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IS 5613 ( Part 3/Set 2 ) : 1988

Indian Standard

( Reaffirmed 2004 )

CODE OF PRACTICE FOR DESIGN, INSTALLATION AND MAINTENANCE OF OVERHEAD POWER LINESPART 3 Section 2 400 kV LINES and Maintenance Installation

UDC

621'315'17

@ BIS 1990

BUREAUMANAK

OFBHAVAN,

INDIAN

STANDARDSZAFAR MARO

9 BAHADUR SHAH NEW DELHI 110002

Janwy

1990

Price Group 8

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Conductors

and Accessories for Overhead Lines Sectional Committee, ETDC 60

FOREWORD This Indian Standard ( Part 3/Set 2 ) was adopted by the Bureau of Indian Standards on 23 March 1989, after the draft finalized by the Conductors and Accessories for Overhead Lines Sectional Committee hed been approved by the Electrotechnical Division Council. The present strategy for development of power hasnecessitated a rapid development of extensive EHV network covering the whole country. After successful introduction of 220 kV system in the country, 400 fV hasbeen adopted as the next higher system voltage after detailed techno-economic studies. For development of 400 kV network, this code provides, in addition to specifying the good practices for EHV lines, gives the detailed requirements with respect to 400 kV lines in particular.

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IS 5613 _(Part 3/Z&c 2 ) : 1989

Indian Standard

CODE OF PRACTICE FOR DESIGN, INSTALLATION AND MAINTENANCE OF OVERHEAD POWER LINESPART Section 2 3 400 kV LINES Installation and Maintenance

1 SCOPE 1.1 This code ( Part S/Set 2 ) covers installation and maintenance of 400 kV transmission lines. 2 REFERENCES 2.1 The Indian Standards listed in Annex Aare necessary adjuncts to this standard. 3 TERMINOLOGY 3.1 For the purpose of this code, the definitions given in IS 1885 ( Part 30 ) : 1971 and the Indian Electricity Rules, 1956 shall apply. 4 EXCHANGE OF INFORMATION 4.1 General A properdesign of transmission line and its supporting structures, insulators, conductors, etc, should be finalized on the basis of relavant Indian Standards. Detailedspecifications shall be prepared for individual items before~ordering the materials. 4.2 Transport Limitations Information about transport limitation particularly for line materials should be obtained from rail road or navigation authorities where required. This may involve procurement of special trailers or alternatively restricts the size and weight of the package in uneven terrain where head-loading is more often resorted to. 4.3 Terrain and Weather Conditions Informationon this is necessary in order to procure right type of installation tools and material handling equipments. 4.4 Right-of-Way (ROW ) and Access Requirments Having decided on the choice of route ( see 4 of Section 1 of this standard ), it is

necessary to inspect right-of-way before starting any construction work on theline. Information on vegetation 1

should be obtained along with a true assessment of problems facing procurement of right-of-way and way leaves for access, and compensation required to be paid.4.4.1 Compensation to the Owners Compensations to the owners for damage of crops, fruit trees and other vegetation, if required, should be evaluated with the help of the Revenue Authorities and paid accordingly. 4.5 Local Laws The~information about the local laws should be obtained in advance in order that there is noinfringement of prevailing local laws and to ensure smooth installation, operation and maintenance work. 5 GENERAL REQUIREMENTS 5.1 Materials and Equipment Allmaterials, fittings, etc, used in the installation and also the construction tools and equipment shall conform to the relevant Indian Standards wherever they ex

ist. In cases where there is no Indian Standard available, the items shall conform to the specifications mutually agreed between the purchaser and the manufacturer. 5.2 Compliance with Indian Electricity Rules and Other Authorities Regulations All overhead lines shall comply with the requirements of the Indian Electricity Act and Rules made thereunder and the regulations or specifications as laiddown by Railway Authorities, Post and Telegraphs Department, Roadway, Navigationor Aviation Authorities, Local Governing Bodies, Defence Authorities, Power andTelecommunications Co-ordination Committee, Forest Authorities and Oil & Gas Authorities, wherever applicable. Ralevant matters requiring attention of such authorities should be referred to them before planning the layout, installation andduring construction work. Such refenences, however, be

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IS 5613 ( Part 3/Set 2 ) : 1989 made by the owner of the installations and within appropriate time so as to ensure smooth progress. 5.3 The transmission line installation shall be carried out by trained and experienced personnel and supervised by technically qualified persons competent to undertake such work. 5.4 Scopeof Work Installation of overhead line includes waIk-over survey laying out theline ( route alignment ); detailed and check survey; clearing the work site andline route; making access roads; civil construction work of foundations, etc, erection of line; all connected material transport and handling till the line is ready for use; testing and commissioning or taking over. 6 SURVEY 6.1 Walk-Over Survey Before starting the detailed survey a walk-over survey of the line shall be made. The various feasible routes shall be ascertained and marked on the toposheet. 6.2 Route-Aligpment Map On completion of walk-over survey, a route-alignment map shall be prepared to a scale of 1: 50 000. All the topographical detailsincluding all railway lines, rivers, canaIs and important roads, power and telecommunication lines, oil and gas pipe lines, etc, up to 8 kms on either side of the-route of the line shall be drawn to the scale with longitude and latitude properly marked. Route near the towers or for railway line crossings or for certainstretches where the proposed lint route runs parallel to existing power/telephone lines, shall be drawn to the scale of I : 20 000, if required by the concerned authorities for containing necessary clearances. Jf considered necessary, a key map to a scale of I : 200 000 may be prepared showing the main sections of theline in addition to the above. 6.2.1 For convenient handling in the field, themaps should be made on sheets of ~3OOx I 190 mm, with 3~cm overlap shown on thesubsequent sheets. 6.3 Clearing Right-of-Way ( ROW ) and Access Roads The trees

essentially required to be removed for carrying out detailed survey be cleared,followed by complete clearing of ROW based on the actuaI route adopted. The clearing should be carried out both in the legal and physical sense. If any compensation has to be made on crops, it shall be accounted for the period till the installation work is to be over according to programme. 6.3.1 Clearing may be done in accordance with Fig. 1.

MAXIM&i

SWING

'

MINIMUM ELECTRICAL CLEARANCE 3

NOTE -

Portion of tree falling within clearance zone to be lopped or trimmed. LINE CLEARANCE ( RIGHT-OF-WAY ) REQUIREMENTS 2

FIG. 1

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IS :5613 ( Part. 3/Set, 2 ) : 1989 6.3.2 Taking into considera.tion the theoretical requirement of right-of-way .and transport requirements of maintenance, thefollowing right-of-way width for 400 kV lines are recommended: For single circuit line For double circuit line 3 50 m ( under consideration ) All topographicaldetails, permanent features such as road buildings, etc, w.ithin the rightof-wayshall be marked on the profile plane. 6.4.1 From the field book entries, the ruute. plan and level profile, commonly referred to as `survey chart' shall be plotted and prepared to the scales of 1 = 2 000 horizontal and 1 = 200 vertical on1 mm/5 mm/l cm square papers or formed tracing graph papers made for the purpose. The entire survey work shall be cross-checked with respect to the Standard Bench Marks. 6.4.2 If the difference in level is very ,high, the chart may be broken up according to requirments. A 1 cm overlap shall be shown on each following section and on each following sheet. The chart shall progress from left to right.For convenience in handling the sheet size may be limited to 420 x 1 190 mm or590 x 1 190 mm depending on whether profile is for plains or hills respectively.Each section shall be started on a new sheet. 6.4.3 Bearing strength, density and angle of repose of the soil shall also be determined in accordance with the standard test methods at the time of detailed survey for different type of terrain through which line traverses, 6.5 Sag Template and Tower Spotting A typical sag template is-shown in Fig. 2 and the method of its preparation and applicationfor tower spotting is given in Annex B.

