SIMULATION OF VOLTAGE SAG SEVERITY SOLVES MOST OF PROTECTION PROBLEMS

Based on field experience and power system simulation on electrical transient analysis program (ETAP) an idea of voltage sag aggressiveness is presented to facilitate industrial customers and power equipment manufacturers to optimize their ridethrough options. The idea of voltage sag aggressiveness appears to be of tremendous importance for industrial system designers , equipment manufacturers and utilities . The voltage sag aggressiveness has been defined as the product of % voltage sag magnitude and its duration . The findings are based on simulation results of a 70 Km long EHV network feeding to a group of large industrial users. The utility network and industrial loads were simulated for transient stability . The impact of voltage sag aggression was studied by varying durations of voltage dips and their magnitudes. The voltage dip histories of 13 large manufacturing industries were collected and their equipment sensitivities were analyzed in terms of % voltage sag magnitude and duration . Similar, voltage sag were also observed when utility network was simulated for single line to ground , phase-phase and three phase faults. However , some of the voltage sag signatures and transient mpulses recorded by customers could not be reproduced on computer using ETAP simulation program. Nevertheless, it was amazing to note that some of the sensitive equipment do trip during voltage sags of small magnitudes & long durations and others for the voltage sags of large magnitudes & small durations.

SIMULATION OF VOLTAGE SAG SEVERITY SOLVES MOST OF PROTECTION PROBLEMS Keywords:

Voltage Sag Aggressiveness( VSA) , Power Quality , Ride-Through and Voltage Dips