Discriminatory Protection Analysis of Three-Phase Asynchronous Motors During Power Disturbances.

The ride through voltage disturbance of an induction motor (IM) reduces the unscheduled shutdown from processes, and the discriminatory protection allows industries to save time, protect machines and to increase the mean time before breakdown. This paper discusses the analyses of the stability performance of an induction motor under disturbance from voltage sags and short interruptions. The work also addresses the challenge associated with the operation of induction motors of power rating from 3 to 100 kW, during voltage dips, brief interruptions, transient overcurrent, and how to select the induction motors protection for a maximum operating time under such circumstances. The study aims to look for the corrected delay time and peak transient of stator current that protection scheme can handle. It is found that the rising stator current during a voltage disturbance (due to voltage sag and short interruption) can reach the per unit value of stator current up to 18 times, and it is recommended that the delay time should be settled between 100 and 200 msec. Therefore, this study is of great significance to the manufacturing industry where IMs are commonly used as it can avoid damage to the motor. [ABSTRACT FROM AUTHOR]