6.3.3 While routing the transmission line, care shall be taken to avoid restricted areas such as civil and military airfields, coal bearing areas on quarry site

s, tea, tobacco, saffron field and any other tmportant plantation scheme, etc. Special care shall be taken to avoid routing the line through protected/reservedforest areas. If avoidance~of the forest stretches is not possible, the proposals, in the prescribed format as required by state/central forest authority, for obtaining the requisite clearance from the forest authority, shall be submitted by the owner of the installation. 6.4 Detailed Survey Detailed survey shall be conducted on the approved alignment. The choice of the method of survey, namely: theodolite or aerial survey considered, convement, shall be left to the surveyingparty. In hilly region, level of ground at a suitable distance below the outerconductor on either side from the centre line is also to be noted and marked inprofile so as to ensure required ground clearance underneath conductor and sideclearances in swung conditions of conductor.

1 represents cold template or uplift curve represents hot template or maximum sag curve 3 represents ground clearance curve2 4 represents support foot curve IMRT Central Line represents Right Offset Level IMLT Central Line represents Left Offset Level

FIG. 2

SAG TEMPLATE 3

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' IS 5613 ( Part 3/Set 2 ) : 1989 6.5.1 While locating the towers on survey charts, the following shall be borne in mind: the same voltage or Iower voltage, suspension/ tension tower with suitable extensions shall be used ( Refer Table 1 );Telecommunication Iine crossing

-a) Maximum length of a `section' shall not exceed5 km.

b) The intermediate

spans shall be as near as possible the normal design span. In case an individualspan becomes too short on account of undulations in ground profile, one or moreline supports of the section may be extended by inserting standard body extension designed for the purpose according to technical specifications to bring the intermediate span as near as possible to the design span; force on suspension tower under normal working condition, and the suspension towers shall support the minimum weight span as provided in the designs. In case uplift is unavoidable, itwill be examined if the same may be overcome by adding standard body extensionsto the towers, failing which tension towers designed for the purpose shall be employed at such positions; means of tower capacity the purchaser;Road crossing.

d There shall not be any upward

The angle of crossing shall preferably be 90". However, deviation to the extentof 30" may be permitted under exceptionally difficult situations. When the angleof crossing is below -6O", the matter shall be referred to the authority inchage of the telecommunication system. Also, in the crossing span, power line supports shall be as near the telecommunication line as possible, to obtain increasedvertical clearance between the wires; and Requisite clearance to foreign objectsshall be maintained. 6.6 Chesk Survey This will be conducted to make a check ondetailed survey and to locate and peg marks the tower positions on ground conforming to the survey charts. In the-process it is necessary to have the pit centres marked according to the excavation marking charts. The levels, up or down, ofeach pit centre with respect to the centre of the tower location shall be notedand recorded for determining the amount of benching or earthwork required to meet design requirements of the~foundation. 6.6.1 If the levels of the pit centres

be in sharp contrast with the level of the tower centre ( say beyond a slope of1 : 4 ), suitable `leg extensions' may be deployed as required. 6.6.2 For the sake of reference,the pits of a tower shall be designated as shown in Fig. 3. 6.7Tower Schedule A tower schedule shall be prepared for planning of materials. The proforma shall be made on a convenient sheet size of 280 x 508 mm. Tower schedule shall further be checked by means of the tower capacity charts approved by the purchaser. If the limits are exceeded anywhere, the spotting should be relocated by trials. 6.7.1 Along with the tower schedules, a line schedule should alsobe prepared which should cover in detail the total quantity of all line materials required and the quantity in which these are required at various points on the line. 7 MATERIAL TRANSPORT 7.1 All material transport shall be undertaken in vehicles suitable_for the purpose and free from the effects of any chemica1 substances. Tower members shall be loaded and transported in such a manner that these

are not bent intransit and sharp-hent members are not opened up or damaged.4

d) Tower spotting shall be tfurther checked bycharts

approved by

4

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At all important crossings, the towers shall be fitted with normal suspension ortension insulator strings depending on the type of towers but the ground clearance at the roads under maximum temperature and in still air shall be such that even with conductor bundle broken in adjacent span, the ground clearance of the conductor from the road surface shall not be less than 8'84 metres. At all national highways tension towers shall be used. The crossing span, however, shall notexceed 25 metres in any case;Railway crossings

For railway crossings, towers shall be of tension type and railway crossings construction shall conform to the regulations laid down by Railway Authorities;'

g)

River crossing

In case of major river crossings in planes, tower shall be of suspension type using double suspension strings and the anchor towers on either side of the main river crossing shall be dead end type. Clearance required by navigad tion authority shall be provided. For nonnavigable rivers clearance shall be reckoned with respect to highest flood level (HFL);

h) Power

line crossings

Where a line is to cross over another line of

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IS 5613 ( Part 3/Set 2 ) : 1989

REdEIL'ING...END t NAME OF SUBSTATION

)

4 LL

SENDING

(NAME

OF

(FEEDING) END SUBSTATION)

1 represents leg or pit No. 1 A represents near side (NS) transverse face 2 represents leg or pit No. 2 B represents near side (NS) longitudinal face 3 represents leg or pit No. 3 C represents far side (FS) transverse face 4 represents legor pit No. 4 D represents far side (FS) longitudinal face NOTES 1 Danger and number plates are located on face `A' 2 Leg 1 represents the leg with step bolts and anti-climb device gate, if any. If two legs with step bolts are required, thenext is No. 3 leg. FIG. 3DESIGNATION OF TOWER LEGS, FOOTINGSAND

FACES

Conductor and earthwire drums shall be handled carefully, so that the drums-andtheir contents are not damaged. 8 FOUNDATION 8.1 The construction of tower foundations be in accordance with IS 4091 : 1979. 8.1.1 Pit Marking Pit marking shallbe carried out according to tower schedule chart. The pit size in the case of open cut foundation shall be determined after allowing a margin of 150 mm all round. No margin is5

necessary inthe case of undercut foundations. The depth of the excavation at thepit centre shall be measured with reference to the tower centre level. 8.1.2 Sh

oring and Struttinp

shall

Shoring and strutting shall be done keeping in view the requirements given in IS3764 : 1966. In pits excavated in sandy soil or water bearing strata and wherethere is every likelihood of pits collapsing, shoring and strutting shall be made out oftimber planks or steel frames of adequate to suit the requirements. strength

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IS 5613f Part 3jSec 2 ) : 1989 8.1.3 Dewatering

The guidelines for dewatering during construction specified in IS 9759 : 1981 shall be kept in view. Dewatering shall be carried out manually by mechanical pumps or power driven pumps to facilitate excavation and casting of foundation. Thepums shall be suitable for handling mud water. The pits shall also be kept dewatered till 24 hours of concreting-the foundations. Dewatering is not necessary incase-of bored foundations below water table. These are stabilized by drilling muds and concreted by displacing the drilling mud. 8.1.4 Excavationsin Rock

centre punch or chisel markings on the ffanges and heel at the centre line positions of standard height towers as well as heights extended with standard body extensions. The plumb bob shall be dropped from these reference points which shallbe pre marked at the shops. The same template shall preferably be suitable forsetting stub positions for various tower heights. In case of hill side extension, a section of tower body may be used as template. For maintaining accuracy of setting, squaring and the slope, the plan diagonals and bracket pieces shall be fitted withthe template. 10.2 Assembly and Check

