Comprehensive Simulation Research on Microprocess and Macroscopic Electromagnetic Signals of Surface Discharge in SF₆

The surface discharge on the dielectric is a common type of partial discharge (PD) in gas-insulated switchgear (GIS), but the microscopic development process of surface discharge in SF6 is unclear. To find out the microprocess of surface discharge and its correlation mechanism with the PD detection signals of GIS, the fluid-chemical simulation model of the streamer is used to simulate the microprocess of surface discharge in SF6. Then, the current signal obtained by the microprocess simulation is used as the excitation to simulate the electromagnetic signals based on the finite-integration time-domain (FITD) method. A close connection between the microscopic discharge and the macroscopic signals is established. The results show that the electron concentration at the streamer head and the streamer velocity decrease first and∫then increase during the discharge, with an average velocity of about9.84× 10^5m/s. The discharge current reached a peak value of about 0.22 A when the surface streamer reaches the cathode. In terms of waveform correlation, the absolute value of the average correlation coefficient between the electric field signals simulated in this article and the actual measured signals is above 0.7, which is much higher than the simulated signal excited by the Gaussian source. By changing the applied voltage and comparing with the experiment results, it is found that the simulation method in this article can reflect the change of signals under the influence of external conditions. As the applied voltage rises, the amplitude of the electric field signals increases, and the main frequency component on the frequency spectrum grows, with the main frequency value at about 1.2 GHz. The research in this article is an effective supplement to the existing study on the microscopic mechanism of partial discharge signals.