Fault current discrimination during induction motor starting

摘要

Induction motors draw a very high current during starting. Over-current relays designated to protect the motors have to accurately discriminate between the starting current and high current occuring during terminal faults. Several techniques have been used for this purpose ranging from simple time delay in relay actuation to AI techniques like neural networks. The main parameters used for discrimination are the amplitude and phase angle of the fundamental component of the current. This paper presents a simulation study of the induction motor starting phenomenon investigating the behaviour of the fundamental component of the current with and without fault. The processing of the current signal involves removing the decaying DC component and estimating the ampitude and phase of the fundamental component of current. The behaviour of the current has been studied using algorithms suitable for implementation on a digital processor platform.