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Vector Group of Transformer

MAY 23, 2012 43 COMMENTS(HTTP://ELECTRICALNOTES.WORDPRESS.COM/2012/05/23/VECTOR-GROUP-OF-TRANSFORMER/#COMMENTS)

Introduction:

Three phase transformer consists of three sets of primary windings, one for each phase, and three sets of

secondary windings wound on the same iron core. Separate single-phase transformers can be used andexternally interconnected to yield the same results as a 3-phase unit.

The primary windings are connected in one of several ways. The two most common configurations arethe delta, in which the polarity end of one winding is connected to the non-polarity end of the next, and

the star, in which all three non-polarities (or polarity) ends are connected together. The secondarywindings are connected similarly. This means that a 3-phase transformer can have its primary and

secondary windings connected the same (delta-delta or star-star), or differently (delta-star or star-delta).

It’s important to remember that the secondary voltage waveforms are in phase with the primary

waveforms when the primary and secondary windings are connected the same way. This condition iscalled “no phase shift.” But when the primary and secondary windings are connected differently, the

secondary voltage waveforms will differ from the corresponding primary voltage waveforms by 30electrical degrees. This is called a 30 degree phase shift. When two transformers are connected inparallel, their phase shifts must be identical; if not, a short circuit will occur when the transformers areenergized.”

Basic Idea of Winding:

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An ac voltage applied to a coil will induce a voltage in a second coil where the two are linked by amagnetic path. The phase relationship of the two voltages depends upon which ways round the

coils are connected. The voltages will either be in-phase or displaced by 180 degWhen 3 coils are used in a 3 phase transformer winding a number of options exist. The coil voltagescan be in phase or displaced as above with the coils connected in star or delta and, in the case of astar winding, have the star point (neutral) brought out to an external terminal or not.

Six Ways to wire Star Winding:

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Six Ways to wire Delta Winding:

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Polarity:

An ac voltage applied to a coil will induce a voltage in a second coil where the two are linked by amagnetic path. The phase relationship of the two voltages depends upon which way round the coils

are connected. The voltages will either be in-phase or displaced by 180 deg.When 3 coils are used in a 3 phase transformer winding a number of options exist. The coil voltages

can be in phase or displaced as above with the coils connected in star or delta and, in the case of astar winding, have the star point (neutral) brought out to an external terminal or not.

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When Pair of Coil of Transformer have same direction than voltage induced in both coil are in same

direction from one end to other end.

When two coil have opposite winding direction than Voltage induced in both coil are in oppositedirection.

Winding connection designations:

First Symbol: for High Voltage: Always capital letters. D=Delta, Y=Star, Z=Interconnected star, N=Neutral

Second Symbol: for Low voltage: Always Small letters. d=Delta, y=Star, z=Interconnected star, n=Neutral.

Third Symbol: Phase displacement expressed as the clock hour number (1,6,11)

Example – Dyn11Transformer has a delta connected primary winding (D) a star connected secondary (y) with the

star point brought out (n) and a phase shift of 30 deg leading (11).The point of confusion is occurring in notation in a step-up transformer. As the IEC60076-1

standard has stated, the notation is HV-LV in sequence. For example, a step-up transformer with adelta-connected primary, and star-connected secondary, is not written as ‘dY11′, but ‘Yd11′. The 11

indicates the LV winding leads the HV by 30 degrees.

Transformers built to ANSI standards usually do not have the vector group shown on theirnameplate and instead a vector diagram is given to show the relationship between the primary and

other windings.

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Vector Group of Transformer:

The three phase transformer windings can be connected several ways. Based on the windings’

connection, the vector group of the transformer is determined.The transformer vector group is indicated on the Name Plate of transformer by the manufacturer.

The vector group indicates the phase difference between the primary and secondary sides,

introduced due to that particular configuration of transformer windings connection.The Determination of vector group of transformers is very important before connecting two or more

transformers in parallel. If two transformers of different vector groups are connected in parallel thenphase difference exist between the secondary of the transformers and large circulating current flows

between the two transformers which is very detrimental.

