Modeling method of fast transient for unsymmetrical stray capacitance to ground.

Transient characteristic of power system apparatus in a high-frequency region should be modeled with stray capacitors. Pi-type circuit is commonly used to represent the stray capacitors between terminals and those to the ground. A modeling method for the pi-type circuit with unsymmetrical stray capacitances to ground is proposed in this paper. To obtain the unsymmetrical stray capacitances to ground, a couple of differential-mode measurements are interchangeably applied. The parameters of the pi-type circuit can be determined by the measurements with a common-mode measurement. A nonlinear least-squares method is used to estimate the capacitances. The method is applied to compose an equivalent circuit of a miniature circuit breaker (MCB), which has unsymmetrical stray capacitances to ground. The application is not only for the MCB but also for a scaled model of a high-voltage circuit breaker. A gas-filled arrester is used as a voltage sensor for the test because the voltage across the stray capacitor cannot be directly measured due to the input capacitance of a voltage probe. A transient response of the MCB with the gas-filled arresters is numerically simulated to show the usefulness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]