Voltage sag is a significant problem that affects the quality of power, and some researches have been performed on this theme. The characteristic of load is an important factor affecting the voltage sag, which is rarely studied. This paper investigates the influence of dynamic characteristics of induction motor on voltage sag caused by short circuit fault. The analytic expression of induction electromotive force is derived by space vector method. The mechanism of amplitude and waveform changes caused by dynamic load characteristics of induction motor are analyzed. The results indicate that the voltage at the load terminal of the induction motor is higher than that at the static load during the sag. Besides, the voltage sag waveform is not in rectangular shape. The static load terminal voltage returns to normal value quickly, while the voltage at the load terminal of the induction motor needs about 200 ms after the fault is removed. Induction motors can reduce the magnitude of voltage sags caused by short circuit faults, but will extend the duration. At the same time, the bigger the induction motor capacity is, the longer the voltage recovery time after sag is.

中文翻译：

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感应电动机动态特性对短路故障电压暂降的影响

电压暂降是影响电能质量的一个重大问题，已有一些研究围绕这一主题展开。负载特性是影响电压暂降的重要因素，研究较少。本文研究了感应电动机的动态特性对短路故障引起的电压暂降的影响。利用空间矢量法推导出感应电动势的解析表达式。分析了感应电动机动态负载特性引起幅值和波形变化的机理。结果表明，在下垂期间，感应电机负载端的电压高于静负载时的电压。此外，电压暂降波形不是矩形的。静负载端电压迅速恢复正常值，而感应电机负载端的电压在故障排除后大约需要200ms。感应电动机可以减少短路故障引起的电压骤降幅度，但会延长持续时间。同时，感应电机容量越大，暂降后的电压恢复时间越长。