Phase Displacement between HV and LV Windings:

The vector for the high voltage winding is taken as the reference vector. Displacement of the vectors

of other windings from the reference vector, with anticlockwise rotation, is represented by the use ofclock hour figure.

IS: 2026 (Part 1V)-1977 gives 26 sets of connections star-star, star-delta, and star zigzag, delta-delta,

delta star, delta-zigzag, zigzag star, zigzag-delta. Displacement of the low voltage winding vectorvaries from zero to -330° in steps of -30°, depending on the method of connections.

Hardly any power system adopts such a large variety of connections. Some of the commonly usedconnections with phase displacement of 0, -300, -180″ and -330° (clock-hour setting 0, 1, 6 and 11).

Symbol for the high voltage winding comes first, followed by the symbols of windings in

diminishing sequence of voltage. For example a 220/66/11 kV Transformer connected star, star anddelta and vectors of 66 and 11 kV windings having phase displacement of 0° and -330° with the

reference (220 kV) vector will be represented As Yy0 – Yd11.The digits (0, 1, 11 etc) relate to the phase displacement between the HV and LV windings using a

clock face notation. The phasor representing the HV winding is taken as reference and set at 12o’clock. Phase rotation is always anti-clockwise. (International adopted).

Use the hour indicator as the indicating phase displacement angle. Because there are 12 hours on a

clock, and a circle consists out of 360°, each hour represents 30°.Thus 1 = 30°, 2 = 60°, 3 = 90°, 6 =180° and 12 = 0° or 360°.

The minute hand is set on 12 o’clock and replaces the line to neutral voltage (sometimes imaginary)of the HV winding. This position is always the reference point.

Example:Digit 0 =0° that the LV phasor is in phase with the HV phasor

Digit 1 =30° lagging (LV lags HV with 30°) because rotation is anti-clockwise.

Digit 11 = 330° lagging or 30° leading (LV leads HV with 30°)Digit 5 = 150° lagging (LV lags HV with 150°)



Digit 6 = 180° lagging (LV lags HV with 180°)

When transformers are operated in parallel it is important that any phase shift is the same througheach. Paralleling typically occurs when transformers are located at one site and connected to a

common bus bar (banked) or located at different sites with the secondary terminals connected viadistribution or transmission circuits consisting of cables and overhead lines.

Phase Shift

(Deg)

Connection

0 Yy0 Dd0 Dz0

30 lag Yd1 Dy1 Yz1

60 lag Dd2 Dz2

120 lag Dd4 Dz4

150 lag Yd5 Dy5 Yz5

180 lag Yy6 Dd6 Dz6

150 lead Yd7 Dy7 Yz7

120 lead Dd8 Dz8

60 lead Dd10 Dz10

30 lead Yd11 Dy11 Yz11

The phase-bushings on a three phase transformer are marked either ABC, UVW or 123 (HV-side

capital, LV-side small letters). Two winding, three phase transformers can be divided into four maincategories

Group O’clock TC

Group I 0 o’clock, 0° delta/delta, star/star

Group II 6 o’clock, 180° delta/delta, star/star

Group III 1 o’clock, -30° star/delta, delta/star

Group IV 11 o’clock, +30° star/delta, delta/star



Minus indicates LV lagging HV, plus indicates LV leadingHV

Clock Notation: 0

Clock Notation : 1

Clock Notation: 2

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Clock Notation: 4





Clock Notation: 5

Clock Notation: 6

Clock Notation: 7





Clock Notation: 11

Points to be consider while Selecting of VectorGroup:

Vector Groups are the IEC method of categorizing the primary and secondary windingconfigurations of 3-phase transformers. Windings can be connected as delta, star, or interconnected-

star (zigzag). Winding polarity is also important, since reversing the connections across a set ofwindings affects the phase-shift between primary and secondary. Vector groups identify thewinding connections and polarities of the primary and secondary. From a vector group one can





determine the phase-shift between primary and secondary.Transformer vector group depends upon

