一例500kV变压器感应耐压试验击穿原因分析及处理

本文针对一例出厂验收过程中的耐压击穿事故,通过油色谱分析、吊芯检查找到了放电击穿点,通过对比设计图确定了中性点和低压引线间缺少绝缘垫块的施工缺陷,分别采用模拟电荷法和有限元法搭建模型,计算了引线间的场强分布。计算结果表明在幅值电压下,无垫块时极间场强达到200 kV/cm,发生油中放电击穿概率大,按标准安装后最大场强不超过40 kV/cm,绝缘裕度较大。文中最后对此提出了预防措施,有利于设备质量管控和绝缘考核分析工作的开展。

Breakdown Analysis of a Test of Inductive Withstand Voltage for 500 kV Transformer

In this paper,the breakdown point of discharge is found by oil chromatograph analysis and core suspension inspection,and the construction defects of lacking insulation pad between neutral point and low voltage lead are determined by comparing the design drawings,the charge simulation method and the finite element method are separately used to build the model and calculate the field intensity distribution between the leads.The results show that the field strength between electrodes is up to 200 kV/cm,the breakdown probability is large,but the maximum field strength is not more than 40 kV/cm after standard installation,and the insulation margin is large.At last,the preventive measures are put forward,which is beneficial to the quality control of equipment and the analysis of insulation examination.