why middle phase should used for earth fault and other phases used for over cu

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why middle phase should used for earth fault and other
phases used for over current in overcurrent and earth fault
relay?

Question Posted / cheepuru_srinivas

7 Answers
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why middle phase should used for earth fault and other phases used for over current in overcurrent..

Answer / prasun bhaumik

It is a convention there will not be any problem
technically if we change that arrangement

Is This Answer Correct ?

7 Yes

4 No

why middle phase should used for earth fault and other phases used for over current in overcurrent..

Answer / vishal ingle

Not necessary to use only the middle phase.
our Back up protection cosist of two overcurrent elements
and one earth fault element.
under normal condition vector (IR + IY + IB) = 0
in fact middle phase is not used for earth fault prot.
Earth fault relay is connected between the star point of
all three phases (after O/C Relay) and the earth. if any
unbalance occurs, the unbalance current will flow through
the e/f relay.

Is This Answer Correct ?

1 Yes

1 No

why middle phase should used for earth fault and other phases used for over current in overcurrent..

Answer / gunasekaran

on that point resiudual current is zero normally current sum
is zero at thatt point whenever balance is distrubed current
will flow

Is This Answer Correct ?

2 Yes

3 No

why middle phase should used for earth fault and other phases used for over current in overcurrent..

Answer / j.dev singh

for balancing of two phases current in relay.