Removing harmonics: Dy connection – y winding nullifies 3rd harmonics, preventing it to be

reflected on delta side.Parallel operations: All the transformers should have same vector group & polarity of thewinding.Earth fault Relay: A Dd transformer does not have neutral. to restrict the earth faults in such

systems, we may use zig zag wound transformer to create a neutral along with the earth faultrelay..Type of Non Liner Load: systems having different types of harmonics & non linear Types of

loads e.g. furnace heaters ,VFDS etc for that we may use Dyn11, Dyn21, Dyn31 configuration,wherein, 30 deg. shifts of voltages nullifies the 3rd harmonics to zero in the supply system.Type of Transformer Application: Generally for Power export transformer i.e. generator side

is connected in delta and load side is connected in star. For Power export import transformersi.e. in Transmission Purpose Transformer star star connection may be preferred by some sincethis avoids a grounding transformer on generator side and perhaps save on neutral insulation.Most of systems are running in this configuration. May be less harmful than operating delta

system incorrectly. Yd or Dy connection is standard for all unit connected generators.There are a number of factors associated with transformer connections and may be useful indesigning a system, and the application of the factors therefore determines the best selection of

transformers. For example:

For selecting Star Connection:

A star connection presents a neutral. If the transformer also includes a delta winding, that neutralwill be stable and can be grounded to become a reference for the system. A transformer with a starwinding that does NOT include a delta does not present a stable neutral.Star-star transformers are used if there is a requirement to avoid a 30deg phase shift, if there is a

desire to construct the three-phase transformer bank from single-phase transformers, or if thetransformer is going to be switched on a single-pole basis (ie, one phase at a time), perhaps usingmanual switches.

Star-star transformers are typically found in distribution applications, or in large sizesinterconnecting high-voltage transmission systems. Some star-star transformers are equipped witha third winding connected in delta to stabilize the neutral.

For selecting Delta Connection:

A delta connection introduces a 30 electrical degree phase shift.A delta connection ‘traps’ the flow of zero sequence currents.

For selecting Delta-Star Connection:

Delta-star transformers are the most common and most generally useful transformers.Delta-delta transformers may be chosen if there is no need for a stable neutral, or if there is arequirement to avoid a 30 electrical degree phase shift. The most common application of a delta-delta transformer is as tan isolation transformer for a power converter.



For selecting Zig zag Connection:

The Zig Zag winding reduces voltage unbalance in systems where the load is not equallydistributed between phases, and permits neutral current loading with inherently low zero-sequenceimpedance. It is therefore often used for earthing transformers.Provision of a neutral earth point or points, where the neutral is referred to earth either directly orthrough impedance. Transformers are used to give the neutral point in the majority of systems. Thestar or interconnected star (Z) winding configurations give a neutral location. If for various reasons,

only delta windings are used at a particular voltage level on a particular system, a neutral point canstill be provided by a purpose-made transformer called a ‘neutral earthing.

For selecting Distribution Transformer:

The first criterion to consider in choosing a vector group for a distribution transformer for a facilityis to know whether we want a delta-star or star-star. Utilities often prefer star-star transformers, but

these require 4-wire input feeders and 4-wire output feeders (i.e. incoming and outgoing neutralconductors).For distribution transformers within a facility, often delta-star are chosen because thesetransformers do not require 4-wire input; a 3-wire primary feeder circuit suffices to supply a 4-wiresecondary circuit. That is because any zero sequence current required by the secondary to supplyearth faults or unbalanced loads is supplied by the delta primary winding, and is not required fromthe upstream power source. The method of earthing on the secondary is independent of the primary

for delta-star transformers.The second criterion to consider is what phase-shift you want between primary and secondary. Forexample, Dy11 and Dy5 transformers are both delta-star. If we don’t care about the phase-shift,then either transformer will do the job. Phase-shift is important when we are paralleling sources. Wewant the phase-shifts of the sources to be identical.If we are paralleling transformers, then you want them to have the same the same vector group. Ifyou are replacing a transformer, use the same vector group for the new transformer, otherwise the

existing VTs and CTs used for protection and metering will not work properly.There is no technical difference between the one vector groups (i.e. Yd1) or another vector group(i.e. Yd11) in terms of performance. The only factor affecting the choice between one or the other issystem phasing, ie whether parts of the network fed from the transformer need to operate in parallelwith another source. It also matters if you have an auxiliary transformer connected to generatorterminals. Vector matching at the auxiliary bus bar

