In a 11kv/433v transformer,at the LT side ie 433 V side why do we need to put 3

In a 11kv/433v transformer,at the LT side ie 433 V side why
do we need to put 3.5 core Cable upto Panel.The full load
rated Amps is 666 at LV side.What value of current will flow
through the Nuetral Conductor.Why can't we use 4Core Cable
instea of that?

Question Posted / raghavendran

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In a 11kv/433v transformer,at the LT side ie 433 V side why do we need to put 3.5 core Cable upto P..

Answer / hanmanth reddy y

In a three phase system with star connected secondary
(433V side) if two phases are fully loaded to 666A and the
third phase not at all loaded the current through nuetral
conductor will be 666A. But in practice in a three phase
system that the third phase not having any load and other
two phases fully loaded is not in practice. If all the
three phases loaded equally no current flows through
nuetral and nuetral cable is not required.

Based on the requirment of transformer insulation nuetral
earthing has to be done at the transformer terminal only.

Nuetral is neccessary for single phase loads. If the
nuetral is dispensed entirely it is not possible to supply
power to single phase loads. Normally even in worst case as
huelistic judgement the nutral current will not exceed 50%
of phase current under unbalaced load conditions. Hence it
is appropriate to select cable of 3.5 core rather that of a
4 core cable.

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In a 11kv/433v transformer,at the LT side ie 433 V side why do we need to put 3.5 core Cable upto P..

Answer / s.banik

we are always try to be distribute our load as balance
condition(i think transformer secondary side is star
connected),but in practical this not possible at
site.So,little current is flows through the neutral
conductor but this is not so high.some time we are use in
4core, this is depend on load condition & practical operation.

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