交直流复合电场中直流电压分量对油纸绝缘沿面放电过程的影响

Effect of DC Component on Characteristics of Surface Discharge Process in Oil-paper Insulation Under Combined AC-DC Voltage

换流变压器阀侧绕组与出线装置同时承受交流、直流电压作用,使得其内部油纸复合绝缘材料的沿面放电特性与以往交流电力变压器存在较大差别,而相关研究又明显不足。为此使用典型的球-板电极结构,探索了交直流复合电场下直流电压分量对油纸绝缘沿面放电起始电压、闪络电压以及发展过程的影响,并统计分析了交直流复合电场下油纸绝缘沿面放电过程中放电信号的特征图谱,提取了不同阶段特征图谱中的特征参数。首次依据沿面放电过程中特征参数的变化规律,将交直流复合电场下油纸绝缘沿面放电发展过程划分为4个阶段:爬电起始阶段、爬电发展阶段、爬电加速发展阶段以及临界击穿阶段。研究发现不同比例交直流复合电压作用下油纸绝缘沿面放电统计特征谱图反映的特征参数变化规律,虽然在沿面放电阶段划分上是相同的,但各个发展阶段由于直流分量的不同又存在明显的差异性,直流电压分量对油纸绝缘沿面放电过程有明显的加速作用,且对绝缘纸板表面破坏较为严重。

The valve winding and outlet device of convert transformer withstand several types of voltage, including AC, DC, combined AC-DC voltages, etc. However, compared to the AC power transformer, there are great differences be- tween them about the characteristics of surface discharge of oil-paper insulation in transformer, but the characteristics of surface discharge in oil-paper insulation in converter transformer have not received enough attentions. Therefore, we used typical sphere-plate electrodes configuration to research the effect of DC component on the characteristics which was generated in surface discharge process in oil-paper insulation under combined AC-DC voltage. The spectrum diagrams of oil-paper insulation under combined AC-DC voltage were investigated, and some typical feature parameters which were obtained from the spectrum diagram by the pulse electric method were extracted. Moreover, we summarized the process of surface discharge in oil-paper insulation under combined AC-DC voltage and divided it into four stages by the regular pattern of feature parameters in the whole surface discharge process, including surface discharge initial stage, develop- ment stage, accelerating stage and critical breakdown stage. The results show that although the stage of surface discharge is the same under different DC components in combined AC-DC voltage, and there are some obviously different characte- ristics at different stages under different DC components in combined AC-DC voltage. The DC component in combined AC-DC voltage has an accelerated effect on the velocity of surface discharge process and it will seriously destroy the surface of insulate paper.