The provisions given in IS 4081 : 1986 shall be followed. For excavations in hard rock, blasting can be resorted to. Reference shall be made to statutory rulesfor blasting and use of explosives for this purpose. No blasting is permitted near permanent work or dwellings. Blasting shall be so made that pits are as near

to the designed dimensions as practicable. Jack hammers can also be used in theexcavation work. 8.1.5 All excavated material `shall be dumped at least 1 to 2 metre away from the pits, preferably in diagonal directions, keeping the space along the centre lines free for foundation work. Care shall be taken that no moving vehicles or heavy equip ment are drawn too near the excavated pits. 9 CLASSIFICATION OF SOIL

Assembly shall be made on adjustable screw jacks resting over compact ground. Initial levels shall Abemade with an accurate long bubble spirit level and template shall be centred properly bringing the side and diagonal measurements equal according to design drawing. Levels and alignment shall once again be checked after pouring slab/ pyramid concrete and before pouring chimney concrete and adjusted for differences, if any. 10.2.1 The allowable tolerances on template setting s

hall be as given in Annex C. 10.2.2 In case due to collapsed pits the template may not be fitted on jacks, the same shall be assembled with stubs resting over 1: 2 : 4 plain cement concrete blocks in comparatively green condition cast at the site with a 300 or 450 mm square base and a depth equal to the designed concrete cover under stab. The sides of the blocks shall be rough cast while the topshall be smooth for this purpose these may be cast in wetted pits made in ground. These blocks shall remain in position and shall form integral part of the foundation concrete. The templates should remain in position far not less than 24 hours and it should not be removed before back-filling is done. 11 CONCRETE 11.1 Type For reasons of-economy and progress it is normal practice to use coarse andfine agreegates available along with line route and/or nearest locations to theroute. A such, it is not practicable to design the concrete mix and use controlled concrete. Moreover, since the quantity of concrete involved is rather small,

ordinary plain or reinforced cement concrete given in IS 456 : 1978 shall be used in overhead line foundations. 11.2 Mixes For main foundation, M 150 or 1 : 2 :4 mix cement concrete shall be used. For lean concrete 6

9.1 CJassification of soil shall be made according to IS 1498 : 1970 for footings cast in open pits. It shall, however, be noted that for all the classifications Iisted therein the soil may be dry or wet. 9.2 Dry soil shall be that wliere subsoil water is met below the foundation base. In the `wet' category, classifications shall be as under: a) Wet Where sub-soil water rises in the pit up to 1'5m below ground level; or where there is water over the ground for long periods b

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ut does not penetrate beyond 1 m below ground such as paidy fields; b) Partiallysubmerged Where water rises in the pit within 0'75 m below ground level; and C)Fully submerged Where sub-soil water rises in the pit below ground level. 1D STUB-SETTING ( OR TOWER FOOTING )

10.1 For the purpose of stub-setting, the top chord pieces of the adjustable frames shall have

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IS 5613 ( Part 3/&c 2_) : 1989 sub-bases or pads, M 100 or f : 3 : 6 mix cementconcrete may be used. The properties of concrete and mix proportions shall be asgiven in IS 456 : 1978. It shall be permissible crete as follows: to proportionate the con-

a) Prepare a wooden measuring box of ~35 litres capacity ( that is, equal to 1 bag or 50 kg of cement ) with inside dimensions of ( not exceeding 30 x 30 x 30 cm ) alternatively 34 cm diameter and 39 cm height. The mix quantities accordingbox shall be as follows: M 150 1 bag Cement 2 boxes Sand 4 boxes Stone 1 box less Water 3 litres to the measuring M 100 1 bag 3 boxes 6 boxes 1 box less 1 litre

FIG. 4

FORM WORK FOR SLABS/PYRAMIDS

b) Measurement of water may be made with separate water-tight drums of the abovesize or with l- or 2-litre mugs.NOTE - For concreting the bored foundations by displacing the drilling muds, 10percent extra cement in the mix is required.

removed from the interior of the forms before the concrete is placed. The surface in contact with the concrete shall be wetted and sprayed with fine sand, or treated with an approved composition before use, every time. Concreting to be donefor cold weather shall be as per IS 7861 ( Part 2 ) : 1981. 11.3.4 Stripping Ti

me Under fair weather conditions ( generally where average daily temperature is20C or above ), and where ordinary cement is used, forms may be struck after 24 to 48 hours of the placing of concrete. In dull weather such as rainy periods very cold temperature, the forms shall be struck after 48 hours of the placing of concrete. 11.3.5 Procedure When Removing Form Work All form work shall be removedwithout such shock or vibration as would damage the concrete or the forms.. 11.4 Back Filling Following opening of form work and removal of shoring and strutting, if any, back filling shall be started after repair, if any, to the foundation concrete. Back filling shall normally be done with the excavated soil, unlessit consists of large boulders/stones, in which case the boulders shall be brokento a maximum size of 80 mm. The back filling materials should be clean and freefrom organic or other foreign materials. The earth shall be deposited in maximum 200 mm layers, levelled and wetted and tamped properly before another layer is

deposited. Care shall be taken that the back filling is started from the foundation ends of the pits, towards the outer ends. After pits have been back filledto full depth, the stub template may be re,moved. 7

112.1 One bag of cement is taken to contain 50 kg or 35 litres of ordinary portland cement.

11.3 Form Work 11.3.1 General The form work shall conform to the shape, lines and dimensions as shown on the design drawings, and be so constructed as to be rigid during the placing and compacting of concrete, and shall be sufficiently tight $0 prevent loss of liquidfrom concrete. It shall be of light design easily removable without distortions and shall be of steel hardwood or framed plywood. Theinner surface coming in contact with concrete shall be smooth and free from pro

jections, Window on one face shall be provided for pyramid forms to facilitate concreting in the lower parts which shall %e fixed after concrete in the bottom part is placed. In bored footings form work may be needed only towards the top for the portion above ground level. 11.3.2 The form work for slabs and pyramids shall be made symmetrical about the base of the chimney to ensure interchangeable.faces as illustrated in Fig. 4. 11.3+3 Clearing and Treatment of Forms All rubbish, particularly chippings, shavings and sawdust and traces of concrete, if any, shall be

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IS 5613 ( Part 3/Set 2 ) : 1989

The back filling and grading shall be carried to an elevation of about 75 mm above the finished ground level to drain out water. After back filling 50 mm high earthen embankment ( bandh ) will be made along the sides of excavated pits and sufficient water ~111 be poured in the back filled earth for at least 24 hours. 11.5 Reinforcement All reinforcement shall be properly placed a&ording to designdrawing with a minimum concrete cover of 50 mm. The bars shall, however, be placed clear of stubs and cleats where interfering. For binding, iron wire of not less than 0'9 mm shall be employed, and the bars may be bound at alternate crossing points. The work shall conform to IS 2502 : 1963 wherever applicable. For bored footings, stub angle shall be used as reinforcement. In case of the foundationhaving steel reinforcement in pyramid on base slab, at least 50 mm thick pad oflean concrete of 1 : 3 : 6 nominal mix shall be provided to avoid the possibility of reinforcement rod being exposed due to unevenness of the bottom of the excavated pit. 11.6 Sizes of Aggregates The coarse aggregates ( stone ) to be usedshall be single size aggregates of 40 mm nominal size for slab/pyramid concreteand 20 mm nominal size for chimney concrete conforming to IS 383 : 1970. These sizes are applicable to ordinary plain cement concrete for RCC the aggregates shall preferably be of 20 mm nominal size. The fine aggregate ( sand ) shall be ofZone I Grade to tS 383 : 1970 which i$ the coarse variety with maximum particlesize of 4'75 mm. Zone II Grade of fine aggregates may also be used. 11.7 GravelSub-base In case the foundation happens to be over fine sand, 80 mm thick gravelsub-base may be provided, if considered necessary, under the foundation. The ma

