Computation and Analysis of Electric Field Distribution Under Lightning Impulse Voltage for 1000-kV Gas-Insulated-Switchgear Spacer

Abstract

The electric field distribution is critical to the insulation structure design of 1000-kV gas-insulated-switchgear (GIS) equipment. At present, it is not difficult to obtain the electric field distribution under commercial frequency sinusoidal voltage; however, for lightning impulse voltage, the electric field distribution is commonly substituted by electrostatic analysis under the peak voltage. As a result, this treatment may not embody the characteristics of the dielectric constant changing with frequency. In this paper, a frequency-domain mathematical model for transient analysis is established. The measured broadband frequency dielectric spectrum for the medium of a GIS spacer is well fitted by a H–N function model with three relaxation peaks. The transient analysis for a 1000-kV GIS spacer is realized by superposing the responses to the sinusoidal and direct current components of the lightning impulse waveform. The potential and electric field regulation for a 1000-kV GIS spacer under lightning impulse voltage is presented and analyzed. Furthermore, the computed results from traditional electrostatic analysis are introduced for comparison. The results indicate that the electrostatic analysis increases the computed electric field strength at the surface of the GIS spacer, while it decreases that at the interface between the GIS spacer and center conductor. It could provide computational support for the insulation structure design of 1000-kV GIS spacers.