Application of Transformer according to VectorGroup:

(1) (Dyn11, Dyn1, YNd1, YNd11)



Common for distribution transformers.Normally Dyn11 vector group using at distribution system. Because Generating Transformer areYNd1 for neutralizing the load angle between 11 and 1.

We can use Dyn1 at distribution system, when we are using Generator Transformer are YNd11.In some industries 6 pulse electric drives are using due to this 5thharmonics will generate if we useDyn1 it will be suppress the 5th harmonics.Star point facilitates mixed loading of three phase and single phase consumer connections.The delta winding carry third harmonics and stabilizes star point potential.A delta-Star connection is used for step-up generating stations. If HV winding is star connectedthere will be saving in cost of insulation.

But delta connected HV winding is common in distribution network, for feeding motors andlighting loads from LV side.

(2) Star-Star (Yy0 or Yy6)

Mainly used for large system tie-up Transformer.Most economical connection in HV power system to interconnect between two delta systems and toprovide neutral for grounding both of them.Tertiary winding stabilizes the neutral conditions. In star connected transformers, load can beconnected between line and neutral, only if (a) the source side transformers is delta connected or

(b) the source side is star connected with neutral connected back to the source neutral.In This Transformers. Insulation cost is highly reduced. Neutral wire can permit mixed loading.Triple harmonics are absent in the lines. These triple harmonic currents cannot flow, unless there is aneutral wire. This connection produces oscillating neutral.Three phase shell type units have large triple harmonic phase voltage. However three phase coretype transformers work satisfactorily.A tertiary mesh connected winding may be required to stabilize the oscillating neutral due to third

harmonics in three phase banks.

(3) Delta – Delta (Dd 0 or Dd 6)

This is an economical connection for large low voltage transformers.Large unbalance of load can be met without difficulty.Delta permits a circulating path for triple harmonics thus attenuates the same.It is possible to operate with one transformer removed in open delta or” V” connection meeting 58percent of the balanced load.Three phase units cannot have this facility. Mixed single phase loading is not possible due to theabsence of neutral.



(4) Star-Zig-zag or Delta-Zig-zag (Yz or Dz)

These connections are employed where delta connections are weak. Interconnection of phases inzigzag winding effects a reduction of third harmonic voltages and at the same time permitsunbalanced loading.This connection may be used with either delta connected or star connected winding either for step-

up or step-down transformers. In either case, the zigzag winding produces the same angulardisplacement as a delta winding, and at the same time provides a neutral for earthing purposes.The amount of copper required from a zigzag winding in 15% more than a corresponding star ordelta winding. This is extensively used for earthing transformer.Due to zigzag connection (interconnection between phases), third harmonic voltages are reduced. Italso allows unbalanced loading. The zigzag connection is employed for LV winding. For a giventotal voltage per phase, the zigzag side requires 15% more turns as compared to normal phase

connection. In cases where delta connections are weak due to large number of turns and small crosssections, then zigzag star connection is preferred. It is also used in rectifiers.

(5) Zig- zag/ star (ZY1 or Zy11)

Zigzag connection is obtained by inter connection of phases.4-wire system is possible on both sides.Unbalanced loading is also possible. Oscillating neutral problem is absent in this connection.This connection requires 15% more turns for the same voltage on the zigzag side and hence costsmore. Hence a bank of three single phase transformers cost about 15% more than their 3-phasecounterpart. Also, they occupy more space. But the spare capacity cost will be less and single phaseunits are easier to transport.

Unbalanced operation of the transformer with large zero sequence fundamental mmf content alsodoes not affect its performance. Even with Yy type of poly phase connection without neutralconnection the oscillating neutral does not occur with these cores. Finally, three phase coresthemselves cost less than three single phase units due to compactness.

