Procedure: Take the nameplate details. See from nameplate what group the transformer belongs. Suppose nameplate says that transformer belongs to Dy11.
Take the IR value between
a) HV and LV with body grounded. That is between A2 – a2, B2 – b2, C2 – c2.
b) HV and body with LV grounded and
c) LV and body with HV grounded.
Connect A2 to a2 and give low voltage (415 V) to HV side. Measure voltage between
a. C2 – b2 → 410 V (example).
b. C2 – c2 → 395 V (example).
c. B2 – b2 → 395 V (example).
d. B2 – c2 → 395 V (example).
Draw the diagram of Dy11 and check that the readings got are correct.
According to the fig
C2 c2 = B2 b2 = B2 c2.
And C2 b2 will be greater than C2 c2 , B2 b2, B2 c2.
That is C2 b2 >> C c2.
If these conditions are satisfied then that transformer belongs to vector group Dy11.
That is C2 b2 >> C c2.
If these conditions are satisfied then that transformer belongs to vector group Dy11.
For Dy1 transformer
B2 c2 will be greater than B2 b2, C2 c2, C2 b2.
That is B2 b2 >> B b2.
For Yy0 transformer
B2 c2 = C2 b2
B b2 = C c2 B b2 and C c2 will be lesser than
B2 b2 and C2 b2.
