Answer / iamdon

Vector groups are used to indicate the phase difference
between primary and secondary quanrtity in case of 3 phase
transformers.

Application:
On the basis of vector group, we choose the transformers
which could be operated in parallel.
Two transformer belonging to same parallel group can be
paralled only.

phase difference for various group

Group 1= 0 degree.
Group 2= 180 degree.
Group 3= -30 degree.
Group 4= +30 degree.

Depending upon the applications Star,delta or ZigZag connection
is used.Also there are many possible winding pattern even for
same connection pairs(e.g. star/delta, delta/star, delta/delta,
star/star, delta/zigzag etc).So we have inherent phase
difference with respect to each other.This difference is
technically represented by different notations.

Author:arbelectbit@yahoo.com

Answer / alpesh c

hey thanks for the answer but still i am having question
that y so many groups? y to alter connections for various
group? what are the effects of such connections ? cant we
use only dy11 everywhere? is there any particular
application for each group?

Answer / gajendra pal singh

Yes vector group are used to indicate the winding connections

Answer / rakesh

To identify the HV & LV Side as well as the phase difference between primary & secondary voltage.

Answer / paul

By having multiply vector groups, you have the ability to parallel 2 or more transformers with with different vector groups by altering their connections.

EG. you can change a Yd11 into a Yd1 by changing the HV and LV phase sequence from positive to negative.

So with that in mind a Yd1 can be converted to a Yd5 if required by placing L1 onto L2, L2 onto L3 and L3 onto L1. The reason for the 4 vector group shift is down the fact that you have rotated each phase by 120 degrees

When we have earthing mesh or underground earthing network in industrial plants, weather we have NT-S or NT-C-S kind of earthing system, so eventually weather we must use 4 or 5 wire in 400 volt level (For example 3×150+70 mm2 or 5×150 mm2) in this connection I would like to know exactly the paragraph of IEC or IEEE number

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