并联运行电动机短路故障仿真及保护对策

Short-circuit simulation and protection scheme of parallel running motors

2台并联运行的异步电动机,当一台电动机发生三相或两相短路故障被电流速断保护装置切除时,会引起另外一台正常运行的电动机电流增大,超过其额定电流4倍以上,导致正常运行电动机的速断保护误动作而跳闸。基于Matlab建立2台异步电动机并联运行时短路故障的仿真模型,研究分析了产生上述情况的机理、不同类型故障的影响程度及故障信号特征,并提出了带方向元件的电流速断保护的新方案,该方案既防止了正常运行电动机电流速断保护的误动作,又不影响故障电动机电流速断保护的正确动作。动模试验证明了该方法的正确性。

When two-phase or three-phase short-circuit fault occurs in one of two parallel running asynchronous motors,it will be tripped by its instantaneous trip current protection,which results in the current increase of the normal motor,exceeding the rated current over four times,and the trip of normal motor by the misoperation of its instantaneous trip current protection. A short- circuit simulation model of two parallel running motors is established with Matlab,based on which the operation mechanism,influence degree and signal characteristics for different faults are studied,and a new scheme with directional element for instantaneous trip current protection is proposed. It guarantees the proper operation of the protection for faulty motor and prevents the misoperation of the protection for the normal motor. Tests verify its correctness.