摘要
为解决换流变压器阀侧主绝缘所面临的击穿问题,探讨了极性反转电压下油纸复合绝缘的击穿机理。利用平板电极模型,在极性反转、台阶升压直流和缓慢升压直流3种电压类型下,对油隙、浸油纸板和油纸复合绝缘3种样品进行了击穿电压试验研究。测量了极性反转电压下流过3种样品的电流,在此基础上确定了油纸复合绝缘的等值电路,建立了电压方程并进行了电压分布数值解析。研究结果表明,油隙击穿电压随电压施加时间增加明显下降,浸油纸板击穿电压基本不随电压施加时间变化。油隙样品不在极性反转过程击穿。浸油纸板和油纸复合绝缘样品全部在极性反转过程击穿,极性反转造成击穿电压下降。由绝缘电流核算的变压器油的绝缘电阻非线性,它随施加电场强度升高而下降,暂态时还随电场施加时间增加而下降。由剩余电流核算的浸油纸板的绝缘电阻符合欧姆定律。在极性反转过程,受变压器油绝缘电阻非线性影响,油纸复合绝缘中油隙分布电压会快速反转后持续较高的水平,这一计算值与变压器油击穿电压试验结果相吻合。
In order to solve the breakdown problem that the main insulation on valve side of the converter transformer face, the breakdown mechanism of the oil-pressboard insulation under the polarity reversal voltage was explored. Using a pair of plate electrode models, breakdown voltage experiments on three kinds of samples such as the oil-gap, the oil immersed pressboard and the oil-pressboard insulation were carried out under the polarity reversal, the step DC and the slowly increasing DC voltage. Currents of three kinds of samples under the polarity reversal voltage were measured. Based on these, the equivalent circuit of the oil-pressboard insulation was determined. The voltage equation was established and the voltage distribution was numerically analyzed. Research results indicate that, the breakdown voltage of the oil-gap apparently decreases with the increase of the voltage application time, but the breakdown voltage of the oil immersed pressboard has little change. The oil-gap sample is not broken down during the polarity reversal. All of the oil immersed pressboard samples and the oil-pressboard insulation samples are broken down during the polarity reversal, so the polarity reversal causes decrease of the breakdown voltage. The insulation resistance of the transformer oil which is calculated by the insulation current is nonlinearity. It will decrease with the increase of the electric field strength and with the increase of the application time in the transient. The insulation resistance of the oil immersed pressboard which is calculated by the residual current is in line with the ohm＇s law. During the polarity reversal, the voltage on the oil-gap of the oil-pressboard insulation which is affected by the nonlinearity of the transformer oil insulation resistance can keep a high level after a rapid reversal, this calculated value coincides with the breakdown voltage result of the transformer oil-gap.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2015年第21期5656-5666,共11页
Proceedings of the CSEE
基金
国家重点基础研究发展计划资助(973项目)(2011CB 211707)~~
关键词
换流变压器
极性反转
油纸复合绝缘
击穿机理
converter transformer
polarity reversal
oil-pressboard insulation
breakdown mechanism
