Voltage sag source location in power systems

Abstract

This report documents a comprehensive study of available methods for locating voltage sag sources in power systems. The performance of four sag source location methods is analyzed by simulating faults in a Brazilian transmission network using PSCAD/EMTDC. The most reliable methods (distance relay, reactive power and slope of system trajectory) were then applied to a case study on a Zambian utilityindustrial customer interface to assess the vulnerability of one of the latter’s critical induction motors to voltage sags. It is shown that the sensitive load at Indeni is vulnerable to voltage sags arising from faults in both the CEC and Zesco networks, the two utilities that handle power before it gets to the customer. Further laboratory measurements were done on the analogue network model to assess the applicability of these methods to real networks. Particularly the distance relay method which showed very good performance in PSCAD/EMTDC simulations. Results indicate that the distance relay method is suitable for application to real networks as it showed correct sag source indications in both simulations and measurements. The performance of the reactive power and slope of system trajectory methods were above 90%.