Answer / suresh kumar

the answer of Mr. RVG is correct. But I would like to
correct the question itself. Distribution transformer
converts voltage from 33KV to 400V, not 400V to 33KV.

Answer / engr. abdul barek, electrical

We use in star connection in seconday connection becouse
need neutal point in load sied( some load supply need 3
phase and some need single phase)but it is remember that
only star connection use in distrubution side transformer.

Answer / rvg

Star connection having multiple option of voltages, and
availability of neutral point makes useful for earth fault
relay operation.

Delta connection having requirement of 3 conductors and
itself is long distance, with less current and higher
voltage. So economical way is delta at high voltage side
and star at low/ or consumer end.

Answer / r m koloi

we dont need nuetral at primary side but it is needed at
sec. side because some loads of 3 ph and single phase loads
required nuetral.

Answer / pankaj malhotra

For distribution transformers, loads are connected to
secondry side. hence, requirement of neutral can be
obtained by connecting secondry of the transformer in star.
Secondly, to reduce or minimise the third harmonics in the
transformers, primary side connection generally done in
delta.

Answer / nitin palaskar

we should use delta connection in primary and star to
secondary because in delta line voltage = pphase voltage
and instar line voltage = 1.732phase voltage hence we get
173.2% more voltage hence we use delta star transformer.

Answer / siva

in secondary side there is a chance for single phase load,
three phase load, if its single phase load added more there
is a chance for unequal voltage in each phases. here we
need one neutral point that is refered as a reference
potential for load equalise the phase voltages

Answer / gangadhar

Primary function of Distribution Transformer is to step-
down 33kv into 440v..while designing the transformer we
have to consider conductor size also...in delta side line
current=1.732 times phase current and in star side phase
current=line current...as we know current is directly
proportional to cross-section of the conductor..keeping in
mind about the cost factor of conductor on load side they
prefer star connection on load side..Guys i tried to
explain in different way..i agree with above answers
also

Answer / swayanjit

WE USE DELTA CONNECTION AT PRIMARY AND STAR CONNECTION AT
SECONDARY IN CASE IF STEP UP OF VOLTAGE REQUIREMENT BECAUSE
IN DELTA/STAR TRANSFORMER THE OUT PUT VOLTAGE WILL BE 1.413
TIMES HIGHER THAN THE PHASE VOLTAGE EVEN WHEN BOTH HAVING
SAME NUMBER OF TURN. SO THE SECONDARY WILL REQUIRE LESS
INSULATION.

Answer / raj

I agree to Suresh Kumar

IT IS SAID THAT THE OLTC OPERATION SHOULD NOT BE PERFORMED WHEN THE TRANSFORMER IS GENERATION TRANSFOREMR/STEP UP MODE. WHY IS IT SO?

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