针板电极交直流复合电场中局部放电的发展过程

The Partial Discharge Evolution of Needle-plate Electrode Under Hybrid AC and DC Electric Field

换流变压器阀侧绕组工作电压环境复杂、故障率高,所以绝缘问题突出。本文在恒压条件下,利用常规脉冲电流法实时记录交直流电压共同作用下针板模型油纸复合绝缘系统中局部放电发展的过程。从发展过程中各统计时间段放电次数相位柱状谱图特点、放电次数和放电量及油中气相色谱变化趋势所表现出的现象中,提取能够有效表征交直流复合场放电发展过程的特征量,用以初步判断绝缘介质劣化的严重程度。实验结论:伴随放电严重程度的增加,放电次数相位柱状谱图中的放电相位带拓宽;结合发展过程中放电次数、放电量演化的增减趋势特点,初步提出放电发展过程中放电阶段的划分依据;油中分解气体含量的变化"平稳激增"的特点可作为绝缘介质绝缘强度劣化的外在表征。

The operation voltage of winding of converter transformer at valve side is complex and its failure rate is high,so issues on the insulation deterioration is serious.In this paper,the partial discharge （PD） evolution process of oilpaper composite system with needle-plate model under hybrid AC and DC voltage is recorded real-time by normal pulse current method.The characteristic quantities that represent the discharge evolution of hybrid AC and DC electric field can be effectively extracted from information,such as the phase columnar spectra of discharge stages,the discharge capacity,the number of PD and the dissolved gas analyze （DGA） and so on,to initially judge the degree of insulation deterioration.The experiments show that：1） Phase band of discharge in columnar spectra becomes wider with the growing degree of discharge; 2） a criterion to partition the discharge phase during discharging process is presented by considering the tendency of both the discharge times and the discharge capacity; 3） The content of the dissolved gas in oil keeps steady increasing rate in the pre-stages while has a sharp rise in the final stage,which can be used as external representation of the insulation deterioration degree.