
required for sagging also will need longer pulling
wire of four sheave or two sheave pulleys as the
tower heights are very large.
4.4.2 Paying out of conductor
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In multispan reaches of major river crossings the
conductor has to be paid out using tension stringing
equipment. The pilot wire has to be initially paid
out from one end of the section as is done in the
case of earthwire by using polypropylene rope. The
total pilot wire reels required have to be kept at
one end of the section and joined with pilot wire
connectors after each length is pulled. Conductor
paying out can be done by normal stringing method. It
is better to procure conductor of larger length than
normally supplied, to avoid midspan joint of conductor
in the river crossing reaches. However, the conductor
reels should not be too heavy and cause difficulty in
handling and transporting.
In case the dead end towers used for the river
crossing reach are also of special type much taller
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than the normal towers, it is advisable to string
the river crossing reach upto the next angle tower
of normal size and do double side sagging at the
Anchor towers. Thus using of long stays which are
difficult in laying can be avoided. Also, long stays
are not reliable keeping in view the large bending
moment experienced by the tower
For long spans in river crossings, the sag is very
high. Care should be taken while checking the sag
with help of sag board so as not to give chance for
any error due to wind load on the conductor. It is
better to carry out the sagging operation in near
still wind condition. Sub conductor mismatch in
large spans shall be avoided completely at the time
of erection itself since differential creepage in the
conductors may cause large difference in the
conductor elevations. In spans exceeding 500 mtrs,
due to the large sag, pulling of spacer cycle
becomes very difficult in approaching the tower from
centre of the span. Also pulling from the ground may
not be possible due to flow of water. Under these
conditions, it is better to use powered cycles with
good braking arrangement.
All bolts & nuts of hardware shall be doubly checked
for tightness, provision of spring washers, cotter
pins etc. to avoid tower failure.
4.5 Stringing over power line crossings Vol.5 : Page #
Back to Contents Page
In the alignment of the Transmission line, many power
line crossings are encountered ranging from LT to
EHV. While crossing major power lines, due to
limitations of the tower spotting requirements and
reasons of economy, the minimum clearance of 6.10
mtrs is provided from the 400 KV line. Sagging has to
be very accurate and physical clearance from the
power line shall be checked after the sagging
operation.
While planning the stringing operation in reaches
where power line crossings are encountered advance
action should be taken to obtain line clear permit to
work from the utility operating the power line. The
line clear can be taken after paying out of pilot
wire, earthwire and conductor in sections which can
be joined after obtaining the shutdown.
In case of power lines upto 33 KV, it is easier and
economical to bring down the LT/HT conductors at two
or three poles. In case of lines of 132 KV and
above, bringing down the conductor is very difficult
and in many cases the utilities will not agree for
doing so. Any damages to the conductor or insulators
of the line to be brought down will cause a lot of
inconvenience and unnecessary outage of the line.
It is suggested to request utility to arrange as a
precautionary measure few hardware fittings and Vol.5 : Page #
insulator in order to replace them, if necessary. In
such cases, special cylindrical rollers fabricated
out of soft wood about 50 cms in length and 30 cms in
dia split in cross section with a groove at the
centre to accommodate the conductor of the line may
be used.
These rollers can be mounted on the conductor or
earthwire of the power line to be crossed and the
conductor to be strung can be drawn over these
rollers. Normally, crossings of major lines is done
in one or two spans only with dead end towers at
both ends and commonly with a special extension tower
of suspension type in the middle. Tension stringing
of these reaches will be very difficult and
unwarranted since the no. of spans is normally limited
to two only.
All the activities of paying out, sagging, placement
of line hardware & accessories shall be completed
during the shutdown period since it will be very
difficult to carry out operations without shutdown
afterwards. In spans using special extensions of 18
or 25 mtrs, the conductor slope is very high making
it very difficult for placement of bundle spacers
using the spacer cycle. Precautions should be taken
by holding a control rope from the spacer cycle to
the tower to avoid any accident.
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Chapter-5
Guidelines
______________________________________________________________________
CHAPTER FIVE
______________________________________________________________________
GUIDELINES
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GL-1 PRE-STRINGING CHECKS
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
Following preparations need to be made before taking up
stringing work.
1.1 Foundation checks
1.1.1 Backfilling of soil of foundation should be done
wherever required since back filled earth might have
settled down with the passage of time. Area should be
fairly levelled within four legs.
1.1.2 Revetment / Benching wherever required shall be comp-
leted so that there is no danger to foundation during
and after stringing work. However, if it is felt
that, non-completion of Revetment / Benching is not
going to harm foundation during and after stringing,
the same may be programmed and executed on later
date.
1.2 Tower checks
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1.2.1 The tower shall be checked by two supervisors starting
simultaneously from the bottom of the tower at two
diagonally opposite legs. The checking shall be
carried out towards the top of the tower and the
supervisors will come down checking through the
other opposite diagonal legs.
1.2.2 It shall be ensured that correct size of bolts/nuts
are used and fully tightened.
1.2.3 It shall also be ensured that all bolts/nuts have been
provided with spring washers.
1.2.4 A torque wrench may be used at random to ensure
sufficient tightness.
1.2.5 Any missing members shall be provided with correct
size member.
1.3 Way leave clearance
1.3.1 In order to maintain cordial relations with the field
owners for smooth completion of stringing, it is
desired that compensation of damage of crops during
foundation and tower erection is paid to the field
owners before taking up stringing work.
1.3.2 Also, wherever possible and if found necessary,
compensation of crop to be damaged during stringing
may be processed in advance for prompt payment.
1.3.3 Advance precautions should be taken to handle way
leave problem. Rough handling of the issue may spread
to nearby villages along the line resulting into total
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stopage of site activities.
1.4 Tree cutting
1.4.1 Immediately after completion of detailed survey,
issual of notices and valuation of trees by Revenue
Authorities should be taken up. Wherever necessary,
clearance from Forest Authorities may be taken for
tree cutting.
1.4.2 The tree cutting may be carried out alongwith
foundations so that the same is completed before
tower erection.
1.4.3 Any left over tree may be removed well in advance in
order to achieve smooth stringing and requisite
electrical clearance.
1.4.4 Tree compensation should be paid as promptly as
possible to gain confidence of field owners for
smooth completion of balance construction work.
1.5 Line material & drawings
1.5.1 It shall be ensured that all approved drawings of
line material and stringing charts with latest
revision are available at site to facilitate
stringing works. Preferably one set of drawing in
Bound Book shall be available at site with each gang.
