TRIPPING FOR NO FAULT
Transformer Earth fault protection was operated when load increasing.Then investigation started and team checked all power cables transformer IR value. Then primary injection test was done and found "B" phase CT secondary wire loose connection. " B" phase current not reached to relay and residual current developed. Residual current flow through neutral coil and earth fault operated during load condition only.
NO TRIPPING FOR FAULT
Transformer Earth fault protection was operated during fault condition. After investigation found the secondary wire going to neutral protection coil was ground and residual current taken essay path to return. So neutral trip coil not getting the fault residual current to trip the breaker.
