LAs in differntial zone
LAs in differntial zone
(OP)
What do I need to consider when LAs are in a transformer differential zone in terms of protection settings? Or should everything be done to avoid this?
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RE: LAs in differntial zone
RE: LAs in differntial zone
Reason I ask because I see many cases where the transformer's own CTs are used for differential (basing my values off that) while the breaker to breaker zones are protected separately. And yes- that would be a belief. You won't believe how many older stations simply have a disconnect from the bus going right to the transformer putting the LAs in the buss zone.
RE: LAs in differntial zone
We have used the breaker to breaker differential protection for the transformers and the lightning arrestors (LA) in the differential zone. As such steady state of an arrestor is in terms of milli amps. Thus the relay is not sensitive to this leakage current.
When the discharge, it is active for few microseconds only. That means we are talking about the voltage/current burst for the period of microseconds which when converted to frequency it will be in MHz. These CTs are not sensitive to pick up such bursts. Hence such practice is quite safe.
RE: LAs in differntial zone