冲击电压下SF_6棒-板间隙放电极性效应的反转现象  

Reversal Phenomenon of Discharge Polarity Effect in SF_6 Rod-plate Gap Under Impulse Voltages

作　　者：文韬[1] 张乔根[1] 郭璨[1] 张璐 马仪 谭向宇 

机构地区：[1]西安交通大学电力设备电气绝缘国家重点实验室,西安710049 [2]陕西省电力公司电力科学研究院,西安710054 [3]云南电网有限责任公司电力科学研究院,昆明650217

出　　处：《高电压技术》2015年第1期275-281,共7页High Voltage Engineering

基　　金：国家自然科学基金(51177132)~~

摘　　要：电压等级较高的系统中,由特快速暂态过电压(VFTO)引起的气体绝缘组合电器设备(GIS)绝缘事故日益严重。为给GIS绝缘结构的优化设计提供参考,研制了陡前沿冲击实验装置,并利用其研究了SF6棒–板间隙在VFTO和雷电冲击(LI)作用下的绝缘特性。结果表明稍不均匀和极不均匀电场下,SF6间隙放电均存在极性效应。稍不均匀电场下,正极性VFTO与雷电冲击50%放电电压均高于负极性。极不均匀电场中,随着气压增加雷电冲击下SF6放电出现了极性反转现象:气压较低时,负极性雷电冲击放电电压高于正极性;当气压高于某临界气压时,正极性雷电冲击放电电压高于负极性。出现极性反转的临界气压值与间隙电场不均匀系数相关,随电场不均匀度增加而减小。极不均匀场中,VFTO作用下,负极性50%放电电压较正极性高,但在较低气压时,会出现负极性VFTO放电电压低于正极性的现象。分析表明,极性效应反转是由不同极性电压下SF6间隙中空间电荷迁移和扩散的差异而形成的。Insulation failures of gas insulated switchgear（GIS） due to very fast transient overvoltages （VFTOs） is increa- singly frequent. To optimize the design of GIS insulation structure, we developed a steep fronted impulse generator, and used it to study the discharges of SF6 rod-plate gap under VFTO and lightning impulses （LI）. The results show that the discharges of SF6 gap in both quasi-uniform field and highly inhomogeneous electric field present obvious polarity features. In quasi-uniform field, the 50% breakdown voltages （U50%） of positive VFTO and positive LI are higher than those of negative overvoltages, respectively. However, in highly inhomogeneous electric field, the discharge in SF6 induced by LI shows reversion of the polarity effect with the increase of SF6 pressure： when the pressure is lower, the breakdown voltage under negative LI is higher than that under positive LI, but when the pressure exceeds a certain value, the breakdown voltage under positive LI turns out to be higher than that under negative LI. This critical pressure of polarity reversion is related to electric field inhomogeneity： it decreases with the increase of electric field inhomogeneity. Meanwhile, in highly inhomogeneous electric field, U50% of negative VFTO is higher than that of positive unless the SF6 is below a critical value. Further analysis indicates that the polarity effects are mainly due to difference in the migration and diffusion of space charges between gaps influenced by overvoltages of different polarities.

关 键 词：气体绝缘组合电器设备 特快速暂态过电压 冲击电压 SF6棒–板间隙 50%放电电压 极性效应 放电时延 空间电荷 

分 类 号：TM595[电气工程—电器]