交直流复合电压下老化油纸绝缘针板模型局部放电特性

Partial Discharge Characteristics of Needle-plate Electrodes in Aging Oil-paper Insulation Under Combined AC-DC Voltage

为研究换流变压器阀侧实际运行老化的油纸绝缘局部放电特性,提高交直流复合电压下油纸绝缘局部放电研究的工程实际意义,取运行5 a的换流变油纸样本,建立典型针板电极油纸绝缘缺陷模型,对交直流复合电压下老化油纸绝缘局部放电从起始阶段到击穿的整个过程进行了实验模拟并记录放电时域信号。随着局部放电发展,放电幅值逐渐提高,出现放电的相位分布扩大,相应相位出现的放电次数增加,当临近击穿时,负周期放电量超正周期数倍。基于时域放电信号建立了多个放电周期的H_(umax)(φ)、H_(umean)(φ)、H_n(φ)和H_n(u)等PRPD谱图。分析谱图特性,并计算各个谱图的偏度(Sk)等统计参量因子,基于自适应阈值模糊聚类分析方法,将统计参量因子分为10类,分类之后可看出一定的时间延续性。结合分类结果和局部放电发展的不同时刻的信息,将放电模型的发展过程划分为初始放电阶段、放电发展阶段、放电稳定阶段和预击穿阶段。划分结果可为交直流复合电压下油纸绝缘局部放电在线监测和模式识别提供参考。

In order to study the partial discharge（PD） characteristics of aging oil-paper insulation in the actual operation condition of converter transformer valve-side, and to improve the engineering significance of the research on PD of oil-paper insulation under combined AC-DC voltage, by using the oil-paper samples from a 5-year-old converter transformer, we established a needle-plate electrode model to simulate the whole process of PD from the beginning to breakdown in ageing oil under the combined AC-DC voltage. The recorded time domain signals show that, with the de- velopment of PD, the discharge magnitude gradually increases,the phase distribution expands, and the number of pulses of each phase increases.When approaching breakdown, PD magnitude in negative half cycle is several times higher than that in positive half cycle.Based on the time domain signals PRPD spectra of Humax（φ）, Humean（φ）, Hn（φ） and Hn（u） with multiple discharge cycles is set up. The spectra characteristics are analyzed, and the statistical parameter factors of the spectra like skewness （Sk） are calculated. The statistical parameter factors are classified into 10 time continuous types with the adaptive threshold fuzzy clustering analysis method.Combined with the classification results and the information of PD development at different times,the PD process is divided into 4 stages： initial stage, developing stage, stable stage, and pre-breakdown stage.The results can be used as a reference for on-line monitoring and pattern recognition of oil-paper insulation under combined AC-DC voltage.