Study on Insulation Characteristics of GIS under Combined Voltage of DC and Lightning Impulse
Study on Insulation Characteristics of GIS under Combined Voltage of DC and Lightning Impulse
复制标题
DOI：
10.1109/tdei.2017.006535
复制
发表时间：
2017-04-01
影响因子：
3.1
通讯作者：
Gao, Chao
中科院分区：
文献类型：
--
作者：
Ma, Jingtan;Zhang, Qiaogen;Gao, Chao
运行经验表明，隔离开关分闸后，GIS母线上仍有较长时间的直流残余电压。这种直流电压不仅会引起绝缘子表面电荷和污物的积累，而且容易引起SF6气隙中游离金属颗粒的运动，削弱GIS的绝缘能力。在隔离开关重合闸时，母线上会产生冲击电压，冲击直流电压。因此，GIS将承受直流和冲击的联合电压。对GIS在直流和雷电冲击复合电压作用下的绝缘特性进行了实验研究。研究发现，对于非污秽绝缘子，当直流电压和低压电压极性相同时，组合电压下的闪络电压与单独低压下的闪络电压几乎相同。然而，当它们具有相反极性时，闪络电压随着直流电压的增加而减小。当绝缘子周围有金属颗粒或粉末时，预加直流电压会使污秽物附着在绝缘子表面，从而降低闪络电压。特别是对于颗粒污秽绝缘子，直流电压引起的表面电荷积累对闪络电压有较大影响，且直流电压与绝缘子表面电压极性相反时影响最大。此外，还研究了含自由金属颗粒的SF6气体间隙的击穿特性。研究发现，在预加直流电压作用下，颗粒会做直立运动或弹跳运动。当粒子作静止运动时，击穿电压最低。试验结果表明，GIS中的残余直流电压会使GIS的绝缘性能恶化，直流和冲击的组合电压是GIS绝缘的临界条件。此外，组合电压被证明是更敏感的检测在GIS中的一些绝缘缺陷比单独施加脉冲电压，特别是对于自由的金属颗粒，这是常见的在GIS中，但到目前为止没有提出有效的检测方法。因此，可以考虑采用直流和冲击组合电压作为GIS现场试验的补充。
Operating experience shows that residual DC voltage remains in GIS bus bar for a long time after opening of disconnectors. This DC voltage will not only cause accumulation of charges and contaminants on the insulator surface, but will also easily lead to motion of free metallic particles in SF6 gas gap, weakening the insulation ability of GIS. At the time of disconnectors reclosing, impulse voltage could be generated in the bus bar and superimpose on the pre-existing DC voltage. As a result, GIS will be under combined voltage of DC and impulse. This paper experimentally studies the insulation characteristics of GIS under combined voltage of DC and lightning impulse. It is found that, for non-contaminated insulators, when DC and LI voltage are of the same polarity, flashover voltage under combined voltage is nearly the same as the flashover voltage under LI alone. However, when they are of the opposite polarity, flashover voltage decreases with increasing DC voltage. In cases there are metallic particle or powder around insulator, pre-stressed DC voltage will cause adhesion of contaminants on the insulator surface and lead to decrease of flashover voltage. Specially, for the particle-contaminated insulator, it is found that the surface charge accumulation caused by DC voltage will have big influence on the flashover voltage, and the most critical condition is when DC and LI voltage are of the opposite polarity. In addition, the breakdown characteristics of SF6 gas gap with free metallic particle are investigated. It is found that under pre-stressed DC voltage, particle will do standing motion or bouncing motion. And breakdown voltage becomes lowest when particle is doing standing motion. The results of the experiments show that residual DC voltage in GIS could deteriorate its insulation ability and the combined voltage of DC and impulse is found to be a critical condition for GIS insulation. Moreover, the combined voltage is shown to be more sensitive to detect some insulation defects in GIS than applying impulse voltage alone, especially for free metallic particles, which are commonly found in GIS but up to now no effective detection method is proposed. Therefore combined voltage of DC and impulse could be considered to serve as a supplement of field test for GIS.