直流下油中局部放电脉冲波形测量与特性分析

Measurement and Analysis for Pulse Current Shapes of Partial Discharge in Oil under DC Voltage

在简述直流下局部放电模型及其检测方法之后,设计了直流下局部放电试验以及具有超宽频率响应的脉冲波形测量系统.为了验证测试电路具有足够的频率响应范围,利用方波源产生的陡下降沿对测量电阻进行了校验,同时对直流下空气中电晕放电波形进行了测量,结果均表明该系统满足试验要求.在上述工作基础之上,构造了6种油纸绝缘模型以模拟换流变压器的典型缺陷,并利用该测量系统获取了缺陷模型在直流下的大量放电脉冲波形.试验结果分析表明,直流下变压器油中放电稳定,放电脉冲不存在振荡分量和过冲,放电规律与阐述的直流下局部放电模型一致,不同放电波形的特征参数均有差别.这些特性为直流下局部放电类型识别提供了试验依据.

A test system with wide frequency response was designed to measure pulse current shape of partial discharge （PD） based on the PD model and ultra-wideband detection method under direct current voltage. The measuring impedance was tested by square wave with very steep trailing edge and the corona in air under DC voltage was detected, which confirms the validity of the whole system. According to the defect analysis in oil-paper insulation of converter transformer, six corresponding PD defect models were constructed to gain the PD pulse current shapes. The results show that the PD pulse current shapes of the defects in oil under DC voltage get nonoscillatory without overshoot and the characteristic parameters of the pulse current shapes differ from each other for different defect models, which coincides with the discharge model under DC voltage mentioned above.