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Restricted Earthfault tripping

Restricted Earthfault tripping

Restricted Earthfault tripping

(OP)
please can someone explain why the REF relay on meant to protect a 60MVA 132/33KV transformer will trip whenever a 33kv line feeding from the transformer trips on Earth fault.

RE: Restricted Earthfault tripping

CT polarity or ratio problem.

RE: Restricted Earthfault tripping

What stevenal said.

RE: Restricted Earthfault tripping

Reversed neutral CT.

RE: Restricted Earthfault tripping

Less likely, but it could be due to a blue box if you don't keep up with manufacturer notifications on firmware updates.

RE: Restricted Earthfault tripping

(OP)
Thank you all i am going back to site to look at the polarity, will update u

RE: Restricted Earthfault tripping

CT connection/polarity problem
Usually neutral CT, as ScottyUK said.

of course possible setting mistake.

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