Simple model for post-fault motor behaviour for reliability/power quality assessment of industrial power systems

Voltage sags are more and more being considered as a severe power quality problem. However, stochastic prediction tools for voltage sags are rare. The few methods that have been proposed assume a rectangular voltage sag. This assumption is no longer true in many industrial power systems with large induction motor loads. A simple induction motor model has been developed to describe the extra current taken by the motor during the re-acceleration after a short circuit. This model has been incorporated in the method for reliability/power quality analysis of industrial power systems, as described in a previous paper. Simulations are presented to show the influence of the post-fault voltage sag due to motor re-acceleration on the reliability/power quality of the supply. The simulations result in a table with the expected number of interruptions of plant operation for different load sensitivities