1.5.2 All line material shall be available at site as per
requirement.
1.5.3 Though all the line materials are checked for any
defect before entering into stock Register yet it is
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necessary to keep constant watch on line material
during stringing for any other damage. It shall be
ensured that no defective line material is used at
any cost.
1.6 Tools and plants
1.6.1 All the tools and plants required for safe and
efficient stringing shall be available at site. A
list of necessary tools and plants is given at
Annexure-S/1.
1.6.2 All the tools and plants shall be tested as per
approved safety norms and relevant test certificates
shall be available. In addition to above, periodic
testing of tools and plants shall be carried out and
its safe working capacity shall be worked out and
recorded.
1.6.3 It shall be ensured that Tension stringing equipments
and other measuring instruments are properly
calibrated and relevant certificates are available.
1.7 Personal protective equipments
1.7.1 All the persons working on tower or
conductor/Earthwire shall wear safety helmet, safety
belt and safety shoes. Similarly all the persons
working on ground shall wear safety helmet and safety
shoes. List of personal protective equipments is given
at Annexure-S/1.
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1.7.2 Safety equipments shall be tested as per safety norms
and necessary test certificate shall be available.
Also, a periodic check shall be carried out to ensure
requisite strength.
1.8 Manpower
1.8.1 Manpower engaged for the purpose of stringing shall
be skilled and competent enough to ensure safe,
smooth and efficient stringing activity.
1.8.2 A list of necessary manpower required for stringing
is given at Annexure-S/2.
1.9 Misc
1.9.1 Shutdown of power line crossings shall be planned
well in advance. Shutdown should be obtained in
writing and lines are dismantled if required.
1.9.2 Similarly for Railway crossing, necessary block shall
be planned well in advance. Proper protection /
scaffolding shall be provided before taking up
stringing.
1.9.3 Road and Telephone line crossings shall also be
provided proper scaffolding and warning signals.
1.9.4 Tower vulnerable for one side load shall be guyed
properly both at waist and bridge level so as to
avoid any untoward incident.
1.9.5 Wireless communication (walky - talky ) sets shall be
in proper working condition.
1.9.6 It shall be ensured that tower footing resistance has
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been measured and found within permissible limit of
10 ohm.
1.9.7 It shall be verified that Drum schedules for
conductor and earthwire have been submitted and
approved well in advance. This is compulsory for
optimum use of conductor and earthwire to minimise
wastages.
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GUIDELINES
GL-2 PAYING OUT OF EARTH WIRE
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
2.1 Safety precautions
Safety shall be given utmost importance during
stringing. The following need to be ensured
2.1.1 Safe working conditions shall be provided at the
stringing site
2.1.2 All persons on tower/earthwire shall wear safety
helmet, safety belt and safety shoes and all the
persons on ground shall wear safety helmet and safety
shoes
2.1.3 Immediate Medical Care shall be provided to workmen
met with accident. First Aid Box shall be available
at stringing site.
2.1.4 Traveller ground shall be provided between Earthwire
drum and the section tower to avoid any potential
hazards.
2.1.5 Foolproof communication through walkie talkie shall
exist in order to avoid any danger to workmen or
public on ground while paying out.
2.2 Checking paying out process
2.2.1 General
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a) Relevant approved drawings as mentioned in para 1.5.1
shall be referred to.
b) It shall be made sure that paying out is carried out
as per approved drum schedule.
c) All the pulleys fixed on towers for paying out should
move freely to avoid any damage to earthwire or
pulley and to achieve correct final sagging.
d) One person on each tower shall be available with red
and green flags and whistle for supervision and
communication.
e) Walky-Talky sets shall be in good working condition
for smooth communication between pulling tractor and
unwinding of E/W drum.
f) Earthwire shall be checked constantly as it is
unwound from earthwire drum for any broken, damage
or loose strand. If any defect is noticed then
the defective portion has to be removed and mid
span joint provided. It may be mentioned here that
there is no repair sleeve for earthwire.
g) Necessary arrangement shall be made to avoid any
rubbing of earthwire against ground or hard surfaces
so that earthwire is not damaged.
2.2.2 Details of earthwire
Details of Manufacturer, Drum No., Length and
Location nos. between which earthwire is paid out,
shall be recorded in order to maintain traceability so
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that any problem encountered during operation and
maintenance can be properly investigated in case of
failure.
2.2.3 Details of M.S. Joint
a) M.S. Joint shall be provided strictly as per approved
drawings and technical specifications.
b) Following details of MS Joint shall be recorded.
i) Manufacturer's name and batch number
ii) Earthwire No.1 or 2 and Location nos. between
which MSJ is provided.
iii) Dimensions of M.S.Joint before and after
compression shall also be recorded and shall be
within permissible limits as per approved
drawings.
c) M.S.Joint shall be provided atleast 30 meters away
from tower.
d) There shall not be any M.S.Joint over Rly/River/Main
Road Crossing.
e) Not more than one M.S.Joint shall be provided in one
span for each earthwire.
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GUIDELINES
GL-3 PAYING OUT OF CONDUCTOR
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
3.1 Safety precaution
Safety shall be given utmost importance during
stringing. The following need to be ensured.
3.1.1. Safe working conditions shall be provided at the
stringing site
3.1.2 All persons on tower/conductor shall wear safety
helmet, safety belt and safety shoes and all the
persons on ground shall wear safety helmet and safety
shoes.
3.1.3 Immediate medical care shall be provided to workmen
met with accident. First Aid Box shall be available
at stringing site.
3.1.4 Traveller ground shall be provided between Tensioner/
Puller and section tower to avoid any potential
hazards.
3.1.5 Fool proof communication through walkie talkie shall
exist in order to avoid any danger to workmen or
public on ground.
3.2 Tensioner/puller placing
3.2.1 It shall be ensured that Tensioner and Puller are
placed on firm and levelled ground Vol.5 : Page #
3.2.2 It shall be confirmed that Tensioner/Puller are
firmly anchored with ground with wire rope of atleast
20 mm diameter in order to hold them in place.
3.2.3 It shall be verified that suitable earthing by copper
cable of cross section of atleast 64 mm² is provided
for both puller and Tensioner.
3.2.4 Slope of pilot wire/conductor between Tensioner/puller
and section tower shall be approximately three
horizontal to one vertical as far as possible. This
is essential to restrict the load on traveller
and section towers.
