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 A_{2} – a_{2}, B_{2} – b_{2}, C_{2} – c_{2}.

b) HV and body with LV grounded and

c) LV and body with HV grounded.

Connect A_{2} to a_{2} and give low voltage (415 V) to HV side. Measure voltage between

a. C_{2} – b_{2} → 410 V (example).

b. C_{2} – c_{2} → 395 V (example).

c. B_{2} – b_{2} → 395 V (example).

d. B_{2} – c_{2} → 395 V (example).

Draw the diagram of Dy11 and check that the readings got are correct.

According to the fig

C_{2} c_{2 }= B_{2} b_{2} = B_{2} c_{2}.

And C_{2} b_{2} will be greater than C_{2} c_{2} , B_{2} b_{2}, B_{2} c_{2}.

That is C_{2 }b_{2} >> C c_{2}.

If these conditions are satisfied then that transformer belongs to vector group Dy11.

That is C_{2} b_{2} >> C c_{2}.

If these conditions are satisfied then that transformer belongs to vector group Dy11.

For Dy1 transformer

B_{2} c_{2} will be greater than B_{2} b_{2}, C_{2} c_{2}, C_{2} b_{2}.

That is B_{2} b_{2} >> B b_{2}.

For Yy0 transformer

B_{2} c_{2} = C_{2} b_{2}

B b_{2} = C c_{2} B b_{2} and C c_{2} will be lesser than

B_{2} b_{2} and C_{2} b_{2}.