ximum size of gravel or stone to be used shall be 80 mm. 11.8 Curing The concrete after setting for 24 hours old shall be cured by keeping the concrete wet continuously for a period of 10 days after laying. The pit may be back filled with selected earth sprinkled with necessary amount of water and well consolidated inlayers not exceeding 200 mm of consolidated thickness after a minimum period of24 hours and thereafter both the aback filled earth and exposed chimney top shall be kept wet for the remainder of the prescribed time of 10 days. The uncoveredconcrete chimney above the back filled earth shall be kept wet by providing empty cement bags dipped in water fully wrapped around the8

eonerete chimney for curing and ensuring that the bags are kept wet by the frequent pouring of water on them. 11.9 Measurement of Conerete Except where actual p

it size concrete is required ( such as in a rock foundation ), the volume of concrete shall be calculated from the design drawings. All volumes shall be expressed to the nearest cubic metre. The heights used for calculating concrete volumesshall be the projected heights used and not those following the tower slope; the top of the pyramid concrete shall be considered to be same as the chimney cross section for purpose of calculating the volumes, even though it is greater on account of the chimney slope. 11.9.1 The method of measurement of concrete for pile foundations is given as below. 11.9.1.1 Approximate volume of short bored under-reamed piles is calculated by the following formula: Volume in cubic metre =-[LLa+0'4n(d,--)(~"--k)l ( see Fig. 5 ) -where L = total length of pik in metres;d = diameter of pile shaft in metres;du = diameter of under-ream

in metres ( 2 or 3 times d ), normally 2'5 d; and

n = number of under-reams. Distance between two under-reams 1'5 du ; lS5 to

Spacing between piles = 2'0 d, ; or 1'5 du with 10 percent reduction in capacity. 11.10 Mixing, Placing and Compacting of Concrete This shall be carried out according procedure laid down in Annex D. 12 PROTECTION OF TOWER FOOTING to the

12.1 The work shall include a11 necessary stone revetment, concreting and earthfilling above ground level and the clearance from stacking on the side of all su

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rplus excavated soil, specia1 measures for protection of foundations close to orin nallahas, river ~beds, etc. by providing suitahle revetment or galvanized wire netting and meshing packed with boulders. The contractors shall furnish recommendations for providing proteo tion at such locations.

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IS 5613 CPart 3/Set 2 ) : 1989 a lug for connection to the tower leg at one end.The wires are connected to each of the legs and taken radially away from the tower and embedded horizontally 1 m below ground level. The length of each wire isnormally limited to 25 m, but may be increased if the resistance requirements are not met. The size of the galvanized steel stranded wire may be taken equal tothe sizes of the earth conductor. A typical example of counterpoise type earthing of tower is given in Fig. 7. 14 TOWER ERECTION 14.1 General Towers shall be erected after the concrete is at least 14 days old, but a gap ~of 28 days shall be preferred. 14.2 Inspection and Sorting Out The members shall be examined for defects in protective surface finish, if any. If any defects are found in case ofhot dip galvanized members, the damage shall be repaired by applying two coatsof zinc-rich paint having at least 90 percent zinc content conforming to relevant Indian Standard after cleaning the surface and ensuring that the surface is ~dry before the application of the paint. Members bent in transit shall be straightened such that the protective surface finish is not damaged. All the members shall be sorted out properly at the erection ~site to check that all items are available; and shall be placed in a manner such that they are easily located duringerection. 14.3 Treatment of Joints Before starting assembly, specially for thelines in coastal or highly polluted areas, the surfaces at connection points shall be applied a coat of aluminium or zinc-rich paint in case of galvanized members, and red oxide or zinc chromate paint in case of painted members. 14.4 Assembly Irrespective of the method followed for the erection of towers, the points mentioned below shall be observed: / Straining a> of the members shall not be permitted for bringing them into position. It may, however, be necessary to match ho

ld positions at joints and to facilitate this, tommy bars not more than 450 mm long may be used. the lower section shall be completely braced and all bolts fitted in accordance with approved drawings.

FIG.5

TYPICALDETAILS OF UNDERREAMED PILES

13 EARTHING13.1 Each tower shall be earthed after the foundation has been cast. For this purpose, earth strips shall be fixed to the stub during concreting of the chimneyand taken out horizontally below the ground level. In normal circumstances, theearth strip shall be provided on No. 1 stub leg as given in Fig. 3, that is, the

leg with step bolts. 13.2 The resistance of tower to earth shall not exceed 10ohm after earthing and tower erection but before stringing of the overhead ground wire. In case, the resistance exceeds the specified values, multiple pipe earthing or counterpoise earthing shall be-adopted in accordance with the followingprocedure, but without interfering with the foundation concrete even though theearth strip/counterpoise lead remains exposed at the tower end. The connectionsin such case shall be made with the existing lattice member holes on the leg just above the chimney top. 13.3 Pipe Earth The installation of the pipe earth shall be in accordance with IS 3043 : 1987. A typical example of earth in equipment( pipe type ) is given in Fig. 6. 13.4 Counterpoise Earth Counterpoise earth consists of four lengths of galvanized steel stranded wires, each fitted with

b) Before starting erection of an upper section

9

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IS 5613(Part 3/!&c 2):1989

2 BOL

Sx-6-OmmlMK:Kx5m

LO

-6 mm c# OPEN

HO

MATERIAL Quantity 1 1 2 2 4 Description 25 mm bore GI pipe 45 x 6mmMSffat 16 mmdia bolts with nuts 16 mm dia bolts with nuts Plain washer for 16 mm dia bolts

LIST Length (mm) 3 000 5 oao 38 Suit stub Weight (kg) 11'88 15'50 0.16

To

NOTES 1 All ferrous parts are hot-dip galvanized 2 In case of difficult location, horizontal or fundation pit shall be permissible.Or

slant laying of pipe aad iaying, in millimetres.

within the tower base

All dimensions

FIG. 6 A TYPICAL EXAMPLE OF EARTHING EQUIPMENT 10

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IS 5413 ( Part 3/See 2 ) : 1989 been inserted under each nut. In case of step bolts, spring washer shall be placed under the outer nut. The tightening shall progressively be carried out from the top downwards, care being taken that all bolts are at every level are tightened simultaneously. It may be better to employ four persons, each covering one leg and the face to his left. 14.5.1 The threads of bolts projecting outside nuts shall be punched at three positions on the diameter to ensure that the nuts are not in loosened course of time. If during tightening a nut is found to be slipping or running over the bolt threads, the bolt together with the nuts shall be changed out-right. 14.5.2 The threads of all the bolts projected outside the nuts~shall be welded at two diametrically opposite places. The length of each welding shall be at least 10 mm. The welding shall be provided 1from ground level to waist level for single circuit towers and to bottom cross-arm level for double circuit towers. After welding cold galvanizing i paint with at least 90 percent zinc content shall be 1applied to the welded portion. 14.6 Replacement If any replacements are to be `efYe&d after stringing and tensioning or during maintenance, leg members and main bracings shall not be takenout without reducing the tension of the tower with proper guying or releasing the conductor. If the replacement of cross-arms becomes necessary after stringingthe conductor shall be suitably tied to the tower at tension points or transferred to suitable roller pullies at suspension points. 15 INSULATOR HOISTING

d LABLE

I-

TERMINALS

6mm

THICK

JOINT SOLOERED OR COMPRESSED

713-O STEEL CONDUCTOR OR AS AVAILABLE .

