Can CBCT be Used in Restricted Earth Fault?

But, where have you located the CBCT for sensing the restricted earth fault current?

EE65, I've sent you a PM.

I take it that was the reply to my PM

For the benefit of others here's what was in the PM

It's a long time since I had any dealings with REF and the ones I dealt with all had independent phase CT's and with high impedance relays. Now I can see a CBCT being used to detect REF but with what kind of relay?

Geo. Ellison used them for outgoing feeds from their ACB panels but they used normal current relays. (Not that I was too impressed with them, I set fire to 2 ACB's in one afternoon thanks to their poor design)!*

* It was comical I radioed my mechanical counterpart and asked him to re-close one ACB as I was 150' up in the air. Reply came back "you can bu**er off, the sub's full of smoke"!

I am sorry! I should have replied your PM. But, I was not sure that you wanted a reply.

no.. if u use like that, it will be stand by earth fault protection and not REF. REF will be effective if all the three phase CT secondaries is connected in series and connected with neutral side CT secondary. Moreover most of the REF protection operates with voltage operated coil . so maybe the current you injected while testing would not have produced enough voltage across the relay coil to operate it.