3.2.5 It is also necessary that horizontal angle of pilot
wire/conductor between Tensioner/Puller and section
tower shall be as minimum as possible in order to
avoid damages to pilot wire/conductor and sides of
grooves of bull wheels.
3.3 Conductor drum placing
3.3.1 It shall be ensured that there is enough distance
between tensioner and conductor drum so as to avoid
brid caging and breaking of conductor strands.
Generally a distance of 25 to 30 meters will serve
the purpose.
3.3.2 Horizontal angle of conductor as it approaches
tensioner should be small enough to avoid rubbing
of sides of grooves.
3.3.3 Horizontal angle of conductor as it leaves conductor
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drum should be small enough to avoid rubbing of
conductor on side flanges.
3.3.4 It shall be verified that braking device is
functioning properly for conductor drum to get desired
level of control during paying out operation.
3.4 Sequence of paying out
3.4.1 It shall be ensured that earthwire is already paid
out before taking up paying out of conductors.
3.4.2 It shall be checked that proper sequence of paying
out is maintained in order to avoid any clashing and
damage to conductors and to avoid any unbalancing of
loads on towers. For this purpose following sequence
shall be maintained.
a) In case of D/C line, sequence of paying out of
conductor shall be from top to downwards.
b) In case of S/C line, sequence of paying out of
conductor is that outer phases are completed
before taking up middle phase.
3.5 Insulator hoisting
3.5.1 Checking of Insulators
a) Insulators shall be completely cleaned with soft and
clean cloth.
b) It shall be verified that there is no crack or any
other damage to insulators.
c) It is very important to ensure that 'R' clips in
insulator caps are fixed properly. This is a security
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measure to avoid disconnection of insulator discs.
d) Necessary precautions shall be taken so that no
damage to insulators is caused during hoisting. In
case of damage, the same needs to be replaced.
e) Details of insulators (i.e. Type, Make, KN, & Batch
No.), No. of discs, Loc. No. and phase (R, Y or B )
are to be properly recorded.
3.5.2 Checking of Suspension Fitting
a) It shall be verified that necessary hardware fitting
as per approved drawings is provided for insulator
strings.
b) It shall be checked that there is no damage to any
component of hardware fittings.
c) It shall be verified that all nuts and bolts are
tightened properly.
d) It shall be made sure that all the necessary security
pins (split pins) are fixed properly as per approved
drawings.
e) Details of suspension fitting (Type, Make, Batch
No.), Loc. No. and phase (R,,Y or B) are to be
recorded.
3.6 Checking paying out process
3.6.1 General
a) Relevant approved drawings as mentioned in para 1.5.1
shall be referred to.
b) It shall be made sure that paying out is carried out
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as per approved drum schedule.
c) All the Travellers fixed on tower for paying out
should move freely to avoid any damage to conductor
or Traveller and to achieve correct final sagging.
d) One person on each tower shall be available with red
and green flags and whistle for supervision and
communication.
e) Walky-Talky sets shall be in good working condition
for smooth communication between Tensioner and
Puller.
f) Conductor shall be checked constantly as it is
unwound from Conductor drum for any broken, damage
or loose strand. If any major defect is noticed
then the defective portion has to be removed and mid
span joint provided. However if the defect is of
minor nature i.e. number of damaged strands is not
more than 1/6th of the total strands in outer
layer, a repair sleeve shall be provided.
g) Necessary arrangement shall be made to avoid any
rubbing of conductor against ground or hard surfaces
so that conductor is not damaged.
3.6.2 Details of conductor
Details of Manufacturer, Drum No., Length and
Location nos. between which conductor is paid out,
shall be recorded in order to maintain traceability so
that any problem encountered during operation and
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maintenance can be properly investigated in case of
failure.
3.6.3 Details of M.S. Joint
a) M.S. Joint shall be provided strictly as per approved
drawings and technical specification.
b) Following details of MS Joint shall be recorded
i) Manufacturer's name and batch number
ii) Conductor No.1 or 2, phase R,Y,B and Location nos.
between which MSJ is provided.
iii) Dimensions of MSJ before and after compression shall
also be recorded and shall be within permissible
limits as per approved drawings.
c) M.S.Joint shall be provided atleast 30 meters away
from tower.
d) There shall not be any M.S.Joint over Rly/River/Main
Road Crossing.
e) Not more than one M.S.Joint shall be provided in one
span for each conductor.
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GUIDELINES
GL-4 FINAL TENSIONING OF EARTHWIRE AND CONDUCTOR
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
4.1 General
4.1.1 All the approved stringing charts and other relevant
drawings shall be available at site before taking up
the final tensioning.
4.1.2 Final sagging in a particular section shall be done
only after verifying that conductor and earthwire are
already rough sagged in adjacent sections. This is
very important to avoid overloading of towers due to
one side load.
4.1.3 It shall be ensured that all safety precautions are
being taken as detailed in GL-2 & GL-3.
4.1.4 Final Tensioning and sagging shall be carried out in
a calm weather when rapid changes in temperatures are
not likely to occur.
4.2 Fixing of sag boards
4.2.1 Thermometer shall be installed on tower at the same
elevation as that of conductor and far enough above
the ground to avoid the effect of ground heat
radiation.
4.2.2 The atmospheric temperature shall be read from
thermometer just prior to final sagging. The Vol.5 : Page #
corresponding value of sags for earthwire and
conductor shall be noted from approved stringing
charts. Initial sag tension chart shall be referred
for conductor and Final-Sag-Tension chart shall be
referred for earthwire.
4.2.3(a) In case of earthwire sag length shall be measured by
steel tape from earthwire peak after adjusting for
length of suspension clamps. The sag board shall be
fixed on tower at one side of sagging span. On other
side of sagging span, a thread shall be tied on the
tower at the same elevation as that of sag board.
(b) In case of conductor, sag length shall be measured by
steel tape from cross arm after adjusting for length
of suspension insulators and hardware fittings. The
sag board shall be fixed on tower at one side of
sagging span. On other side of sagging span, a thread
shall be tied on the tower at the same elevation as
that of sag board.
4.2.4 Sag boards are to be fixed as per following
a) For a section having length upto 8 spans, the sag
boards shall be fixed in first and last span.
b) For a section having length more than 8 spans, the
sag boards shall be fixed in first, intermediate and
last span.
4.3 Final sagging of earthwire
4.3.1 Rough sagged earthwire shall be tightened further by
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winch machine fixed on tower till, the final sagging
position is achieved.
