Vector Group of Transformers

To Training on Vector group groupss of of Transfor Transformer  mer  Presented By: Vinod J. Patel Electrical and I&C De

1

Introduction to Vector Group • The vector group marks the circuitry of windings and their phase position to each other. It consists of a capital and small letter plus a code number. The capital letter ! B! " refers to the #V winding and the lower case a! b! c to the $V winding with %&! %B&! %"& for a tertiary winding! where provided. 'eutral terminals precede line terminals.

Electrical and I&C De

2

Introduction to Vector Group • The vector group marks the circuitry of windings and their phase position to each other. It consists of a capital and small letter plus a code number. The capital letter ! B! " refers to the #V winding and the lower case a! b! c to the $V winding with %&! %B&! %"& for a tertiary winding! where provided. 'eutral terminals precede line terminals.

Electrical and I&C De

2

Introduction to Vector Group • (ach winding has two ends designated by the subscript numbers )! *! or if there are intermediary tapings %or there are sections of the same winding& these are numbered in order to their separation from end ). The most common vector groups are summari+ed alongside! input left,hand! output right,hand. -nless otherwise reuested. Electrical and I&C De



"e#uirement of Vector Group • In / phase transformers polarity alone is insufficient to represent the relation between #V and $V windings. In addition to the terminal marking on #V and $V side voltage vector diagram are reuired to show the angular displacement between #V and $V winding. Vector group is necessary to indicate the terminal marking and the phase displacement between primary and secondary voltages or currents. Electrical and I&C De

!

"e#uirement of Vector Group %nder normal condition te line to line 'oltages on (V side are displaced from corresponding 'oltages on )V sides. *lso line to neutral 'oltage on (V side are displaced from corresponding 'oltages on )V side. Te displacement depend upon te transformer connections. *s per IS 2+21/2, tere are four 'ector groups of standard connections Electrical and I&C De

$

Phase shifts in 0tar 1elta Transformers • Positive 2 'egative phase seuence voltages and currents undergo a phase shift in passing through a star,delta transformer which depends on labeling of terminals. • Before considering the phase shift! we need to discuss the standard polarity marking of a single phase transformer as shown in the figure,). The transformer ends marked with a dot have the same polarity. Therefore! voltage V##3 is in phase with voltage V$$3. Electrical and I&C De



0olarit ar3ing of a single pase transformer

Electrical and I&C De

/

Phase shifts in 0tar 1elta Transformers • "onsider now a star4delta transformer with terminal labeling as indicated in 5igure,*. 6indings shown parallel to each other are magnetically coupled. ssume that the transformer is e7cited with positive seuence voltages and carries positive seuence currents. 6ith the polarity mark shown! we can immediately draw the phasor diagram of 5igure,/. Electrical and I&C De

4

Phase shifts in 0tar 1elta Transformers • The following relatdionship between the voltages on two sides of the transformer is observed from the phasor diagram. Positive seuence line voltages on star side lead the corresponding voltages on the delta side by /8 deg. The same also applies for the line currents. Electrical and I&C De



Star Delta Transformation

Electrical and I&C De

1+

0asor diagram of star-delta Transformer 

Electrical and I&C De

11

Star Delta Transformation • If the delta side is connected as shown in 5igure,9 the phase shift reverses the delta side uantities lead the star side uantity by /8 deg.

Electrical and I&C De

12

Star Delta Transformation • Instead if the transformer of 5igure,* is now e7cited by negative phase seuence voltages 2 currents! the voltage phasor diagram will be as shown in 5igure,;.

Electrical and I&C De

1

Star Delta Transformation • The phase shift in comparison to positive seuence case now reverses! i.e. the star side uantities lag the delta side uantities by /8 deg. The result for figure, 9 also correspondingly reverses.

Electrical and I&C De

1!

Star Delta Transformation • It is assumed that a star4delta transformer is so labeled that the positive seuence uantities on the #V side lead their corresponding positive seuence uantities on the $V side by /8 deg. The reverse is the case of negative seuence uantities wherein #V uantities lag the corresponding $V uantities by /8 deg. Electrical and I&C De

1$

Star Delta Transformation • The interconnection of the phase windings to give a three phase! three,or four wire supply provides three alternative modes of connection %)& oined to give neutral and )! B) and ") may be used as line terminals. Electrical and I&C De

1

Star Delta Transformation • 0ince primary and secondary can be treated in either of these ways! at least twelve methods of connection are possible. These are arranged in four main groups! as given below! according to the phase displacement which e7ists between the line voltages on the two sides of the transformer.

Electrical and I&C De

1/

Vector Groups 5Group-16 •

?roup ): =ero phase displacement %@y8! 1d8! 1+8&

)& @y8: 0tar A 0tar "onnection *& 1d8: 1elta A 1elta "onnection /& 1+8: 1elta A =ig,+ag "onnection

Electrical and I&C De

14

7+8 Star 9 Star Connection

Electrical and I&C De

1

Dd+8 Delta 9 Delta Connection

Electrical and I&C De

2+

D:+8 Delta 9 ;ig-:ag Connection

Electrical and I&C De

21

Vector Groups 5Group-26 •

?roup *: )8 degree phase displacement %@yC! 1dC! 1+C&

)& @yC: 0tar A 0tar "onnection *& 1dC: 1elta A 1elta "onnection /& 1+C: 1elta A =ig,+ag "onnection

Electrical and I&C De

22

78 Star 9 Star Connection

Electrical and I&C De

2

Dd8 Delta 9 Delta Connection

Electrical and I&C De

2!

D:8 Delta 9 ;ig-:ag Connection

Electrical and I&C De

2$

Vector Groups 5Group-6 •

?roup /: /8 degree lag phase displacement %1y)! @d)! @+)&

)& 1y): 1elta A 0tar "onnection *& @d): 0tar A 1elta "onnection /& @+): 0tar A =ig,+ag "onnection

Electrical and I&C De

2

D18 Delta 9 Star Connection

Electrical and I&C De

2/

7d18 Star 9 Delta Connection

Electrical and I&C De

24

7:18 Star 9 ;ig-:ag Connection

Electrical and I&C De

2

Vector Groups 5Group-!6 •

?roup 9: /8 degree lead phase displacement %1y))! @d))! @+))&

)& 1y)): 1elta A 0tar "onnection *& @d)): 0tar A 1elta "onnection /& @+)): 0tar A =ig,+ag "onnection

Electrical and I&C De

+

D118 Delta 9 Star Connection

Electrical and I&C De

1

7d118 Star 9 Delta Connection

Electrical and I&C De

2

7:118 Star 9 ;ig-:ag Connection

Electrical and I&C De



Sm