Dielectric Surface Flashover under Long-Term Repetitive Microsecond Pulses in Compressed Gas Environment

As a key component of a high-power microwave (HPM) system, a multi-gap gas switch (MGS) has recently developed insulation failure due to surface flashover. Although design criteria for surface insulation have been put forward, it is still not clear how the insulation in this case deteriorated under long-term repetitive microsecond pulses (RMPs). In this paper, flashover experiments under RMPs were carried out on various dielectric surfaces between parallel-plane electrodes in SF6 and air atmospheres, respectively. Based on tests of the surface insulation lifetime (SIL), an empirical formula for SIL prediction is proposed with variations of insulator work coefficient lambda, which is a more suitable parameter to characterize SIL under RMPs. Due of the accumulation effect, the relationship between E/p and pt(delay) varies with the pulse repetitive frequency (PRF) and SIL recovery capability decreases with an increase in PRF and surface deterioration is exacerbated during successive flashovers. It is concluded that the flashover path plays a crucial role in surface insulation performance under RMPs due to the photoemission induced by ultraviolet (UV) radiation, signifying the necessity of reducing surface paths in future designs as well as the improvement of surface insulation.

Automated summary

This study conducted flashover experiments on various dielectric surfaces under RMPs and proposed an empirical formula for SIL prediction, with lambda as a more suitable parameter. It was found that the relationship between E/p and pt(delay) varies with PRF, and the SIL recovery capability decreases with an increase in PRF, exacerbating surface deterioration during successive flashovers.