4.3.2 The final sag shall be checked by sighting far end
sag board from behind the near end sag thread by
matching elevation tangent of the earthwire.
Precautions shall be taken to avoid any parallax
error.
4.3.3 Marking of earthwire shall be done correctly after
adjusting for length of tension clamp as per
approved drawings.
4.3.4 The earthwire shall be cut at the marked point and
Tension clamp provided.
a) Following shall be checked in respect of Tension
clamp.
i) All the components of tension clamp are properly
fitted as per approved drawing.
ii) All Nuts and Bolts have been properly tightened
iii) None of the components of the clamp is damaged. In
case of any damage, the same shall be replaced by
good one.
iv) Split pin has been properly provided.
b) Following shall be recorded regarding tension clamp.
i) Earth wire No. and location No. between which it is
provided.
ii) Batch No., Make etc.
iii) Dimensions before and after compression.
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4.3.5 Sag shall again be checked after fixing tension clamp
in order to ensure that no error is introduced by
fixing tension clamp.
4.4 Final sagging of conductor
4.4.1 Rough sagged subconductors of one phase shall be
simultaneously tightened by winch machine fixed on
tower till the desired final sag is achieved.
4.4.2 The final sag shall be checked as mentioned in para
No. 4.3.2
4.4.3 Marking of conductor shall be done correctly after
adjusting length of Tension fittings.
4.4.4 The conductor shall be cut at the marked point and
Dead end joint provided.
a) Following shall be checked in respect of tension
fittings.
i) Insulators shall be checked as detailed in para
3.5.1
ii) Tension fittings shall be checked in accordance with
para 3.5.2
b) The following shall be recorded in respect of Tension
fittings.
i) Wire No., Phase and location of towers on which it is
provided.
ii) Batch No., Make etc.
iii) Dimension of Dead end joint before and after
compression. It shall be within permissible limit as
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per approved drawings.
4.4.5 Sag mismatching shall be checked by sighting through
the Teodolite placed on ground near the tower. Any
mismatch shall be corrected by using sag adjustment
plate in Tension fittings. It shall be verified that
sag mismatch is not more than permissible limit of 40
mm.
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GUIDELINES
GL-5 CLIPPING AND FIXING OF ACCESSORIES OF EARTHWIRE
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
5.1 Clipping and Checking of Suspension clamps
5.1.1 It shall be ensured that correct marking on earthwire
is done to fix suspension clamp. The suspension clamp
after fixing shall be in exact vertical position.
5.1.2 Following shall be verified in respect of suspension
clamp.
a) Suspension clamp is provided strictly as per approved
drawings.
b) All the components of suspension clamp are properly
fitted as per approved drawings.
c) All Nuts and Bolts have been properly tightened
d) None of the components of the clamp is damaged. In
case of any damage, the same shall be replaced by
good one.
e) Split pin has been properly provided.
5.1.3 Following shall be recorded for suspension clamps:
a) Earthwire No and location No. of tower in which
suspension clamp is provided .
b) Batch No., Make etc.
5.1.4 Sag shall be rechecked to ensure that no error is
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introduced after clipping operation.
5.2 Checking of vibration Dampers
5.2.1 Following checks shall be carried out for vibration
Dampers:
a) Vibration Dampers are provided as per approved
placement chart.
b) All Nuts and Bolts have been tightened properly
c) There is no damage to V.D.
5.2.2 Following shall be recorded:
a) Make, Batch No. etc.
b) Wire No., Loc. No. of Dampers provided.
5.3 Checking of Earthwire Jumpers
5.3.1 Following shall be checked:
a) Earthwire jumper is provided on all tension towers as
per approved drawings and technical specification.
b) All Nuts/Bolts have been properly tightened
c) Split pin provided properly
5.3.2 Dimensions of jumper cone before and after
compression shall be recorded. It shall be within
permissible limits.
5.4 Checking of Copper Bonds
5.4.1(a) It shall be ensured that one copper bond is provided
for each suspension and tension clamp as per approved
drawing.
b) It shall be verified that there is no damage to
copper Bond. Vol.5 : Page #
c) All the Nuts/Bolts are properly tightened
5.4.2 Following shall be recorded:
a) Make, Batch No. etc.
b) Wire No., Location No. of tower on which it is
provided.
Vol.5 : Page #
GUIDELINES
GL-6 CLIPPING AND FIXING OF CONDUCTOR ACCESSORIES
Back to Contents Page
NAME OF LINE ...... NAME OF CONTRACTOR ......
SECTION - LOC. NO....... TO LOC. NO.......
6.1 Conductor Clipping
6.1.1 Before taking up clipping, the conductor should be
earthed to avoid any electrical hazards.
6.1.2 Conductor shall be marked properly so that after
placing of suspension clamp, the insulator fitting
hangs in exact vertical position.
6.1.3 Following shall be checked in respect of suspension
clamps.
a) Armour rods have been properly provided as per
approved drawings.
b) All the other components of suspension clamps have
been properly provided as per approved drawings
c) None of the components of suspension clamp is
damaged. In case of any damage, the same needs to
be replaced.
d) All Nuts/Bolts have been properly tightened.
e) All the split pins have been provided.
6.1.4 Since, the suspension clamp is part of suspension
fittings, the details of clamp may be clubbed with
that of fitting as per para 3.5.2
Vol.5 : Page #
6.2 Fixing of Vibration Dampers
6.2.1 Following checks shall be carried out for vibration
Dampers:
(i) Vibration Dampers are provided as per approved
placement chart.
(ii) All Nuts and Bolts have been tightened properly
(iii) There is no damage to V.D.
6.2.2 Following shall be recorded:
(i) Make, Batch No. etc.
(ii) Wire No., Loc. No. of Dampers provided.
6.3 Fixing of Spacer
6.3.1 Spacers shall be provided as per approved placement
chart.
6.3.2 Necessary precautions shall be taken while crossing
any LT/HT line to avoid any electrical hazards by
accidental touching of ropes.
6.3.3 All components of spacer shall be properly fitted as
per approved drawing.
6.3.4 None of the components shall be damaged. In case of
any damage, the same shall be replaced by good one.
6.3.5 All Nuts/Bolts shall be properly tightened.
6.3.6 The following shall be recorded.
a) Make, Batch No. etc.
b) Details of span, phase, no. of spacers provided,
distance between spacers.
