The magnitude of earth fault current for a given fault position within a winding demands upon the winding connections and method of neutral grounding. Earth fault protection for an electric motor is provide by instantaneous relay having a setting of approximately 30% of motor rated current in the residual circuits of two CTs and with ground wire.
Intern turn winding fault can be easily detect by differential protection relay. Also detect by buchholz relay (gas operated relay), cause buchholz relay is used to detect the internal fault of transformer.
EXAMIANS