(6) Yd5:

Mainly used for machine and main Transformer in large Power Station and TransmissionSubstation.The Neutral point can be loaded with rated Current.



(7) Yz-5

For Distribution Transformer up to 250MVA for local distribution system.The Neutral point can be loaded with rated Current.

Application of Transformer according accordingto Uses:

Step up Transformer: It should be Yd1 or Yd11.Step down Transformer: It should be Dy1 or Dy11.Grounding purpose Transformer: It should be Yz1 or Dz11.

Distribution Transformer: We can consider vector group of Dzn0 which reduce the 75% ofharmonics in secondary side.Power Transformer: Vector group is deepen on application for Example : GeneratingTransformer : Dyn1 , Furnace Transformer: Ynyn0.

Convert One Group of Transformer to Other Groupby Channing External Connection:

(1) Group I: Example: Dd0 (no phase displacement between HV and LV).

The conventional method is to connect the red phase on A/a, Yellow phase on B/b, and the Bluephase on C/c.Other phase displacements are possible with unconventional connections (for instance red on b,

yellow on c and blue on a) By doing some unconventional connections externally on one side of theTransformer, an internal connected Dd0 transformer can be changed either to a Dd4(-120°) orDd8(+120°) connection. The same is true for internal connected Dd4 or Dd8 transformers.

(2) Group II: Example: Dd6 (180° displacement between HV and LV).

By doing some unconventional connections externally on one side of the Transformer, an internal

connected Dd6 transformer can be changed either to a Dd2(-60°) or Dd10(+60°) connection.

(3) Group III: Example: Dyn1 (-30° displacement between HV and LV).



By doing some unconventional connections externally on one side of the Transformer, an internalconnected Dyn1 transformer can be changed either to a Dyn5(-150°) or Dyn9(+90°) connection.

(4) Group IV: Example: Dyn11 (+30° displacement between HV and LV).

By doing some unconventional connections externally on one side of the Transformer, an internalconnected Dyn11 transformer can be changed either to a Dyn7(+150°) or Dyn3(-90°) connection.

Point to be remembered:

For Group-III & Group-IV: By doing some unconventional connections externally on both sidesof the Transformer, an internal connected Group-III or Group-IV transformer can be changed to

any of these two groups.Thus by doing external changes on both sides of the Transformer an internal connected Dyn1transformer can be changed to either a: Dyn3, Dyn5, Dyn7, Dyn9 or Dyn11 transformer, This isjust true for star/delta or delta/star connections.For Group-I & Group-II: Changes for delta/delta or star/star transformers between Group-I andGroup-III can just be done internally.

Why 30°phase shift occur in star-delta transformerbetween primary and secondary?

The phase shift is a natural consequence of the delta connection. The currents entering or leavingthe star winding of the transformer are in phase with the currents in the star windings. Therefore,

the currents in the delta windings are also in phase with the currents in the star windings andobviously, the three currents are 120 electrical degrees apart.But the currents entering or leaving the transformer on the delta side are formed at the point wheretwo of the windings comprising the delta come together – each of those currents is the phasor sumof the currents in the adjacent windings.When you add together two currents that are 120 electrical degrees apart, the sum is inevitablyshifted by 30 degrees.



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The Main reason for this phenomenon is that the phase voltage lags line current by30degrees.consider a delta/star transformer. The phase voltages in three phases of both primary andsecondary. you will find that in primary the phase voltage and line voltages are same, let it beVRY(take one phase).but, the corresponding secondary will have the phase voltage only in its phase

winding as it is star connected. the line voltage of star connected secondary and delta connectedprimary won’t have any phase differences between them. so this can be summarized that “thephase shift is associated with the wave forms of the three phase windings.

Why when Generating Transformer is Yd1 thanDistribution Transformer is Dy11:

This is the HV Side or the Switchyard side of the Generator Transformer is connected in Delta andthe LV Side or the generator side of the GT is connected in Star, with the Star side neutral broughtout.The LV side voltage will “lag” the HV side voltage by 30 degrees.Thus, in a generating station we create a 30 degrees lagging voltage for transmission, with respectto the generator voltage.