NOTE - In case spacer dampers are to be provided, the
Vol.5 : Page #
guide line for fixing of spacer as per para 6.3 shall
also be applicable for spacer dampers.
6.4 Fixing of Jumper and Jumper Spacer
6.4.1 Before taking up Jumpering work, necessary earthing
of conductor shall be provided to avoid any potential
hazards.
6.4.2 Length of Jumper shall be carefully selected such
that it is in parabolic shape so as to give live
metal clearance and Jumper drop as per approved
drawing. Length of jumpers of sub-conductors of a
bundle shall be properly co-ordinated so that jumper
spacers lie in horizontal position as far as
possible.
6.4.3 Jumper cone shall be compressed as per approved
drawings. Its dimension before and after compression
shall be recorded and shall be within permissible
limits. Since Jumper cone is part of Tension fitting,
the details of cone shall be clubbed with that of
fitting as per para 4.4.4
6.4.4 All nuts and bolts shall be properly tightened. This
is very essential to ensure tightness of jumpers to
avoid arcing and flashover which may result in damage
of tension fittings and undesirable tripping of line.
6.4.5 Jumper spacers shall be provided as per technical
specification and approved drawings.
Vol.5 : Page #
a) Following shall be checked.
i) All components have been properly provided.
ii) No component is damaged. In case of damage, the same
shall be replaced.
iii) All Nuts and Bolts have been properly tightened
b) Following shall be recorded for Jumper spacer
i) Make, Batch No.
ii) Loc. No., Phase, No. of spacer.
6.5 Pilot Fittings
Following shall be checked in respect of pilot
fittings.
a) Insulators shall be checked as detailed in para
3.5.1
b) Fittings shall be checked in accordance with para
3.5.2
6.6 Checking of Transposition Tower
6.6.1 Before taking up transposition job, the following
documents shall be available at site.
a) The approved phase sequence to be kept on both sides
of tower.
b) The approved drawing of transposition tower having
all the relevant details.
c) The approved drawings of various line material to be
employed for transposition arrangement.
6.6.2 It shall be ensured that jumpers provided for
different phases are as per approved drawing. The
Vol.5 : Page #
point of fixing of jumper on conductor and length of
jumper shall be strictly as per approved drawing. The
live metal clearance of different phases shall be
measured and recorded. The live metal clearance
shall be within permissible limit.
6.6.3 T- Clamp/Jumper Cone
a) T-Clamp and Jumper cone shall be provided as per
approved drawings.
b) Dimensions before and after compression shall be
recorded. It shall be within permissible limit.
c) All Nuts/Bolts shall be properly tightened
6.6.4 Pilot Fitting & Balancing Weight
a) Pilot Fittings
Following shall be checked in respect of pilot
fittings.
i) Insulators shall be checked as detailed in para
3.5.1
ii) Fittings shall be checked in accordance with para
3.5.2
b) Balancing Weight
i) It shall be ensured that Balancing weights have been
provided as per approved drawings.
ii) There shall be no damage to Balancing weight. In
case of damage, the same shall be replaced.
6.6.5 Single Tension Fitting
a) Following shall be checked in respect of tension
Vol.5 : Page #
fittings.
i) Insulators shall be checked as detailed in para
3.5.1
ii) Tension fittings shall be checked in accordance with
para 3.5.2 and 4.4.4 (b).
6.6.6 It shall be ensured that earth mast on earthwire
peaks of tower have been properly provided as per
approved drawing.
Vol.5 : Page #
Annexure - S/1
Back to Contents Page
POWERGRID CORPORATION OF INDIA LTD.(CONSTRUCTION MANAGEMENT)
LINE CONSTRUCTIONSTRINGING ACTIVITY
Tools and Plants required for StringingGang for Tension Stringing
1. TSE Sets. - 1 set
(Tensioner & Puller of 8 t/10 t Cap.)
2. Running Block for conductor. - 100 nos.
3. Running Block for earthwire. - 60 nos.
4. Head Board. - 2 nos.
5. Pilot wire each of 800 m length. - 10 nos.
6. Pilot wire joint. - 12 nos.
7. Grnd. roller for Tension/Manual
Stringing. - 30/100 nos.
8. Wire mesh pulling grip
(One end open of reqd. dia. for
conductor). - 6 nos.
9. Wire Mesh Pulling Grip
(One end open of reqd. dia. For
earthwire). - 2 nos.
10. Wire Mesh Pulling Grip
(Double end open of reqd. size
for conductor.) - 4 nos.
11. Articulated Joint.
Heavy duty (20 t). - 10 nos.
Vol.5 : Page #
Medium duty (10 t). - 10 nos.
Light duty (5 t). - 5 nos.
12. Drum mounting jack for conductor
drum of 10 t capacity. - 4 sets
13. Turn Table (5 t.capacity). - 2 nos.
14. Anchor Plate (1.5 m.x1.0 m. x8 mm) with
15 Nos. Anchor Pins (45 mm dia. And
850 mm long). - 10 sets
15. Hydraulic compressor Machine 100 T
capacity with die sets. - 5 nos.
16. Travelling Grnd. - 12 nos.
17. Dynamometer - 10 T. - 4 nos.
- 2 T. - 2 nos.
18. Pilot wire reel stand. - 4 nos.
19. Four sheave pulley with 9 mm dia.
& 300 m length wire rope. - 6 sets
20. Four sheave pulley with 12 mm dia.
and 300 m length wire rope. - 2 sets
21. Four sheave pulley with 12 mm dia.
and 150 m. length wire rope. - 4 sets
22. Equiliser pulley (10 T. capacity). - 16 nos.
23. Conductor Lifting tackle. - 4 sets
24. Winch - Motorised/Manual - 10 T
capacity. - 4 nos.
25. Comealong clamp for conductor
(Bolted type/Automatic). - 50/20 nos.
26. Comealong Clamp for Earthwire Vol.5 : Page #
(Bolted type/Automatic). - 15/10 nos.
27. Trifor (5 T. Capacity) - 6 nos.
28. Aerial Chair for conductor. - 6 nos.
29. Aerial Trolley. - 4 nos.
30. Turn Buckle - 10 T. - 16 nos.
- 3 T. - 6 nos.
31. Tension/Sag PlateFor Tensioning
Purpose). - 6 nos.
