What is the minimum setting in REF relay because i am
facing some problem whenever power resumes after power
failure my transformer is tripping because of REF trip. I
am using CSPC make numerical relay(DIP switches). Now
setting is 15 percentage. What is the reason for this
triping. I sm waiting for answer
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Answer Posted / k.prakashchandra
Your setting is 15% of In.While charging ,Tr draws initial
magnetizing current 6 to 15 times the In. Any difference in
measurements by CT s at this current ,may exceed the set
current.Even 1% error in measurement at normal current
becomes 15% of In at initial charging current at 15 times
the In
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