振荡冲击电压下SF6气体中绝缘子气隙局部放电特性研究

随着GIS设备现场冲击耐压试验的推广实施,冲击电压下的局部放电检测被作为一种新方法,应用于GIS的现场绝缘诊断。冲击电压能够有效限制电晕稳定性作用,相比交流低频电压对局部极不均匀场类缺陷的发现能力更强,因此该方法将具有较好的应用前景。本文建立了冲击电压下的局部放电宽频带电脉冲检测系统,采用标准振荡雷电冲击(OLI)和标准振荡操作冲击(OSL)作为激励源,对绝缘子气隙缺陷在SF₆气体中的局部放电特性及影响因素进行了研究,并在此基础上针对预置人工绝缘气隙缺陷的实际GIS试品进行了模拟试验。研究表明：在振荡冲击下,气隙局部放电脉冲主要包括首次放电、后继放电及反向放电三种放电形式,其中首次放电对其他几种放电形式具有决定作用。且气压、背景场强及气隙尺寸比等对绝缘子气隙局部放电行为具有明显影响。GIS的模拟局部放电检测表明,两种振荡冲击电压(OLI和OSI)均能够有效检测GIS内部的气隙类缺陷。

Characteristics of Partial Discharges at Insulator Air Gap Under Oscillating Impulse Voltages in SF6 Gas

As the impulse withstanding test for GIS is widely used in field, the PD detection under impulse is considered as a new diagnosis method for insulation of GIS. Some studies and statistics showed that the impulse voltage had greater efficiencies in finding local enhanced defects comparing with AC voltages due to its limitation effect on corona stabilization. In this paper, a wideband PD detection system was built, by which the pulse current signal could be obtained. The PD behaviors and the statistical distributions were investigated under standard oscillating light impulse(OLI) and oscillating switching impulse(OSI). Based on that, an actual GIS with artificial insulator air gap defect was tested. By experiments, three PD sequences were summarized and their occurrence probabilities were found to vary with the voltage level, the gas pressure and the dimension of air gap defect. And the first discharge decides the other two partial discharge. The PD tests on actual GIS demonstrated that OLI and OSI voltages could efficiently excite PDs from insulator air gap defects in GIS.