basler electric 3 phase bus bar diff relay

alanmitchell · Apr 28, 2004

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

JJHorak · May 20, 2004

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

RalphChristie · Jun 2, 2004

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.

http://www.basler.com

for the relays

Ralph

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basler electric 3 phase bus bar diff relay

alanmitchell

Electrical

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JJHorak

Electrical

RalphChristie

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