which fault current is maximum: 3 phase short circuit, LG, LL or LLG?? why??

which fault current is maximum: 3 phase short circuit, LG,
LL or LLG?? why??
in one of the problems that i have solved, 3 phase short
circuit current on an unloaded generator came out to be
less than the LG fault current. can anybody please explain
why.

Question Posted / minu

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which fault current is maximum: 3 phase short circuit, LG, LL or LLG?? why?? in one of the proble..

Answer / shubham gupta

it depends upon the grounding method employed.
LG fault current is more if the generator is solidly grounded.

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which fault current is maximum: 3 phase short circuit, LG, LL or LLG?? why?? in one of the proble..

Answer / dr rajan

It is always the 3 phase bolted fault. Check your problem
again. You may have made a mistake. Why 3Ph fault current is
high?

When all phases are grounded or shorted, the impedance is just
let us say X in each phase leading to V/X x 3 times. where as
when you have LG, you will include the line impedance in
series with X, equals X+xL, which is more than X on 3Ph short
ckt. When you divide V/(X+xL) what will you have???? More
current or less current???????

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2 No

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