All dimensions in millimetres.

FIG. 7

TYPICAL EXAMPLEOF COUNTERPOISE TYPE OF EARTHING OF TOWER

All plan diagonals relevant to a section of tower shall be placed in position before assembly of upper section is taken up. All bolts shall have theirnuts facing outside of the tower for horizontal or nearly horizontal bolt connections anddownwards for vertical bolt connections.

4 The cross-arms may be assembled on ground

and the top cross-arm shall be lifted first, followed by the middle and bottom crossThe tips shall be fully tightened arms. before lifting them into position. S

uch bolts which are not assessible for tightening by ordinary tommy spanners, may be tightened with the help of box or ratchet ring spanners. plete erection oftower, are to be filled up by bolts and nuts of correct size.

f) All the blank holes, if any left, after com14.5 Tightening and Punching of Bolts and Nuts

15.1 Suspension insulator strings shall be used on suspension towers and tensioninsulator strings on angle~and dead end towers. The strings shall be fixed on the tower just prior to the stringing of conductors. Damaged insulators and fitti

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ngs, if any, shall not be employed in the assemblies. Before, hoisting, all insulators shall be-cleaned in a manner that will not spoil, injure or scratch the surface of the insulator, but in no case shall any oil be used for the purpose. Corona control rings shall be fitted in an approved manner. The yoke arrangementsshall be horizontal for tension and longitudinal for suspension strings. 16 HAPTFLING OF CONDUCTOR EARTHWIRE AND

All nuts shall be tightened properly using correct size spanners. Before tightening it will be seen that filler washers and plates are placed in relevant gaps -between members, bolts of proper size and length dare inserted, and one spring washer has 11

16.1 While running out the conductors care shall be taken such that the conductors do not touch and rub against the ground or objects which could cause scratches or damage to the strands. The conductors shall be run out of the drums from the top in order to avoid ~damage due to chafing.*

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IS 5613 ( Part 3/Set 2 ) : 1989

Immediately after running out, .the conductor shall be raised at the supports tothe levels of the clamp and placed into the running blocks. The groove of the running blocks shall be of such a design that the seat is semi-circular and larger than the diameter of the conductor earthwire and it does not slip over or rubagainst the sides. The grooves shall be lined with hard rubber or neoprene to avoid damage to conductor and shall be mounted on properly lubricated bearings. 16.2 The running blocks shall be suspended in a All manner to suit the design of the cross-arm. running blocks especially those eat the tensioning and, will be fitted on the cross-arms with jute cloth wrapped over the steel work and under theslings to avoid damage to the slings as well as to the protective surface finish of the steel work. In case suspension or section towers are used even for temporary terminations, if this be unavoidable, they shall be well guyed and steps shall be taken to avoid damage. The drums shall be provided with a suitable breaking device to avoid damages, loose running out and kinking of the conductor. Theconductor shall be continuously observed for loose or broken strands or any other damage. When approaching end of a drum length at least three coils shall be left when the stringing operations are to be stopped. These coils are to be removed carefully, and, if another length is required to be run out, a joint shall bemade as per the recommendations of the conductor manufacturers. 16.3 Repairs toconductors, if necessary, shall be carried out during the running out operations, Repairing of conductor with repair sleeves. surface shall be done only in case of minor damage, scuff marks, etc, keeping in view both safe requirements. ele

ctrical and mechanical Number of damaged strands shall not exceed 1/6th of the total strands in the outer layer. The final conductor surface shall be clean, smooth and shall be without any projection, sharp points, cuts, abrasions, etc. 16.4 Adequate steps shall be taken to prevent clashing of sub-conductors from paying out to the installations of the spacers/spacer dampers. Care shall be taken that both sub-conductors of a bundle are from the same conductor supplier and-preferably from the same batch SO that creep behaviour ofthe sub-conductor remains identical. During sagging care shall be taken to eliminate differential sags in the sub-conductor. as far as possible. However, in no case the sag mismatching ofmore than 40 mm shall be allowed. 16.5 Conductor splices shall be so made thatthey do not crack or get damaged in the stringing operation. The contractor shall use only such equipment/methods during conduc!or .stringing which ensures complete compliance In this regard.

16.6 Derricks shall be used where roads, rivers, channels, telecommunication oroverhead power lines, railway lines, fences or walls have to be crossed during stringing operations. It shall be seen that normal services are not interrupted or damage caused to property. Shut down shall~be obtained when working at crossing of overhead power lines.

16.7 The sequence of running out shall be from top to downwards, that is, the earthwire shall be run out first, followed by the conductors in succession. Unbalances of loads on towers shall be avoided as far as possible. Outer phases of line conductor-shall be strung before the stringing of the middle phase is taken up. 16.8 The proposed 400 kV transmission line may run parallel for certain distance with the existing 220 kV, 132 kV lines which may remain energized during the

stringing period. As a result there is a possibility of dangerous voltage buildup due to electromagnetic and electrostatic coupling in the pulling wire conductors and earthwires, which although comparatively small ~during normal operationscan be severe during switching. Adequate safety precautions are to be taken toprotect workmen and others working on line from this potential danger by way ofproviding travelling ground. 17 STRINGING EARTHWIRE OF CONDUCTOR AND

17.1 The stringing of the conductors shall be done by control tension method, with the help of tension stringing equipment. The equipment shall be capable of maintaining a continuous tension. The maximum tension imposed on a conductor durin

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g stringing operations shall not exceed than that necessary to clear obstructions on the ground. In general stringing tension of about one-half of sagging tension is a good criterion. 17.1.1 Controlled stringing method suitable for simultaneous stringing of the sub-conductor shall be used. Both the conductors making one phase bundle shall be pulled in and-paid off simtiltaneously. Both the conductors of the bundle shall be of matched length. After being pulled the conductor/earthwire shall not be allowed to hang in the stringing blocks for more than 96 hours before being pulled to the specified sag. 17.2 Stringing of Earthwire Stringing of earthwire shall be carried out by conventional stringing method. 17.3 The contractor shall give complete details _of the stringing methods which he proposes to follow. Before the commencement of stringing the contractor shall submitthe stringing charts. for the 12

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IS 5613 ( Part 3/Set 2 ) : 1989 conductors and earthwire showing the initial andfinal sags and tension for various temperatures and spans, along with equivalant spans in the lines for the dpproval of the owner. 18 JOINTS 18.1All the jointson the conductor and earthwire shall be of compression type, in accordance withthe recommendations of the manufacturer for which all necessary tools and equipment like compressors, dies process, etc, shall have to be arranged by the contractor. Each part of the joint shall be cleaned by wire brush to make it free ofrust or dirt, etc. and properly greased with anticorrosive compound before the final compression is done with the compressors. 18.2 All!joints or splices shallbe made at least 30 metres away from the structures. No joints or splices shallbe made in spans crossing over main roads, railways, small rivers in tension spans. Not more than one joint per sub-conductor shall be allowed in one span. Thecompression type fitting used shall be of self-centring type or care shall be taken to mark the conductors to indicate when the fitting is centred properly. During compression or splicing operation, the conductor shall be handled `in such amanner as to prevent lateral or vertical bearing against the dies. After pressing the joint the aluminium sleeve shall have all corners rounded, burrs and sharp edges removed and smoothened 19 SAGGING-IN-OPERATION 19.1 The conductors shallbe pulled up to the desired dag and left in running blocks for at least one hour after which the sag shall be rechecked and adjusted. if necessary, before transferrmg the cbnductors from the running blocks to be suspension clamps. The conductors shall be clamped within 56 hours of sagging in. 19.2 The sag will be checked in the first and the last span of the section in case of sections up to eight spens and in one intermediate span also for sections with more than eight span

s. The sag shall also be checked when the conductors have been drawn up and transferred from running blocks to the insulator clamps. 19.3 The running blocks, when suspended from the transmission structure for sagging shall be so adjusted that the conductors on running blocks will be at the same height as the suspensionclamp to which it is to be secured. 19.4 At sharp vertical angles, the sags andtensions shall be checked on both sides of the angle, the conductor and earthwire shall be checked on the running blocks for equality of tension on both sides.The suspenrion insulator assemblies will 13 normally assume vertical conductoris clamped. positions when the

