油纸绝缘系统中含高水分绝缘纸板的沿面爬电特性

Creepage Discharge Performance of High Moisture Pressboard in Oil-paper Insulation System

水分是导致沿面爬电的重要原因之一,为研究高水分质量分数绝缘纸板的沿面爬电特性,分析了实际变压器中绝缘纸板可能达到的高水分质量分数值,建立了绝缘纸板沿面爬电特性试验装置,制备了相应高水分质量分数的绝缘纸板,对其沿面爬电过程进行了观测。研究结果表明:油中水分质量分数在30×10-6时,变压器中绝缘纸板的局部水分质量分数有可能达到7%以上,其沿面爬电平均起始场强仅为约0.3 kV/cm,远低于实际变压器中的许用场强;沿面爬电首先在高低压电极处的卡槽连接处起始,放电量可达20000 pC,呈间歇性发展,会在绝缘纸板表面造成碳痕与"白斑"等损伤;沿面爬电的产气率较大,产生气体中H2、C2H2和CO的体积分数较高。

High moisture in pressboard may be a predominant factor causing creepage discharge failure in power transformer. To research the creepage discharge performance of high moisture pressboard, possible high moisture in pressboard of power transformer was analyzed according to Oommen paper-oil moisture equilibrium curves, and a creepage discharge simulation and test setup and measurement system were established, which were consisted of creepage discharge model, test tank, Zhongfen 2000 A gas-phase chromatographic instrument, and DST-4 partial discharge detector. Moreover, a creepage discharge model was constructed by 25 cm-long pressboard between plate electrode and ball electrode. When the moisture of pressboard reached 7% in creepage discharge process, the appar- ent discharge magnitude and dissolved gases in oil were measured. The results show that moisture of part pressboard may reach to 7% when oil） moisture is 30× 10^-6, and the inception electric field strength of ereepage diseharge is on- ly about 0.3 kV/cm which is much lower than available electric field strength of transformer; creepage discharge ap- pears at small oil gap in high voltage and ground electrode firstiy and its apparent discharge magnitude is about 20000 pC; creepage discharge is intermittent and even stops at some time; bright are and lots of bubbles can be ob- served; dissolved gases contents generated by creepage discharge are very high, especially H2, CO and Cz Hz.