32. Sag Board. - 8 nos.
33. Marking Roller. - 4 nos.
34. Mismatch Roller. - 2 nos.
35. Joint Protector. - 6 nos.
36. Walkie Talkie Set. - 4 sets
37. Theodolite with stand. - 1 no.
38. Thermometer. - 3 no.
39. Survey Umbrella. - 1 nos.
40. Hydraulic Wire cutter. - 2 nos.
41. Binocular. - 3 nos.
42. Flag (Red and Green) - 30 nos.
43. Crow Bar (1.8 m Length). - 10 nos.
44. Nail Puller. - 6 nos.
45. Wire Rope.
(19 mm. dia.). - 1000 m.
(16 mm. dia.). - 150 m.
(14 mm. dia.). - 900 m.
46. Polypropylene rope.
(25 mm. dia.). - 500 m. Vol.5 : Page #
(19 mm. dia.). - 500 m.
47. D Shackle.
(190 mm Long). - 40 nos.
(150 mm Long). - 125 nos.
(100 mm Long). - 125 nos.
48. Bulldog Clamp 100 mm Long. - 35 nos.
49. Hammers, spanners,( Both Flat and
ring) round files, flat files,
screw drivers, cutting pliers,
Steel and Metallic Tapes, - As per reqmt.
Hecksaw frames and Blades,
Deadmen, Scaffolding,Slings, etc.
50. Tents, Buckets, water drums,
camping cots, tables, - As per reqmt.
chairs, petromax lamps etc.
51. Safety equipments:
i) Safety helmets - 200 nos.
ii) Safety belts - 40 nos.
iii) Safety shoes - 200 nos.
iv) First Aid Box - 5 nos.
Note: The quantity of safety equipment may be changed as per
manpower engaged.
Vol.5 : Page #
ANNEXURE - S/2
Back to Contents PagePOWERGRID CORPORATION OF INDIA LTD.
(CONSTRUCTION MANAGEMENT)LINE CONSTRUCTION
Man Power Requirement
For Stringing Gang
1. Manpower requirement and average output per gang is given
as under:-
Sl. No. Description of line Manpower Nos. Average output
KM per month
1. 132 KV S/C Line 85 30
2. 132 KV D/C Line 85 15
3. 220 KV S/C Line 110 30
4. 220 KV D/C Line 110 15
5. 400 KV S/C Line 200 15
6. 400 KV D/C Line 200 8
2. Breakup of Manpower is as follows :
400KV S/C 220KV S/C 132KV S/Cor D/C Line or D/C Line or D/C Line
i) Engineer. 2 Nos. 2 Nos. 1 No.
ii) Supervisors. 10 Nos. 6 Nos. 4 Nos.
iii) Skilled Manpower.
(a) Fitters. 30 Nos. 20 Nos. 15 Nos.
(b) TSE operators. 2 NOS. 2 Nos. 2 Nos.
(c) Mechanics. 4 Nos. 3 Nos. 2 Nos.
Vol.5 : Page #
(d) Carpenters. 2 Nos. 2 Nos. 1 No.
(e) Skilled workers for
misc. works. 110 Nos. 50 Nos. 40 Nos.
iv) Unskilled workers. 40 Nos. 25 Nos. 20 Nos.
Vol.5 : Page #
Vol.5 : Page #
Chapter-6
Check Format
______________________________________________________________________
CHAPTER SIX
______________________________________________________________________
CHECK FORMATBack to Contents Page
POWERGRID CORPORATION OF INDIA LIMITED(CONSTRUCTION MANAGEMENT)
LINE CONSTRUCTION
Check Format
NAME OF LINE...... NAME OF CONTRACTOR......
SECTION - LOC. NO....... To LOC. NO.......
----------------------------------------------------------------ITEM CHECKED RESULT OBSERVATION,
IF ANY----------------------------------------------------------------
(A) Pre-stringing checks:
1) Backfilling of soil and
revetment/Benching wherever Yes/No
required is done.
2) Towers are tightened
properly and all the mem- Yes/No
bers, Nut/Bolts are provided.
3) Trees in the corridor
removed to facilitate Yes/No
smooth stringing.
4) All Line materials, tes-
ted T & P, safety equipments Yes/No
Vol.5 : Page #
and relevant drawings are
available for stringing.
5) Shutdown of Powerline/
Railway block if required, Yes/No
is arranged.
6) Necessary Protection/
scaffolding/warning signals Yes/No
provided for Railway/Power
line/P&T line/Road Crossing.
7) Towers vulnerable for one
side load is guyed properly. Yes/No
8) Tower footing resistance is
within permissible limit of Yes/No
10 ohms.
Vol.5 : Page #
(B) Paying Out of Earthwire
1) Work is being carried
out with full safety meas- Yes/No
ures as per guide line.
2) Travelling grounds are
provided Yes/No
3) Paying out is carried out
as per approved drum schedule. Yes/No
4) All pulleys fixed on
towers for paying out are Yes/No
moving freely.
5) Effective communication
exists through walkie-
Talkie and through persons
on towers. Yes/No
6) Earthwire is being con-
stantly checked as it is un- Yes/No
wound. Damaged portion, if
any, is removed.
7) Necessary arrangement
have been provided to Yes/No
avoid rubbing of earthwire
against hard ground.
8) Necessary details of
Earthwire, M.S. Joints Yes/No
Vol.5 : Page #
recorded as per Ann-
CF-I & CF-II.
(C) Paying out of Conductor
1) Work is being carried
out with full safety meas- Yes/No
ures as per guide line.
2) Tensioner/puller are
properly placed, firmly Yes/No
anchored and earthed.
3) Conductor drums are
placed properly to avoid Yes/No
bird caging
4) Sequence of paying out
is such that to avoid un- Yes/No
balanceing of load on tower.
7) Details of insulators
and fitting are recorded as Yes/No
per Ann. CF-III & CF-IV.
8) Paying out is carried
out as per approved drum Yes/No
schedule.
9) Travellers fixed on
towers are moving freely. Yes/No
10) Effective communication
exists through walkie-talkie
and through persons stand- Yes/No
ing on towers for smooth Vol.5 : Page #
and safe paying out.
11) Conductor is checked
continuously as it is un-
wound from drum. Damaged Yes/No
portion, if any, is re-
moved/repaired.
12) Proper arrangements
made to avoid rubbing of Yes/No
conductor on ground/hard
surfaces.
13) Details of conductor
and M.S.J/repair sleeve is Yes/No
recorded as per Ann. CF-I
& CF-II.
(D) Final Sagging and Tensioning of Earthwire and Conductor
1) Sag board is fixed cor-
rectly after taking into ac- Yes/No
count length of suspension
clamp/fittings.
