±500 kV换流站直流分压器用复合套管外绝缘闪络事故分析及处理措施

对±500kV江陵和龙泉换流站直流分压器的外绝缘闪络事故进行了分析。指出该分压器发生闪络事故的原因:一是复合套管的憎水性完全丧失;二是复合套管的伞裙形状参数特性较差;三是复合套管的均压环结构不合理。发生闪络事故的主要原因是复合套管的憎水性完全丧失,其次是均压环结构不合理。在此基础上,针对分压器的结构和事故的性质,提出了从根本上解决问题的思路是应按所要求的电气、机械和憎水性能来选用复合套管外绝缘材料;按上下均压环中心距离和均压环直径能保证复合套管的爬电距离和干弧距离的有效性与设计值接近这一主要原则来重新设计均压环;建议复合套管的伞伸出大于或等于70mm,伞间距至少70mm来重新设计伞形。同时也建议可以采取在复合套管的外绝缘表面上涂覆加强RTV-Ⅱ型防污闪涂料来提高外绝缘强度。

Analysis and Treatment Measures on Composite Bushing External Insulation Flashover For The D.C.Divider of ±500 kV Converter Station

The ± 500 kV DC divider external insulation flashover in Gangneung and Longquan Converter Station is analyzed.The reasons of the flashover occurrence on voltage divider are indicated:First,hydrophobic of the composite bushing completely lost;Second,poor characteristic of the composite bushing sheds shape parameters;Third,irrational structure of composite bushing grading ring.Flashover occurs mainly due to hydrophobic of the composite bushing completely lost,followed by grading ring structure is irrational.On this basis,for the nature of the accident and structure of the voltage divider,it is proposed that propose the thought to radically solve the problem is to chose composite bushing insulation material according to the required electrical,mechanical and hydrophobic properties;grading ring is redesigned by the main principle that center distance and diameter of both grading ring composite casing ensures the effectiveness of creepage distance and dry-arc distance are approach the design value;it is suggested to redesign composite bushing sheds according to the sheds reach of greater than or equal 70 mm and the sheds spacing of at least 70 mm.It is also suggested to paint the enhanced RTV-Ⅱanti-pollution flashover coating on the external insulation surface to improve the insulation strength