As we have created a 30 degrees lagging connection in the generating station, it is advisable tocreate a 30 degrees leading connection in distribution so that the user voltage is “in phase” with thegenerated voltage. And, as the transmission side is Delta and the user might need three phase, four-wire in the LV side for his single phase loads, the distribution transformer is chosen as Dyn11.

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There is magnetic coupling between HT and LT. When the load side (LT) suffers some dip the LTcurrent try to go out of phase with HT current, so 30 degree phase shift in Dyn-11 keeps the two

currents in phase when there is dip.So the vector group at the generating station is important while selecting distribution Transformer.

Vector Group in Generating-Transmission-Distribution System:

Generating TC is Yd1 transmitted power at 400KV, for 400KV to 220KV Yy is used and by usingYd between e.g. 220 and 66 kV, then Dy from 66 to 11 kV so that their phase shifts can becancelled out. And for LV (400/230V) supplies at 50 Hz are usually 3 phase, earthed neutral, so a“Dyn” LV winding is needed. Here GT side -30lag (Yd1) can be nullify +30 by using distributionTransformer of Dy11.A reason for using Yd between e.g. 220 and 66 kV, then Dy from 66 to 11 kV is that their phaseshifts can cancel out and It is then also possible to parallel a 220/11 kV YY transformer, at 11 kV,

with the 66/11 kV (a YY transformer often has a third, delta, winding to reduce harmonics). If onewent Dy11 – Dy11 from 220 to 11 kV, there would be a 60 degree shift, which is not possible in onetransformer. The “standard” transformer groups in distribution avoid that kind of limitation, as aresult of thought and experience leading to lowest cost over many years.

Generator TC is Yd1, Can we use Distribution TCDy5 instead of Dy11.

With regards to theory, there are no special advantages of Dyn11 over Dyn5.In Isolation Application: In isolated applications there is no advantage or disadvantage by usingDy5 or Dy11. If however we wish to interconnect the secondary sides of different Dny transformers,we must have compatible transformers, and that can be achieved if you have a Dyn11 among agroup of Dyn5′s and vice versa.

In Parallel Connection: Practically, the relative places of the phases remain same in Dyn11compared to Dyn5.If we use Yd1 Transformer on Generating Side and Distribution side Dy11 transformer than -30 lagof generating side (Yd1) is nullify by +30 Lead at Receiving side Dy11) so no phase differencerespect to generating Side and if we are on the HV side of the Transformer, and if we denote thephases as R- Y-B from left to right, the same phases on the LV side will be R- Y -B, but from left toRight.

This will make the Transmission lines have same color (for identification) whether it is input to or



output from the Transformer.If we use Yd1 Transformer on Generating Side and Distribution side Dy5 transformer than -30 lagof generating side (Yd1) is more lag by -150 Lag at Receiving side (Dy5) so Total phase differencerespect to generating Side is 180 deg (-30+-150=-180) and if we are on the HV side of theTransformer, and if we denote the phases as R- Y-B from left to right, the same phases on the LV

side will be R- Y -B, but from Right to Left.This will make the Transmission lines have No same color (for identification) whether it is input toor output from the Transformer.The difference in output between the Dyn11 and Dny5 and is therefore 180 degrees.

FILED UNDER UNCATEGORIZED

About Jignesh.ParmarJignesh Parmar has completed his B.E(Electrical) from Gujarat University. He has more than 11 yearsexperience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical

Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associatewith one of the leading business group as a Assistant Manager at Ahmedabad,India. He is FreelancerProgrammer of Advance Excel and design useful Excel Sheets of Electrical Engineering as perIS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India"Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. Hewants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions andupdating themselves on various Engineering Topics.

43 Responses to Vector Group of Transformer

Shantanu Joshi says:May 24, 2012 at 5:44 am

In a system of 1 grid incomer connected to Dy11 transformer and a local generator connected to

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In a system of 1 grid incomer connected to Dy11 transformer and a local generator connected toDy1 transformer is it possible to synchronise the two incomers?

