Answer / maheshreddy

Purpose: The Polarity and Phase relation tests are
importent when two or more transformer are to be
paralleled.Parelleled transformer must have the same
polarity and phase relation to avoid parial or complete
short circuits.

Test Procedure:(Yyn11)
The L.V. vector will be superimposed on H.V. by connecting
1U & 2U Terminals. The three-phase voltage will be applied
to the line terminals of H.V. winding. Voltage measurement
will be done across:
1U-1V:
1V-1W:
1W-1U:

1V-2V: 1V-2W:
1W-2V: 1W-2W:
1U-2N: 1V-2N:



Checks: - 1V-2V = 1V-2W
1W-2V > 1W-2W
1U-2N + 1V-2N = 1U-1V

Answer / pavan

Vector group analysis is done to know the phase displacement.

Answer / suresh kumar

I also wanted to know this. But as per my knowledge, Same
phase of both primary and secondary are to be shorted
before applying voltage in the answer given by Mr.
Maheshreddy.
Please let me know am I correct?

Answer / gunasekaran

this is important for parallel operation vector group should
be same another one is vector group is changed polarity of
the transformer also change it YNyn0 become YNyn6 if it is
changed

Answer / r. n. aggarwal

It is conducted to ascertain the polarity and phase
displacement.

The polarity of two transformer having the same vector
group must be same.

A further check to confirm that the polarity or phase
displacement ( vector group ) of two transformer is the
same.A single three phase LT supply is fed to the HT side
of Transformers and the same phase of the LT suppy must be
connected to the corresponding HT terminals of
Transformers .Then the voltage is checked on LT terminals
of transformers with multimeter between the same phases and
it should read almost zero.

Answer / anil k panjani

I would like to know the test procedure for Dyn11 vector
group and the conditions to be met for the same

.if the vector group of two transformers is not same n tey r connected in parallel operation then what will happen?

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