Analytical Study of Voltage Magnification Transients Due to Capacitor Switching

This paper addresses the voltage magnification phenomena at the terminals of customer transformers due to switching the medium-voltage utility capacitors. The traditional approach to understanding the voltage magnification phenomena is analyzed and its drawbacks are shown. The closed-form expressions for the magnified transient voltage waveforms are derived. The simulation results using the analytical expressions were found to be in very good agreement with those obtained using the Electromagnetic Transients Program. Novel relationships between the network parameters corresponding to maximal peak values of the overvoltages are developed. A simple procedure for evaluation of the maximum magnified overvoltages is presented. The developed procedure has been applied in a real-world power utility. The envelope of maximum expected overvoltages on the secondary side of the customer transformers has been obtained. The customer transformers, wherein the magnified overvoltages may exceed the permissible level, have been found.