真空中沿面闪络现象是制约真空设备耐压强度的一个重要因素,采用多层高梯度绝缘技术,比传统绝缘结构能显著提高击穿场强。介绍了该技术的研究现状,并从真空沿面闪络的二次电子崩理论入手,分析该结构对闪络过程的影响。同时,从小间隙串联的模型以及对外加电场的影响两方面,解释了多层高梯度绝缘结构可以提高绝缘性能的原因,它与公开的实验现象和结论也比较符合。

Coaxial electrodes structure is applied widely in high power pulse apparatus.Based on ANSYS software package,the influence on coaxial spatial electric potential or electric field strength is calculated as the parameters variation,such as inner electrode diameter,flashover length,and solid dielectric factor,etc.,Through comparing calculating results with simulating results,variable tendency of edge-effect of coaxial electrodes is ascertained.The effective length of the electrode is attained,in which edge-effect of coaxial electrodes doesn't interfere flashover properties on solid dielectric surface,and reference equations between the least electrode length and inner electrode diameter and flashover length in the some range of inner electrode diameter are pointed out.The simulating results can guide experimental study on flashover properties in coaxial electrodes.

It is executed to study flashover properties of polymethyl methacrylate and nylon 1010 in transformer oil in coaxial electric field by means of high voltage pulsed power supply SPG200 based on SOS switch. Flashover voltage of both solid dielectrics almost increases according to exponent following the linear growing inner electrode diameter, so do flashover voltage as well as flashover time lag versus flashover length almost linearly, polymethyl methacrylate doesn't take on higher flashover voltage than nylon 1010 in the experimental condition. Radial stress in coaxial electrodes focuses in the vicinity of inner electrode surface, as a result, flashover voltage under coaxial electric field depends on the electric intensity on the inner electrode surface and uniformity degree of radial electric field. Both increasing inner electrode diameter and prolonging flashover length can advance flash-over voltage, but increasing inner electrode diameter is more interesting.

The insulator strength of the oil-immersed equipment is usually limited by surface flashover across the oil-solid surface. At the same time, the distributions of failure strengths have some statistical characteristics. In this paper, the flashover voltage electric strengths of several PMMA test samples are measured in transformer oil under nanosecond pulse voltage. Normal distribution is introduced to describe the statistical characteristics of the experimental data. The plot of the flashover dielectric strength on Weibull paper can also demonstrates the two-parameter Weibull distribution. The parameters of the distributions are presented and the more favorable distribution is discussed with the view of obtaining consistent results for the surface dielectric strength