19.5 Tensioning and sagging operations shall be carried out in calm weather whenrapid changes in temperatures are not likely to occur. 20 TENSIONING AND SAGGING OF CONDUCTORS AND EARTHWIRE 20.1 The tensioning and sagging shall be done in a

ccordance with the approved stringing charts before the conductors and earthwireare -finally attached to the towers through the earthwire clamps for the earthwire and insulator strings for The `initial' stringing chart shall the conductor.be used for the conductor and `final' stringing chart for earthwire should be employed for this purpose. Dynamometers shall be -employed for measuring tensionin the conductor and earthwire. The dynamometers employed shall be periodicallychecked and calibrated with the standard dynamometer. 21 CLIPPING IN

21.1 Clipping of the conductors in position shall be done in accordance with therecommendations of the manufacturer. Conductor shall be fitted with armour rodswhere it is made to pass through suspension clamps. 21.2 The jumpers at the section and angle towers shall be formed to parabolic shape to ensure maximum clearance requirements. Pilot suspension insulator string shall be used, if found nec

essary, to restrict the jumper swings to the design values. 21.3 Fasteners in all fittings and accessories shall be secured in position. The security clip shallbe properly opened and sprung into position. 22 FIXING OF CONDUCTOR EARTHWIRE ACCESSORIES AND

22.1 Spacers, spacer dampers, vibration dampers and other conductor and earthwire accessories shall be installed by the contractor as per the design requirements and respective manufacturer's Spacers shall be fitted within 24 instructions.hours of the conductor clamping. While installing the conductor and earthwire accessories proper care shall be taken to ensure that the surfaces are clean and s

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mooth~and no damage shall occur to any part ~of the accessories. Spacing bicycle/ trolley may also be used for fixing conductor accessories. 23 TESTING 23.1 General 23.1.1 Before the line is energized, visual AND COMMISSIONING

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IS 5613 ( Part S/SW 2 ) : 1989

examination of the line shall be carried out to check that all nuts and bolts are tight and insulators are in position at each support. The earth and earth connections shall also be checked to verify that these are in order. The insulatorsof those sections of the line which fall in areas of heavy pollution shall be cleaned and washed before energization of the line. 23.2 Testing23.2.1 Before commissioning of the lines, the following tests may be carried out:

The patrollers should write the insuection notes and -pass them on to the maintenance gang for carrying out the necessary repairs. The patrollers should be equipped with inspection books, drawings, tape and binoculars. The main points to benoted while patrolling are as follows: a) Structures Seriously leaning structures; deformed members; buckled structures; missing fasteners and members; accessories removed; protective coatings, like galvanizing or paints disappeared; suspension and strain attachments for insulators damaged. b) Foundations Signs of external damage; settled and washed out soil below designed ground level over. foundations within uplift frustum perimetres; tilted stubs; cracks or breaks in chimney top; slippage of stubs from encasing chimney concrete; uneven settlement offooting; disappearance of gravel blanket protection; backfills embankment and its covers ( rip-rap or revetment ); damage to retaining walls, abutments and breast walls and disappearance of externa1 earth backing retaining walls below designed lines.

Insulators and$ttings

a) Conductor continuity test The Objective of this test is to varify that each conductor of the overhead line is properly connected electrically ( that is, thevalue of its electrical resistance does not vary abnormally form that of a continuous conductor of the same size and length ). The electrical resistance of theconductor shall be measured with a wheatstone bridge or other suitable instrument. b) Insubtion resistance test This test may be carried out with the help of 5000 volts megger preferably power driven to ascertain the insulation condition of line. 23.2.2 The line may be charged at a low value of power frequerey voltage~for the purposes of testing. 23.3 Statutory Requirements 23.3.1 The statutoryauthorities shall be informed before commissioning the lines and their approvalobtained in accordance with Indian Electricity Act, I9IO and Zhdian Electricity

Rules 1956 (For details, see Rule 63 to 69 of Indian ElectricityRules, 1956 ). 24 MAINTENANCE

Damage to insulators; surface pollution of a bad nature; missing locking deviceslike nuts, washers and pins; burnt out fittings; deflected strings; damage to protective The cracked insulators, bird coatings. droppmgs, dense spider webs, kites with cord hanging on the insulators string may also be noted.Conductors andjumpers

OF OVERHAD LINES

24.1 General The overhead lines shall be inspected periodically for maintenancepurposes to detect any faults which may lead to breakdown of electric suppIy and

necessary repairs should be done immediately using hot line maintenance techniques, if necessary and feasible.Ground

Strands cut and opened up, Ioose jumpers gone out of shape and causing infringement of clearance of live wire to earthed metal parts. Dead birds, fallen branches or fallen trees on conductors may also be noted. Earthwire and jumper, in aocordance 24.1 of this standard. f) Earthing equipment, damaged, missing earth strip. g) Right-of-way and clearance Shrubs and trees within right-of-way causing obstruction, and infringement of clearance of bottom conductor to ground; objects

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within line clearance excavation circumstances. ( see Fig. I ). In no 14 brokenwith or

24.1.1 Patroiling

of

Overhead

Lines

from

the

Patrolling of all overhead lines shall be done before and after the monsoon. Thefrequency of patrolling of the overhead lines for the rest of the period shalldepend on the local conditions.

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IS 5613 ( Part 3/k however, clearance measurement should be taken from live line, till hot line maintenance has been established. h) Foreign objects Construction works near lines causing infringement in line safety or electrical clearance;bird nests on structures; use of structure for applying permanent support or pull to other objects; huts newly constructed underneath lines, also embankments/ fencing. 24.2 Inspection Tops of Overhead Lines from Tower

2 ) : 1989

decreas in this interval but it should not be less than once in two years. 24.4.1 The clearance and shaps of the jumpers should be checked at an interval not exceeding 3 years. 24.5 Line Repairs Tools The following special tools, apart fromtools required for maintenance of civil works of the lines, should be kept handy and.in working order: a) Conductor jointing tools, b) Bolted come-alongs. c) Winches, 4 Aerial trolleys, Aerial rollers, e> f>Thermometers, g) Dynamometers, h) Level and theodolite, 3 Measuring tapes, k) Linesmen's ratchet, Pull-lift device of adequete capacity, 4 Wire ropes, and PI Spanners,

