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giri
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Join Date: May 2009
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Incomer Tripping on Differential Protection

11/28/2014 12:18 PM

Recently when we started 6.6kV,1400kW motor,the main incomer got trippped on differential protection.We could later find out the reason,which was due to leakage current in the CT secondary terminals at the front side of the panel.The incomer CT ratio: 2000/1A.But we could not pin point why this has happened now and not before when the motor was started so many times before also recently.Hope someone couldhelp me out here.

Thank you.

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SHOCKHISCAN
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Join Date: Nov 2007
Location: Eastern Arizona mountains on Route 666 about a mile from God's country
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#1

Re: Incomer tripping on differential protection

11/28/2014 5:06 PM

The CT insulation obviously failed which happens sometimes.

You did not state how long the CT has been in service.

I would make sure the voltage rating of the CT meets the application requirements.

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giri
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#2
In reply to #1

Re: Incomer tripping on differential protection

11/28/2014 10:07 PM

We have identified the problem,which was in connector from which it goes to protection relay.There was leakage current due to this faulty connector.B/w, the incomer of 6.6kV board is fed from a 33kV/6.6kV transformer.

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manindra
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#3
In reply to #2

Re: Incomer tripping on differential protection

12/01/2014 12:16 PM

In addition to the above you may also check whether 2nd. harmonic blocking filter circuit in the relay is functioning properly.

Manindra.

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