油液金属颗粒对500kV变压器出线装置电场的影响

Influence of Oil Metallic Particles on Electric Field of 500kV Transformer Outlet Device

近年来发生多起由出线装置绝缘击穿引起的变压器事故,初步分析表明油液金属颗粒度超标是上述事故的主要原因之一。通过建立考虑油液金属颗粒的500 kV交流变压器出线装置三维电场有限元仿真模型,研究金属颗粒尺寸和位置对出线装置电场的影响;同时,在考虑金属颗粒的情况下,研究均压球圆弧结构和油隙宽度对变压器绝缘的影响,并初步提出优化措施。结果表明:油液金属颗粒的存在可增大出线装置油隙间的最大场强,该最大场强随颗粒半径的增加而增大,甚至大于油隙许用值引起局部微放电;金属颗粒在交流电场下的振荡及放电产生的气泡可加剧电场畸变,并加速绝缘劣化进程;增大均压球圆弧半径和油隙宽度可在一定程度上降低金属颗粒作用下油隙间的最大场强,并提高油隙的绝缘裕度,可为事故分析及处理提供参考。

In recent years,there have been many transformer accidents caused by insulation breakdown of the outlet device.The preliminary analysis shows one of the main reasons for those accidents are excessive oil metallic particles.To solve this problem,this paper builds a 3D finite element simulation model for electric field of the outlet device of 500 kV AC transformer which considers oil metallic particles,and studies influence of sizes and locations of metallic particles on electric field of the outlet device.Meanwhile,in the case of considering metallic particles,it studies influence of circular arc structure of the pressure equalizing ball and oil gap width on transformer insulation and proposes optimization measures initially.The results indicate oil metallic particles may increase the maximum field intensity between oil gaps of the outlet device and the maximum field intensity may increase with increase of particle radius,or even the maximum field intensity is so greater than the allowable value that may cause partial micro-discharge.Meanwhile,vibration of metallic particles in AC electric field and bubbles produced by discharging will intensify distortion of electric field and accelerate degradation process of insulation.In addition,it is able to reduce the maximum field intensity between oil gaps under the effect of metallic particles and improve insulation margin of the oil gap by increasing circular arc radius of the pressure equalizing ball and the oil gap width,which may provide references for accident analysis.