高频电压下油纸绝缘系统的局部放电及产气特性研究

Research on Partial Discharge and Gas Production Characteristics of Oil-paper Insulation System Under High Frequency Voltage

高频变压器在提升电能传输效率的同时,也会加速油纸绝缘系统缺陷的劣化进程。为研究油纸绝缘系统在高频电压下的劣化特性,采用柱板模型模拟油纸绝缘的沿面放电缺陷,搭建高频局部放电试验平台,在10、20、30 k Hz电压下采用恒压法进行多组局部放电试验。利用摄像机和罗氏线圈分别记录试验现象和放电信号,分析高频电压下局部放电图谱和产气特性,并与工频局部放电试验的结果进行对比。结果表明:随着频率的提高,油纸绝缘系统的局部放电起始电压显著降低,单位时间内关键气体的产气量明显提高;但在高频电压下,绝缘油的劣化比绝缘纸板的劣化更为严重,因此提高了关键气体中H2的比例。由于空间电荷效应,放电相位集中于电压极性反转相位附近,且高频电压下的放电相位比工频电压下的放电相位宽;同时,在高频电压下,电压的上升速率、单周波内的有效放电时延受到频率的影响,使单周波内的平均放电幅值、平均放电次数在20 k Hz附近出现极大值。

High frequency transformer is favorable to boost the efficiency of transporting electricity,but it leads tocritical challenge to insulation system inside. To investigate the partial discharge characteristics of defects in oil-pa-per insulation systems under high-frequency voltage,a platform for partial discharge test is established,in which acolumn-plate model is adopted to simulate the surface discharge defect. Tests under high-frequencies of 10 k Hz,20 k Hz and 30 k Hz and power frequency of 50 Hz are set up,where constant voltages are applied. The experimentalimages are recorded by video camera,partial discharge signals by Rogowski coil. Characteristics of partial dischargeand dissolved gas production under different frequencies are compared and analyzed. Conclusions can be drawn thatthe partial discharge inception voltages of partial discharge signals under high-frequency voltage are much lower thanthat of power-frequency voltage,whereas the content of key gases especially H2 are boosted,indicating that the oil-pressboard insulation especially insulating oil are deteriorated more severely. Also,the partial discharge signals cen-ter on the time when the polarity changes resulting from the effect of space charge. Meanwhile,the discharge phaserange under high frequencies are wider than that under power frequency. Lastly,the du/dt and the effective time de-lay are affected by the frequency,thus,the average amplitude and times of partial discharge（PD）appear a peak val-ue around 20 k Hz in a single period.