A Contribution to the Frequency and Transient Analysis of High Voltage Bushings

Abstract

The paper suggests a method for determining the frequency characteristics and transient response of capacitively graded high voltage bushings. It is based on an s-domain circuit model that describes the grading conducting foils and the insulating layers. In most cases, they are of different axial lengths. A system of simultaneous differential and algebraic equations is derived taking these differences into account. Its closed-form solution, subject to the boundary conditions, can be directly obtained in terms of parametric functions for the voltages and currents. They include both the location of the considered point and the Laplace operator s as independent variables. These expressions are used in order to identify the frequency dependence of the bushing’s input impedance as well as the types and frequencies of the different resonances. The expressions are numerically inverted into the time domain to get the voltage and current distributions. The technique is applied to different case studies demonstrating the effect of the wave shape of the source that initiates the transient and the termination of the central conductor.

Keywords: Frequency characteristics, electromagnetic transient analysis, GIS (gas-insulated switchgear), capacitively graded bushings, VFTOs (very fast transient overvoltages), non-uniform lines, parametric functions, differential equations, numerical Laplace inversion, condition monitoring.

Cite this Article

Saied Mohamed M. A Contribution to the Frequency and Transient Analysis of High Voltage Bushings. Journal of Power Electronics & Power Systems. 2019; 9(1): 15–26p.