An ATP/EMTP model for the study of both normal and abnormal substation equipment operation

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In electric utility, overcurrent and overvoltage transients in switching operations often cause severe damage on the power system equipments. In this study, Alternative Transients Program -Electromagnetic Transients Program (ATP-EMTP) was employed for a general utility system modeling. A certain 161 kV: 34.5 kV Ameren UE substation in the Potosi area was discussed. The system consisting of the generators, the transformers, the switches, a circuit breaker, a capacitor bank, a fuse holder, the transmission lines, the cables and the loads is modeled by means of provided measured data. Some non-ideal components are modeled and explained in detail in order to explain some possible complex transient behavior including inrush current, harmonic resonance, ferroresonance, reignition of the circuit breaker and other high frequency resonance effects. In the particular system, failure of a 4.5 MVAR capacitor bank happened due to an improper switching operation. The simulation results for the capacitor bank phase currents and voltages suggest that excessive switching transients due to inrush current, associated with energizing an idle transformer; oscillatory transients involving the transformer and cable parasitic capacitances upon closure of the circuit breaker; and reignition associated with a wrong circuit breaker closing followed by the opening command by protections may play a role in the failure of the fuse holder and capacitor bank.