Restricted Earth fault protection active because Unbalance load of transformer

[iphapppi]

Is there any Possibilities Restricted Earth Fault Protection of Transformer active because of unbalance load,Fault on the transmission line, or other cause besides ground fault on HV side?? I'm curious because recently two of our Station Service Transformer trip simmultaneously, and both are trip because of REF protection.
Thank you for the information

 

[davidbeach]

The neutral CT wired backward? If the REF is set up correctly, the only thing it can respond to is a ground fault in the "restricted" area bounded by the CTs. Has it every been competently commissioned? That would include primary current injection to prove the CT orientation.

 

[iphapppi]

I'm not sure about the neutral CT wiring, is it correct or not. but the CT commisioning already carry out and the result is good. I'm confuse how both of our Station service transformer trip at the same time because they attached at different diameter on GIS 150 kV

 

[DTR2011]

This can generally be two things. The CT and secondary circuits or the relay settings. Both have to be in agreement. A true primary injection test will reveal if the system is operating as designed.

If you have event reports from the trips you incurred, check these, as they should also show you any CT polarities / magnitudes that are not logical. You should also check against your settings.

If you have the data, post it here for a better analysis.