Many breakdowns-including slipping of conductor due to loose clamps, cracks in insulator porcelain, defects in insulator fittings, conductor, earthwire and their accessories and their attachment points on structures can only be dispersed orseen by going on top of every structure. This inspection should be carried outby taking a shutdown of the line at least once in six years and should be done in the shortest time possible during seasons of comparatively light climate and p

ower loading on the line'. Along with such inspection, repairs should also be carried out. Any replacement as required should also be made. 24.3 Special and Emergency Inspection A special inspection of the overhead lines should be carried out after severe wind/hail storms, quakes, sabotages, snowfalls, forest fires, floods or heavy rains. The purpose of such inspection is to detect any damage or breakage on line and to affect necessary repairs. 24.3.1 When an overhead line trips on fault often, it should be inspected to ascertain the nature of fault, such as bridge loose sag, tree branches touching the line, et!, and to find out theamount of repair involved with a view to avoid recurrence of such faults. 24.4Maintenance Tests and Measurements Insulation of line should be measured at convenient interval particularly at the time when the line is shutdown for repairs or maintenance. In regard to measurements Of earth resistance of metal structures, it should normally be carried out annually, however, local circumstances in th

e light of the experience may justify increase or

m>

24.51 Drawings Sets of tower schedules, structural, foundation, insulators and accessories or route profile drawing including those for special constructions bound in folders should be available with patrollers as well as the maintenance crew. 24.5.2 Replacement An inventorv of spare line materials shall be maintainedii the stores for effecting repairs. Such inventory should be based upon the experience of repairs required in the earlier periods on similar other lines. 24.5.3 Method of Repairs Damage to aluminium strands of line conductors shall be repaired with repair sleeves provided not more than one-sixth of the strands in theoutermost layer have been severed. For portions adjacent to armour rod ends affe

cted by vibrations due to wind, and minor abrasions due to some rubbing objects,extra-long preformed armour rods may be used for such repairs.

15

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IS 5613 ( Part 3/&c 2 ) : 1989

ANNEX

A

( Clause 2.1 )LIST OF REFERRED INDIAN STANDARDS IS

No.

Title

IS No.

Title

IS 383 : 1970

Specification for coarse and fine aggregates' from natural sources for concrete( secondrevision )

IS 3043 : 1987 IS 3764 : 1966 IS 4081 : 1986

Code of practice for earthing(j&St revision )

IS 456 : 1978

Code of practice for plain and reinforced concrete ( thirdrevision )

Safety work

code for

excavation

Safety code for blasting and related drilling operations( jirst revision )

IS 1199 : 1959 IS 1498 : 1970

Methods of sampling analysis of concrete

and IS 4091 : 1979

Classification and identification of soils for general engineering purposes (Jirst revision ) Electrotechnical vocabulary : Part 30 Overhead, transmission and d

istribution of electrical .energy Code of practice for bending and fixing of bars for concrete reinforcement IS 7861 ( Part 2 ) : 1981

Code of practice for design and construction of foundations for transmission line poles ~(first towers andrevision )

IS 1885 (Part30):1971

IS 2502_: 1963

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IS 5613 ( Part 3/Set 2 ) : 1989 both shorter and longer than the ruling span. Any particular span is considered spread-out by half of its value on either side of origin `0'. B-1.2.3 The parabola is accurate to within about one half of 1 percent for sags up to 5 percent of the span which is well within the acceptable limits. B-l.3 The actual ruling spans for various stringing sections of a line maydiffer from the normal design span which forms the basis for the sag template.It is, therefore, essential that the actual ruling spans be as near the normal design spans as practicable. In case of considerable amount of difference the following points shall be observed: a) The Actual RulingSpan Shorter Than the Normal Design Span

left and right of the centre line up to a distance equal to the maximum swing ofconductor including cross-arm spread on either side. B-2.2 The `weight span' oneither side of the tower for practical purposes is obtained by marking the lowpoints of the sag in the two adjacent spans and sealing the same off. B-2.2.1 Onsteep inclined spans the low point may fall beyond the lower support; this indicated that the conductor in the uphill span exerts a negative or upward pull onthe lower tower. The amount of this upward pull is equal to the weight of the conductor from the lower tower to the low point in the sag. Should the upward pullof the uphill span be greater than the downward load of the next adjacent span,actual uplift would be caused and the conductor would tend to swing clear of the tower upward. B-2.2.2 For an easy check whether a tower is under uplift or not, the following method may be adopted. The template is applied horizontally until the tops of alternate supports coincide with the cold template ( curve I ). If

the curve is above the intermediate support, the support is under uplift and has to be extended until it touches the cold template and so eliminates uplift. Ifrequisite standard body extensions are not available for extending the tower todesired height. a tower designed for uplift shall have to be provided.NOTE-The suspension towers shall be checked for uplift under normal working condition only, that is, both adjacent spans intact. The section and angle towers shall be checked for uplift under both normal and broken wire conditions,

In this case the maximum working and other tensions are comoarativelv less. andtherefore, the sags, comparatively grkater than those obtained for the normal design span. The sag template, therefore, needs to be modified. An easier method shall be to provide suitably greater ground clearance while carrying out tower spotting.

b)

The Actual Ruling Span Longer Normal Design Span

Than the

In this case the maximum working and other tensions are comparatively greater, and therefore, the sags comparatively less, than those obtained for the same spanfrom the volues for the normal design span. Obviously, greater tensions cannotbe allowed on towers; and therefore, by working back with maximum working tension for normal design span we may get different sags at the actual ruling spans. This shall be suitably accounted for while carrying out tower spotting. B-l.4 The

template shall be prepared to the same scale as the survey chart, that is, 1 :2 000 for horizontal distances and 1 : 200 for vertical heights. The vertical centre line and the horizontal line passing through origin `0' shall be drawn prominently. -The curves shall be extended such that all slopes on the profiles may,be scaled with ease. B-2 APPLICATION FOR TOWER SPOTTING

B-2.2.3 The analytical method weight span is given below:

for

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calculating

Distance of `Null point' or `Low point' of conductor from centre of span is giv,en by the formula ( see Fig. 8 and 9 ):X=wf Th

where X=T= h = w= I =

B-2.1 The method of application of the sag template is shown in Fig. 2. The template is applied to the profile by moving the same horizontally as shown while always ensuring that the vertical axis or centre line is held vertical. The structure positions are marked where the `Support foot' cuts the profile, while the `Ground clearance' curve is just clear of and above the profile. The `ground clearance' curve shall not only clear the route-centre line profile, but also the profile to the 17

distance of low point from centre of span in m, conductor tension in kgf, difference between conductor port levels in m, unit weight of conductor and span length in m. sup-

in kg/m,

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.

IS 5613( Part 3fSec2 ) : 1989 WeigJU span: For tower A, right hand side only: a=--x Fortowert 2

If the sum of &and b. calculated for a particular tower is negative, the tower is under `uplift'. It is also evident that maximum weightspans are obtained by the worst conditiun of wind loading when T is maximum; which means the vertical component of worst load sag should be taken for `cold curve' of sag template m order to assess uplift on towers.

B, left hand side only: b = -`_ + X

Similarly, weight span for the other side of the towers, ean be calculated and total weight span obtained.