Reply

Hussain Shaik says:May 24, 2012 at 11:17 amThank you so much for whatever you have, the best you are giving to us regarding the subjectTransformers. Brother Jignesh, kindly provide a bit of ” ANSI Standard Transformer ” also in briefwherever it suits for the comparison of IEC Standards.

Reply

nikhil says:May 24, 2012 at 12:11 pmSIR PLEASE INSIST ME WHAT GRASE OF TRANSFORMER OIL SHOULD BE USED FOR 5mva TRANSFORMER FOR 33 kV SUPPLY.

ReplyPriyanka says:

June 2, 2012 at 5:07 amThank you so much for this information

ReplyTapani Julin says:June 8, 2012 at 12:02 pmSix Ways to wire Star Winding is very helpful to me,Honestly i don’t know how to do it butbecause of it i learn thanks for a very good information.

ReplyByju Ramachandrn says:July 1, 2012 at 8:03 amDear Sir,

I understood that the generator transformer vector group is delta at generator side and star in yard

side. But in your article it is mentioned as reverse order. Please clarify

ReplyJignesh.Parmar says:July 1, 2012 at 10:22 amAs per IEC Vector group shown in HV winding / LV winding so i Generator transformer HVside is Transmission side and LV is Generator side.

Replyk mohana krishna says:July 5, 2012 at 6:06 pmsirIam an electrical engineer working in APTRANSCO, Sir I want to know the operation of OLTC in100 mva power transformer with tap connection. we have 25 nos of taps with 21st tap as normal if

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possible explain with sketch.

Thanking sir

K Mohana Krishna

ReplyImranullah says:June 5, 2013 at 8:01 amPlease see the Rating & Diagram plate of that (100 MVA) transformer.

Replyrehan says:July 13, 2012 at 10:00 pmwe good stuff i really liked that

ReplySUJITH C NAIR ,KANHANGAD-KERALA says:

September 15, 2012 at 11:50 amsirall the informations are 100% practical…..thank you very much sir

Replyrandy addae junior says:October 17, 2012 at 5:11 pm

I really like your diagrames and the explanations

Replyjaswant singh bhamra says:October 22, 2012 at 8:29 ami really like your diagrames and the explanationsjaswant singh bhamra senior test & commissioning sts switchgear uk

ReplyR.K.SHARMA says:October 22, 2012 at 4:34 pmInformation quite useful.Can we use YD7 in place of Yd1 generator transformer.

Reply

ram says:October 28, 2012 at 6:00 amgood job sir

ReplyMd. Anowarul Islam says:October 31, 2012 at 3:04 pm

This is a fantastic tropics. But I want to know about the test methode and voltage relation of



















This is a fantastic tropics. But I want to know about the test methode and voltage relation ofdifferent type vector group.

Replyumar says:November 4, 2012 at 4:53 pmsir what is matching factor in differential protection

ReplyRashid says:

November 6, 2012 at 5:57 amPlease give the detail procedure of vector group test with the example of.Dyn1Thanks.Rashid

ReplySANTHOSH ESWARAN POTTY says:

December 2, 2012 at 4:51 pmUse full information….

ReplyAjay Shida says:December 24, 2012 at 6:18 amT

hank you so much sir

ReplyVinoth says:January 28, 2013 at 6:21 pmNice information

ReplyMarios Moschakis says:February 24, 2013 at 12:30 amDear Jignesh,

Thank you for the interesting information about the selection of transformer’s vector group.

I would like to add another interesting point: The positive effect and other characteristics oftransformers of certain vector groups on the mitigation of voltage sags. This can be done by thepositive effect of transformers of vector group 1, 5, 7 and 11 (e.g. Dy1, Yd5 etc) on asymmetricalfaults and especially as regards one-phase-to-ground faults, which are the most frequent faults.Moreover, it can be proved that two-phase, two-phase-to-ground and three-phase faults at the oneside of such transformers give the same sag magnitude at the other side of the transformer undercommon assumptions used in short-circuit analysis. I have published a journal and a conference

paper on that effect.















