油纸绝缘局部放电特性和它对材料的影响

油纸绝缘局部放电的发展和它对材料的影响

王晓蓉胡龙龙张冠军严璋

西安交通大学电气工程学院，710049 西安

Partial Discharges Development in the Oil-Impregnated Pressboard

and its Effect on the Material

Wang Xiaorong Hu Longlong Zhang Guanjun Yan Zhang

School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049

摘要由于变压器结构非常复杂，不可能使内部的电场非常均匀，必然会存在有些部位局部场强强一些，因而其内部的局部放电是不可避免的。但是绝缘材料通常都有一定的耐放电特性，那么研究什么情况的放电才会对绝缘造成损坏以及不同情况下放电特性的差异，不管对于规程的制定还是对于局部放电的监测都具有重要的意义。

油浸纸板是电力变压器的主要的绝缘材料，本文借助于数字示波器和扫描电镜研究了涉及油浸纸板的局部放电的发展特性和它对绝缘纸板的影响。研究发现油浸纸板局部放电的发展过程明显的分为两个阶段：轻微放电阶段和强放电阶段。这两个放电阶段不管在放电脉冲的幅值还是在放电脉冲的形状方面都存在很明显的差别，而且中间没有明显的过渡，表现为一种突变特性。更为重要的是放电脉冲的形状与绝缘纸板的裂化有着比较直接的联系，为我们通过对局部放电的在线监测，及时发现树枝状放电的先兆提供了可能。

关键词局部放电故障监测油纸绝缘裂化Abstract Because of the complexity of transformers construction, it is impossible to make its inner electric field be homogeneous, there are some sites where their electric fields are more intense than others, and then it is unavoidable to have partial discharge (PD) in it. But usually the insulation materials can stand some extent of PD, so it is important both for the draw-up of the rules and for the diagnosis of PD to study in which condition the PD will make the insulation degradation and whether there have diversities among different PDs. The oil-impregnated pressboard is one of main insulation materials of transformer. Using digital oscilloscope and scanning electron microscope (SEM), the developing characteristics of PD pulse in the oil-impregnated pressboard and its effect were studied. It was found that there can be divided into two stages during the developing process of PD: slight discharge stage and strong discharge stage. The two stages are clearly different both from the shape and from the amplitude of the PD pulse. There has not clear transient period and shows a characteristics of sudden change between them. And it is more important that there are some direct relations between the shapes of PD pulses and the degradation of pressboard, through which it may be possible to discover the symptom of tree-like discharge in pressboard with the help of PD on-line monitor.

Keywords partial discharge fault monitor oil-impregnated pressboard degradation

1.引言

局部放电与绝缘材料的老化和击穿密切相关，进而影响高压电力设备的寿命，因此对局部放电检测和识别是保证大型电力设备安全稳定运行的有效工具之一。研究局部放电的发展过程以及对绝缘材料的影响有助于进一步认识局部放电的机理和它与绝缘材料老化的关系，进而有可能为根据测量得到的现象了解电力设备内部放电的特征和绝缘的状态提供依据。

80年代中期，国内220kV变压器围屏爬电故障时有发生，造成了巨大的经济损失。针对这一问题国内不少学者进行了比较深入的研究[1-5]，系统分析了故障的起因和现象，并提出了相应的预防措施和诊断方法。但他们分析研究的目的主要是寻找故障起因，为改进设计提供参考。即使提到一些监测和诊断的方法[4,5]，也仅是从油色谱分析方面考虑的。而色谱分析有一定的时延性，无法发现树枝状放电的先兆，当通过色谱发现放电性故障时，放电往往已经比较严重了。而围屏爬电或树枝状放电是局部放电的一种，局部放电测量的一大优点就是它对故障很灵敏，因而从