Answer / akhilesh singh

Due to 60deg phasor diff., PD of two secondaries will
arise. Therefor a circulating current between these two
secondary flows which causes shortcircuiting.

Answer / dubai

I agree with murali.

Transformer having -30˚ angle (here DYn 11) can be
paralleled with +30˚ (here DYn 1) angle by reversing the
phase sequence of both primary & secondary terminals of one
of the transformers eliminating phase angle errors.

Answer / murali

my referance is from jpthomson transfromers
wht ur referance my friend ?

Answer / mrudang

becuase of wrong clock number there is phase difference
and because of phase angle difference it shows negative
sequence

Answer / thatharao

Both the terminals will reverse and Phase displacement will
be zero.So phase angle will be zero.

Answer / ramniveth

dear Murali
my reference is from oxford university from book
name "Automated Technology for verification and analysis"
"http://books.google.co.in/books?
id=LbfOjdII174C&pg=PA111&dq=transformers+oxford+university#P
PA111,M1"

Answer / murali

here phase difference between to secondaries will be 60deg
transformers belonging to dy1 could be operated in parallel
with those of dy11 or viceversa by transposing two of
external high voltage connections of one of the
transformers and also corresponding low voltage external
connections .it is not necessary to change any internal
connections

Answer / ramniveth and subuhani

same pottential of two neutral cannot be earthed .because
it give rise to third harmonics.so it cannot be paralleled

Answer / rishi

delta connected HV winding,star connected LV winding with
neutral brought out,LV IS leading HV with 30degree.

in transformers for ex. 100mva and 400kv the secondary current is about 420 amps but for selection of bushing the capacity of selected bushing is 2000A why there is such big difference ?

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