Propagation Properties of High-Frequency Electromagnetic Wave Through Typical In-Field GIS Structures

The safe operation of gas-insulated switchgears (GIS) is crucial for modern power systems, since the breakdown or failure of GIS equipment would cause severe interruption of the power supply and even accidents. Among the problems that would potentially harm the operation conditions of GIS apparatus, partial discharge (PD) and its subsequent electromagnetic (EM) waves serve as the essential considerations. In order to investigate the propagation property of high-frequency EM waves excited by PD in typical GIS structures, experiments and corresponding numerical simulation were conducted with convincing results presented in this paper. The spectrum analyzer working in two-port insertion loss mode was applied to capture the attenuation characteristic of the EM wave from 100 MHz to 1 GHz through three representative types of structures: the spacer, L-shaped branch, and T-shaped branch. Besides, the corresponding simulation platforms have been built and the High Frequency Structure Simulator was adopted to numerically simulate the propagation of high-frequency EM wave in GIS. The simulation results follow substantial consistency with the experimental results. Based upon these results, major causes of the EM wave attenuation have been analyzed, namely, the reflection and the mode transformation. Taking the presented EM wave propagation properties into account, the optimal placement of PD ultra-high frequency sensors for online monitoring of GIS equipment is discussed to improve the monitoring sensitivity and efficiency.