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basler electric 3 phase bus bar diff relay

basler electric 3 phase bus bar diff relay

basler electric 3 phase bus bar diff relay

(OP)
We have a switchboard with 2 feeders and a bus tie and and two basler 3 phase diff.relays protecting the switchboard.Every motor feeder has also a ct installed and all are daisy chained together.When starting a 500kw motor on 1 feeder and a bus tie closed the diff relay used trips on all phases.The relay only has a 2 cycle delay which I think is not long enough.Has anyone worked on this relay,and can help and has anyone a CT connection for this type of scheme.Thanks in advance

RE: basler electric 3 phase bus bar diff relay

The first thing that would seem to be indicated is a rolled CT polarity. Any chance that is the cause?

RE: basler electric 3 phase bus bar diff relay

First, is this a new scheme or existing scheme? I suppose an existing scheme (you are looking for the drawings of the scheme) A diff circuit is happy when the current that enters the zone equals the current leaving the zone.

Excisting scheme (was always behaving correctly):
  Faulty CT (Do mag-curve tests on CT's)
  Broken wire on the protection scheme
  Faulty relay

New installation:
  Relay (Wrong settings, faulty relay, relay not correctly wired)
  Scheme wrongly wired
  CT's (Doesn't match, wrong polarity, faulty CT)

Except for wrong settings I would suspect a faulty CT.

www.basler.com for the relays

Ralph

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