Kind Regards,

Dr. Marios Moschakis, LecturerDepartment of Electrical EngineeringTechnological Educational Institute of Larissa, GREECE

ReplyM.Ali Imran says:March 7, 2013 at 12:12 pm

sir,if i have a transformer of vector group Ynd11 on generating side.how can i take a neutral on LVside?

ReplySiddavatam Nizamuddin says:March 24, 2013 at 6:40 amThis is a good ready reference regarding vector group and selection of various vector groups.I would like to ask one thing regarding distribution transformers. As you know the distributionsystem normally on HV side connected in parallel and LV side radial. That means the LV of twotransformers will never be connected in parallel. In that case, can we connect the two distributiontransformers with different vector group in parallel?

Replysachin says:May 2, 2013 at 12:49 pmDear sir,which vector group give highest secondary voltage?

ReplyBino says:May 6, 2013 at 10:37 amwhat are the advantage of star star over delta star or viceversa?

Replysachidanand kumar says:May 6, 2013 at 11:08 amThanks, To clearify my problem of vector group…transformer?

ReplyRoman says:May 6, 2013 at 7:10 pm

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Replypower transformer says:












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http://otds.co.uk/products/1/transformers



May 22, 2013 at 7:58 amI read this article and i realy appreciate your efforts.Thanks for sharing this information.This is veryhelpful for people……

Replypatomchon L says:June 4, 2013 at 4:32 amWhat ‘s the difference in diagram between the Dyn11 and Dy11

Replysunil says:June 5, 2013 at 9:38 amwe want to step up 415volts to 11000volts for tunnel work. the transformer we have is star (LV) andDelta(HV). How to give earth fault protection?

ReplyRoop Bundele says:June 17, 2013 at 8:17 pmFor Step up Transformer 415/11kV

You would normally choose Yd11 or Yd1 or Yy0 or ( Yz1 or Yz11)( depending upon if it islikely to go in parallal with other existing supply at this voltage or further after steps up/down)

instead of Dy11 or Dy1 for Earth fault Protection.

As per IEC presentation of vector Group First letter represent High voltage winding

Replyharish patel says:June 14, 2013 at 10:41 amdear sir will you explaine me formula kva=1.732*v*i*pf in which v=line voltage or phasevoltage,i=line ampere or phase ampere,because as per my knownge v= avrage line to line voltageand i= avrage phase to phase current but i am facing problem from transformer manufacturerhope you do needful to me

Replyjavad ahamad says:

June 19, 2013 at 7:55 amvery nice information,but why we are sending with 30 deg lag in generation station??what is thepoint behind lagging while sending?

ReplyJignesh.Parmar says:June 20, 2013 at 5:34 pmalready given in post

ReplyTimika Laljie says:













http://www.jiguparmar.com/





June 24, 2013 at 5:51 pmdear siram using the PSS Sincal software, and i can’t figure out which group vector represents the single

phase two winding transformer.

please help

ReplyCourtney Powell says:June 27, 2013 at 5:42 amvery helpful, thank you!

Replyrajasekaran palani says:July 23, 2013 at 2:46 pmFor a 5MVA, 0415/6.6KV, Which vector group I have to choose – Please advise

Replynatasha says:August 2, 2013 at 11:44 pmWhat are the only phase displacements in degrees with which it ispossible to parallel the secondaries of two transformers?

ReplyRags says:August 13, 2013 at 1:54 pmDoes the downstream transformer vektor groups have an effect on fault currents. This is specificallyas distance from the source and voltage levels have effect

ReplySujit Sengupta says:

August 13, 2013 at 6:03 pmGreat work Jignesh, I would like to connect with you,Sujit Sengupta,

Replyanandkumar says:August 14, 2013 at 3:16 pmI learn more subject from you thanks

Replysandeep says:August 17, 2013 at 8:40 amJignesh Sir, Thank u for good information.

In star-star transformer how can we do vector group test??



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