To avoid short-circuit feedback current for improving current protection of asynchronous electrical motor

Three-phase short-circuit occurred to the loop of motor near-to bus or bus itself,the non-fault motors' feedback current to the short-circuit point may cause their own instantaneous overcurrent protection operate.This paper analyzes this situation from an example and solves the problem by two ways.The first way is to arrange a directional power relay of high or low current protection and the second way is to arrange a time-delay relay.