2) No. of sag boards fixed
in a section is as per tech- Yes/No
nical specification.
3) Sag is measured corre-
ctly at prevailing tempera- Yes/No
ture. Details recorded as
per Ann. CF-V.
4) Sag mismatch is within Vol.5 : Page #
permissible limits of 40mm Yes/No
as checked with Theodolite.
5) After measuring sag,
marking/cutting of Earth-
wire/ conductor is done Yes/No
correctly to fix tension
clamp/fittings)
6) Details of tension clamp/
fitting are recorded Yes/No
as per Ann. CF-VI, CF-III,
& CF-IV.
(E) Clipping of Earthwire and Conductor
1) For clipping, the mark-
ing is done correctly so Yes/No
that suspension clamp/
fitting hangs exactly
vertical.
2) Before clipping of con-
ductor, proper earthing is Yes/No
provided.
3) Following line material provided
as per specification. Details
recorded as shown below.
a) Suspension clamp of
Earthwire and conductor Yes/No
as per Ann.CF-IV & CF-VI.
b) Vibration Dampers for Vol.5 : Page #
Earthwire and Conductor as Yes/No
per Ann. CF-VII
c) Details of spacer/spacer
damper/jumper spacer Yes/No
recorded as per Ann. CF-VIII.
d) Jumpers for Earthwire/
Conductor as per Ann. CF-IV Yes/No
& CF-VI.
e) Pilot fitting, wherever
necessary as per Ann. CF- Yes/No
III & CF-IV.
4) Sag/Tension again mea-
sured after clipping and Yes/No
found o.k. Details recor-
ded as per Ann. CF-V.
5) Transposition done as
per specification. Details Yes/No
of line material recorded
properly.
6) All line materials pro-
vided are as per specifica-
tion and approved drawings. Yes/No
All necessary details recor-
ded for traceability.
7) Jumpers tightened prop-
erly. Live metal clearance Yes/No Vol.5 : Page #
are as per specification.
8) Minimum Ground Clearance,
Clearances over Power line/ Yes/No
Railway line/River Crossing
are as per specification.
Certificate: Stringing is completed in all respect.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
VERIFIED
SIGNATURE
NAME
DESIGN:E4/E5
DATE
APPROVED
SIGNATURE
NAME
DESIGN: E6/E7
DATE
Vol.5 : Page #
ANNEXURECF- I
Details of Earthwire/Conductor
1. Make
2. Batch No.
3. Quantity and Location
Sl.No.
DrumNo.
Lengthmarked on
Drum
Lengthpaid
Paid between
From
Loc. No.
To Loc.
No.
Phase Wire No.
4. There is no damage to Earthwire/conductor before or
during stringing.Strands are in perfect position.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURECF- II
Details of M.S. Joint for Earthwire/Conductor and Repair
Sleeve for Conductor
1. Make
2. Batch No.
3. Location
Sl.No.
Between Loc. No. Phase Wire No.
4. Dimension - Recorded as per Ann.CF-IX
5. M.S. Joint has been provided at least 30 meters away
from tower.
6. There is no M.S. Joint over Railway/River/Main road crossing
7. Not more than one M.S. Joint provided in one span for
each Earthwire/Conductor.
8. Repair sleeve shall be used if number of damaged strands
is not more than 1/6th of the total strands in the outer
layer. If damage is more, then the damaged portion shall
be removed and M.S. Joint provided.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
ANNEXURE
CF - III
Records of Insulators
1. Type - Glass/Porcelain, Suspension/Tension/Pilot2. Make -
Vol.5 : Page #
3. Batch No. -4. Electro Mechanical Strength -5. Quantity and Location -
Sl.No.
Loc. No. Qty. asper drg.
Qty. in CKT-I Qty. in CKT-II
Phases PhasesR Y B R Y B
Remarks
6. Insulators are completely cleaned with soft cloth. Glazing
is proper. There is no crack, scratch or white spot on its
surface.
7. `R' Clips in Insulators are fitted properly.
8. While Hoisting, no damage caused to insulators.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURECF - IV
Details of Hardware Fitting
1. Make
2. Batch No.
3. Type of fitting - I/V, Single/Double, Suspension/Tension.
4. Quantity and Location.
Sl.
No.
Loc. No. No. of fittingsPhases
R Y B
Remarks
5. All Nuts/Bolts properly tightened
6. All components of fittings have been provided as per
approved drawings. Dimensions and galvanizing are O.K.
Fitting is cleaned and there is no damage to any component.
7. All split pins properly provided.
8. In case of Tension fittings, Dimensions before and
after compression recorded as per Ann.CF-IX
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURECF - V
Sag Measurement for Earthwire and Conductor
1. Sag board fixed between Loc. No......... and ....
2. Temperature ........°C
3. Measurement of Sag/Tension.
Item Phase/Wire No. As per Sag/Tension Chart Actual
Sag
Tension
4. During paying out/ rough sagging, tension in
conductor / Earth Wire was as per technical specifications.
5. For final sagging, initial stringing chart for conductor
and final stringing chart for Earth Wire are used.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
ANNEXURECF - VI
Suspension/Tension Clamps for Earthwire
1. Make
2. Batch No.
3. Quantity & Location No.
Sl. No. Wire No. Loc. No. Remarks
4. All components of clamps have been provided as per
Vol.5 : Page #
approved drawings. Dimensions and galvanizing are O.K.
Clamp is cleaned and there is no damage to any component.
5. All Nuts & Bolts have been properly tightened.
6. Split pins have been properly fixed.
7. In case of Tension clamp, Dimensions before and after
compression recorded as per Ann.CF-IX
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURECF - VII
Records of V.D. for Earthwire/Conductor
1. Make
2. Batch No.
3. Quantity & Location
Sl.
No.
Fixed on
Loc. No.
Fixed towards
Loc. No.
Phase/wire No. No. of V.D.
4. All components of V.D.have been provided as per approved
drawings. Dimensions and galvanizing are O.K. V.D. is
cleaned and there is no damage to any component.
5. Nuts/Bolts tightened properly.
6. V.D. fixed as per approved placement chart.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURECF - VIII
Records of Line spacer/spacer Damper/Jumper spacer
1. Make
2. Batch No.
3. Quantity & Location
Sl. No. Span/Loc. No. Phase No. of Spacer
4. All components of spacer have been provided as per
approved drawings. Dimensions and galvanizing are O.K.
