Transient analysis of synchronous generator with stator winding faults based on starting process

Abstract

Multi-loop theory is the most common and effective method used for analyzing stator winding internal faults of synchronous generators. Based on the current analysis methods, this paper modifies the existing models and introduces the motion equation of rotor into the multi-loop analysis model to describe the associated relations between main parameters (e.g. current, voltage, torque, speed of rotation) of generator. Since the starting process of motor contains abundant information, this paper analyzes the influence of internal faults to relevant parameters, during the starting process from zero to rated speed. Through analysis some conclusions can be obtained as follow: when stator winding internal faults occur, since the influence of space harmonic is stronger, electromagnetic torque is on oscillatory regime. All waves are distorted when turn-to-turn faults occur. The starting current is bigger than normal, and the current will fluctuate after stabilization. The changing trends of short circular current and neutral-point current are the same. The currents are both small when starting, then gradually decay and go stabilization after an obvious increasing. The amplitudes of currents are far bigger than every branch current of stator. After faults, the electromagnetic torque of motor changes a lot and there is still an oscillation with certain amplitudes after stabilization. More short turns would cause bigger amplitudes of oscillation.