Apologies the actual time delay is 0.5s and it is also the same for the downstream breaker. Is it possible that the inrush can last that long. My thinking is that it should have substantially decayed after 0.1 s.
I have the curve from the manufacturers for one of the transformers. It indicates...
Thank you for the valuable information. There is no instantaneous setting on the relay. The relay is set to definite time with a 0.1 s time delay. Interestingly one of the downstream breakers also tripped on earth fault at the same time. I noticed that the time delay was set the same on both...
In the case of energisation of multiple transformers fed from a single board the main circuit breaker tripped on earth fault. The earth fault measurement is via residual current measurement. I assume that the CTs saturated and that caused the residual current to appear. The main breaker...