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

Tianyu Lin,Zhijian Lu,Peng Wei,Lanjun Yang,Chengying Liu,Zhengwen Wang,Yongpeng Zhang

doi:10.3390/ma14123343

Abstract

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 λ, which is a more suitable parameter to characterize SIL under RMPs. Due of the accumulation effect, the relationship between E/p and ptdelay 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.

Highlights

A self-break repetitive multi-gap gas switch (MGS) [1], shown in Figure 1, composed of a one-trigger stage and five rimfire stages in series, was developed to meet the demands of operating at a higher voltage and a higher pulse repetitive frequency (PRF) for the high-power microwave (HPM) generator as well as having a more compact structure
Of surface insulation lifetime (SIL) among 10 measurements under the same conditions was utilized to determining the statistics, analyses, and prediction of long-term surface insulation failures
P(N) is the cumulative probability of surface insulation failure, i.e., flashover occurs. αN is the scale parameter and equals the SIL under a 63.2% flashover probability. βN is the shape parameter [18] and reflects the distribution range of the SILs: a larger βN indicates a smaller dispersion of SILs

Summary

Introduction

A self-break repetitive MGS [1], shown in Figure 1, composed of a one-trigger stage and five rimfire stages in series, was developed to meet the demands of operating at a higher voltage and a higher PRF for the HPM generator as well as having a more compact structure. A self-break repetitive MGS [1], shown, composed of a one-trigger stage and five rimfire stages in series, was developed to meet the demands of operating at a higher voltage and a higher PRF for the HPM generator as well as having a more compact structure. Rimfire stages in series were utilized to improve the breakdown voltage and the recovery capability after suffering repetitive pulses compared with the single-stage switch. The insulation capability of the stage insulators contributes to the performance of the switch. The working conditions of the MGS in the HPM generator are less than 780 kV (one rimfire stage is 130 kV) with a rise time of ~30 μs at 50 Hz in a 0.4 MPa SF6 environment

Results

Discussion

Conclusion