Spacer is cleaned and there is no damage to any component.
5. Nuts/Bolts tightened properly.
6. Spacer/spacer damper fixed as per approved placement chart.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
ANNEXURE
CF - IX
Dimensions for M.S. Joints/tension sets for earthwire and conductor.
i) Type of joint ACSR (Mid span jt./dead end jt./jumper cone/)/E/W (Mid span jt./ dead end jt./jumper cone)/ACSR Repair sleeve/T-Clamp.
ii) Locn. No. ... ..... ..... ..... ..... iii) Span Loc. No. ..... to .. .. .. .. .. iv) Apprd. drg. Nos......................v) Details of dimensions
Steel portion Aluminium portion
As per drg. Actual As per drg. ActualBef. Comp. Aft. Comp. Aft. Comp. Bef. Comp. Aft. Comp. Aft. Comp.
Length Outerdia
Length C-C F-F Length C-C F-F Length Outerdia
Length C-C F-F Length C-C F-F
C-C : Corner to corner distance.
F-F : Face to face distance.
Vol.5 : Page #
vi) Bores in the sleeves are perfectly clean.
vii) The following may be checked as per approved drawing:
a) Marking and cutting.
b) Correct sizes of dies
c) Centering & fixing of sleeves.
d) Fixing of all the components i.e. Aluminium end
pipes, hole plugs etc.
e) Compression of sleeves at specified pressure.
f) Application of filler paste (Zinc chromate).
viii) All the sharp edges have been filed after compression.
ix) There is no crack, bend or any damage to joint
after compression.
FOR CONTRACTOR FOR POWERGRID
SIGNATURE SIGNATURE
NAME NAME
DESIGNATION DESIGNATION : E1/E2/E3
DATE DATE
Vol.5 : Page #
Vol.5 : Page #
Bibliography
______________________________________________________________________
BIBLIOGRAPHY______________________________________________________________________
(1) "Transmission line structures" by S.S. Murthy and A.R.
SanthaKumar.
(2) "Manual on Transmission Line Towers" - CBI&P - Technical
Report No.9.
(3) "Workshop on transmission line"-CBI&P- Vadodara (29th
Nov.- 2nd Dec.,94).
(4) "Symposium on Design & Protection of 400 kV Transmission
Lines" - CBI&P - Publication No.131 .
(5) "Overhead line Practice" by John Mccombe.
(6) "Guide to the installation of overhead transmission line
conductors" - IEEE Std. -524 - 1992.
(7) "Code of practice for Design, installation and
maintenance of overhead power lines"-IS:5613:1989.
(8) "Transmission line construction"-Electricity
Generating Authority, Thailand - Specification No.C-
2, Rev. 6 .
(9) "Technical Specification Vol.III" - Power Grid
Corporation of India Ltd.
(10) "Accident Report on Tower failure in NR-I"
(April,95)- Power Grid Corporation of India
Ltd.
(11) "List of checks for stringing" prepared by WR
(July,94)- Power Grid Corporation of India Ltd.
(12) "Construction Manual,Part-II, Transmission Line
Construction, Vol.-III, Section-III: Stringing" SRTS.
- Power Grid Corporation of India Ltd.
(13) Indian Electricity rules 1956.
(14) Indian Electricity Act, 1910.
Vol.5 : Page #
_____________________________________________________________________
_
RESUMES______________________________________________________________________
OUR TEAM
(1) Sh. V.C. Agarwal, AGM, is B.E. (Civil) and M.E. (Hons.)
in ‘Soil Mech. and Fndns. Engg.’ From Univ. of Roorkee,
Roorkee.
He has 28 yrs. of vast experience in Construction,
Planning and Monitoring of large Transmission Projects.
(2) Sh. D.K. Valecha, Sr. Manager, is B.Sc. Engg.
(Electrical) from Reg. Engg. College, Kurukshetra.
He has 17 yrs. of varied experience in Planning &
Monitoring, Construction, Operation & Maintenance of
Transmission Lines and Substations.
(3) Sh. J.K. Parihar, Manager, is B.E. Elect. (Hons.) from
Univ. of Jodhpur, Jodhpur.
He has 14 yrs. of varied experience in Planning &
Monitoring, Construction, Operation & Maintenance of
Transmission Lines and Substations.
(4) Sh. R. Nagpal, Manager, is B.E. Elect. (Hons.) from
Punjab Engg. College Chandigarh and MBA from Indira
Gandhi National Open Univ., New Delhi.
He has 12 yrs. of varied experience in Planning &
Monitoring, Construction, Operation & Maintenance of
Transmission Lines and Substations.
(5) Sh. N.K. Rai, Dy. Manager, is B.Sc. Engg. (Mech.) from
Birla Institute of Technology, Mesra, Ranchi.
He has 19 yrs. of varied experience including 8 yrs. in
Indian Army in Stores Management, 11 yrs. in Power Sector
in Planning, Monitoring and Contracts Deptt. at Corporate
Center.
Vol.5 : Page #
(6) Sh. B.K. Jana, Dy. Manager, is B.E. (Civil) from Regional
Engineering College Durgapur and M.Tech. in Applied
Mechanics from I.I.T. Delhi.
He has 14 yrs. of varied experience in Design, Planning &
Coordination of Sub-station works, TL Fndns., Pile Fndns.
& other special heavy Foundations.
(7) Sh. S.K. Niranjan, Engineer is B.Tech. (Civil) from
H.B.T.I., Kanpur (U.P.).
He has 7 yrs. of varied experience in design of
underground structures (Power Tunnels and Shafts) of
Hydro-Electric projects.
Vol.5 : Page #
CONSTRUCTION MANAGEMENT DEPTT.
Vol.5 : Page #
User’s ManualOf
Construction
Transmission Line(Part-1)
Sub-Station(Part-2)
General Support(Part-3)
Vol. 1Line Survey
Vol. 3Soil
Investigation &Foundation
Vol. 2Env. Mgmt.
Vol. 4Tower Erection
Vol. 1Land &Infrastr.
Vol. 3Switchyard
Ercn.
Vol. 2Civil
Construction
Vol. 4Ercn. Of TF,
SR & CB
Vol. 1MB
(Procedures& G. Lines)
Vol. 3Contracts
Mgmt.
Vol. 4Budget
& Finance
Vol.5 : Page #
Vol. 5Stringing
Vol. 5Aux. Pkgs.
(Elect.)
Vol. 5Labour
Regulations