TECHNICAL PRESENTATION

ON

VECTOR GROUP

By M M V RAVINDRA

Contents1. Polarity2. Three Phase Connections3. Vector group4. Verification of Vector Group5. Importance of Vector Group

1. Polarity The primary and

secondary windings on the core are in same phase

If the windings of the Transformer have same direction then voltage induced in both the coils are in same polarity(Additive polarity).

If two coils have opposite winding direction then Voltage induced in both coil are in opposite direction.

2. Three Phase Connections2.1 Star Connection Each end of coil with same

polarity is connected to a point called star point.

Star point may or may not be grounded

Represented with symbol “Y” in vector group

2. Three Phase Connections2.2 Delta connection Polarity end of one coil is

connected with non polarity end of another coil.

In the delta physically the neutral point does not exist so it cannot be brought out. The delta side neutral is the imaginary point 'n' (geometrically found) which is equidistant from a2, b2 and c2.

Represented with symbol “D” in vector group

2. Three Phase Connections

Zigzag connection is also called the interconnected star connection. This connection has some of the features of the Y and the ∆ connections, combining the advantages of both.

Represented with symbol “Z” in vector group

2.3 Zigzag connection

3. Vector group Vector Groups are method of categorizing the

primary and secondary winding configurations of 3-phase transformers and the phase relation between primary and secondary.

In vector group primary winding connection should be shown in capital letter

Followed by next high voltage winding connection in small letters

Followed by phase relation of secondary w.r.t primary winding in clock notation

Followed by next high voltage and its phase relation with primary winding and so on….

Ex : YNd11 For Auto Transformers connection symbol

should followed by symbol a0 Ex : YNa0 Clock notation of phase shift1. Digit 0 =0° that the LV phasor is in phase

with the HV phasor2. Digit 1 =30° lagging (LV lags HV with 30°)

because rotation is anti-clockwise.3. Digit 6 = 180° lagging (LV lags HV with

180°)

4. Digit 5 = 150° lagging (LV lags HV with 150°)

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

Examples:1.Dy112.YNd11d113.YNa0d114.Yyn0 5.Dz0

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

210 lag or 150 lead Yd7 Dy7 Yz7

240 lag or 120 lead Dd8 Dz8

300 lag or 60 lead Dd10 Dz10

330 lag or 30 lead Yd11 Dy11 Yz11

Yy0

Yy6

Yd11

Yd1

Dz0

What is the vector symbol for the below connection?

Yd5

What is the connection for the vector symbol Dy11?

4. Verification of Vector Group

5. Importance of Vector group 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 then phase difference exists between the secondary of the transformers and large circulating current flows between the two transformers.

THANK YOU