LOW OR

tow oti' NULL. POW

NULL POLNT

FIG. 8 DISTANCEOF NULL POINT OR Low POINTFROM THE CENTRE OF SPAN

FIG. 9

DISTANCE OF NIJLL POINT OR Low POINT'CENTRE OF SPAN

ANNEX

C

(`Czause 1'0.2.1 )TOLERANCES Cd SURVEY C-l.1 The accuracy of~survey work depends upon, the accuracy of surveying instruments, the prethe accuracy of placing vailing temperatures,and their reading. It shall be instruments ensured, however, that no measuremen

ts should be missed during surveys and check surveys carried out where any doubtarises. C-2 STUB-SETTING ( TOWER FOOTING ) IN OVERHEAD LINE CONSTRUCTION shallnot differ from the computed elevation by more than l/100 of foundation depth. Stub angles shall be located horizontally so that each is within 6 mm of its correct position, and the batter of the stub angles shall not differ from the correct batter by more than either l/100 of erposed stub length, or by the amount of play as offered by the clearance between bolts and holes of the setting template.To ensure greater accuracy, the hole clearance shall not be greater than 1'5 mmof the punched side of the template members. C-2.2 If the actual elevation of stubs is beyond 6 cm as found after casting the foundation is on the plus side (that is, if the foundation is raised ), equivalent depth of earthwork will be provided over the top of the foundation as.per design requirements with particularreference to

C-2.1 All the stub angles for tower legs shall be set accurately to the grade and alignment shown on the drawings, The difference in elevation between identicalparts of any two stub angles shall not exceed l/l 000 of the horizontal` distance between the stubs, allowance being made for the difference, if any, in the lengths of legs -and extensions. The actual elevation of any stub angle 18

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IS 5613 ( Part 3/Set 2 ) : 1989 such location. By design requirements is `meantthe earth required to resist uplift forces. C-2.3 The following tolarances shallbe applicable in case of position of foundation as a whole with reference to tower position as spotted on the survey chart: Type of Tower Suspension or intermediate Section or tension ( set at bisection of deviation angle ) Out of From Centre Line of AlignRoute ment 0'25" f25mm From Transverse Centre Line & 250 mm shall be f 5 mm. This shall not be accumulative on height for various parts of thefoundation. C-4 TOWERS C-4.1 No member of a tower shall be -out ~of straightnessby more than one in 1 000. -Members failing the requirement shall be straightened before erection in a manner that shall not damage their properties or the protective finish. C-4.2 The towers shall not be out of vertical by more than 1 in360 before stringing is carried out. C-5 STRINGING C-5.1 The maximum toterance in final still air sag at maximum temparature shall be f4 percent of such sag, inany span as obtained from the sag tension chart. The sag ~of any conductor in aspan shall not depart from the mean sag of all conductors in the same span by more than 3 percent.NOTE-In order that the niinimum required ground clearance is not interfered withby tolerance in sag template used for tower sporting shall be based upon a plustolerance in sag of 4 percent, the `support foot' curve being located according~to tower design.

0'25"

f25mm

*

25mm

C-3 CONCRETE AND FORM DIMENSIONS C-3.1 The maximum tolerance on the dimensions

ANNEX

D

( Clause 11.10) MIXING, PLACING AND COMPACTING OF CONCRETED-l MIXING D-l.1 Concrete shall preferably be mixed in a mechanical mixer, but h

and mixing shall be permissible. In case of emergency ( when mechanical mixers are in use 1 such as failure of the mixers, or where it is not practicable to haul the mixers up to the location, and also for lean concrete sub-base, hand mixing may be resorted to. D-l.2 When hand mixing is adopted, it shall be carried outon water-tight platforms, such as 1'8 mm glavanized iron plain sheets properlyoverlapped and placed upon level ground. The coarse aggregates shall first be evenly spread out in required quantity over the sheets. The fine aggregates shallbe evenly spread out over coarse aggregates next. The aggregates shall than be thoroughly mixed together and levelled. The required amount of cement shall not be spread evenly over the mixed aggregates and wet mixing shall start from one end with required amount of water suing showels. The whole lot shall not be wetted; instead mixing shall proceed progressively. If the agreegates are wet nor washed, cement shall not be spread out, but shall be put in progressively. D-l.3 For

mixing the mechanical mixers, the same order of placing ingredients in the leader/ drum shall be adopted, that is, coarse aggregates shall be put in first followed by sand, cement and water. D-l.4 Mixing shall be continued until there is auniform distribution of material and the mass is uniform in colour and consistency but in no case shall mixing be done for less than 2 minutes. D-l.5 If the aggregates are wet, the amount of water shall be reduced suitably. D-2 TRANSPORTING D-2.1 Normally mixing shall be done right at the foundation. In places where it is not possible, concrete may be mixed at the nearest convenient place. The concrete shall be handled from the place of mixing to the place of final deposit as rapidly as practicable by methods which shall prevent the sagregation or loss

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of any of the ingredients. If segregation does occur during transport the concrete shall be remixed before being placed. 19

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IS 5613 ( Part 3/Set 2 ) : 1989 D-2.2 During hot or cold weather, concrete shallbe transported in deep containers; the deep containers, onaccount of their lower ratio of-surface area to mass, reduce the rate of loss of water by evaporationduring hot weather and loss of heat during cold weather. D-3 PLACING AND COMPACTING bars be worked 100 times in an area of 200 mm square for 300 mm depth. Over-compacting causes the liquid to flow out upward causing segregation and shouldbe avoided. D-3.3 If, after the form work has been struck, the concrete surfaceis found to have defects, all the damaged surfaces shall be repaired with mortarapplication composed of cement and sand in the same proportion as the cement and sand in the concrete mix. Such repairs shall be carried out well before the foundation pits are back filled. D-3.4 For precautions to be taken on concrete work in extreme weather and under water, the provisions of IS 456 : 1978 shall apply. D-3.5 Field tests on workability ~of concrete and consistency may be carriedout in the form of slump test in accordance with IS 1199 : 1959.

D-3.1 The concrete shall be placed and compacted before setting commences and should not be subsequently disturbed. The placing should be such that no segregation takes place. D-3.2 Concrete shall be thoroughly compacted during the placingoperation, and thoroughly worked around the reinforcement, around embedded fixtures and into corners of form work by means of 16 mm diameter poking bars pointedat the ends. As a guide for compacting the poking

-20

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Standard Mark The use of the Standard Mark is governed by the provisions of theBureau of Indian Standards Act, 1986 and the Rules and Regulations made thereunder. The Standard Mark on products covered by an Indian Standard conveys the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testing and quality control whichis devised and supervised by BIS and operated by the producer. Standard markedproducts are also continuously checked by BIS for conformity to that standard asa further safeguard. Details of conditions under which a licence for the use ofthe Standard Mark may be granted to manufacturers or producers may be obtainedfrom the Bureau of Indian Standards.

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Bureau of Indian Standards BIS is a statutory institution established under thehreau of Indian Standardr Act, 1986 to promote harmonious development of the activities of standardization, marking and quality certification of gooda and attending to connected matters in the country.Copyright

BIShas the copyright of all its publications. No part of these publications maybe reproduced in any form without the prior permission in writing of BlS. This does not preclude the free use, in the course of implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. Enquiries relating to copyright be addressed to the Director ( Publications ), BIS. Revision 01 Indian Standards Indian Standards are reviewed periodically and revised,when necessary and amendments, if any, arc issued from time to time. Users of Indian Standards should ascertain that they are in ~possession of the latest amendments or edition. Comments on this Indian Standard may be sent to BIS giving tho foIlowing reference: Dot : No. ETDC 60 ( 2968 )Amendments Issued Since Publfcatioe

Amend NO.

Date of Issue

Text Affected

BUREAU OF INDIA-N STANDARDS HeadquartersManak :

Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telephones : 331 01 31, 33113 75 Regional Offices : Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg NEW DELHI 110002 Eastern : l/l4 C. I. T. Scheme VII M, V. I. P. Road, Maniktola CALCUTTA 700054 Northern :-SC0 445-446, Sector 35-C. CHANDIGARH 160036,

Telegrams : Manaksanstha ( Common to all Offices ) Telephone 331 01 31 { 331 1375 36 24 99 2 1843 1 3 16 41 41 24 42 41 25 19 { 41 29 16 6 32 92 95

Southern : C. I. T. Campus, IV Cross Road, MADRAS 600113

Western : Manakalaya, E9 MIDC, Marol, Andheri ( East ) BOMBAY 400093 Branches :AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR, GUWAHATI. HYDERABAD. JAIPUR. KANPUR.PATNA. PIVANDRUM.

Printed at Prlntwoll Printers, Delhi, India

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