基于改进电声脉冲测试系统的油纸绝缘混合体系空间电荷动态行为特性

Space Charge Migration Characteristics of Transformer Oil-Paper Insulation Based on the Improved Pulsed Electro-Acoustic Measurement System

目前国内外关于油纸绝缘介质空间电荷特性的研究全部基于油浸绝缘纸,且已有的电声脉冲测试系统无法实现对油隙与油浸纸组合而成的混合体系的空间电荷特性的测试。通过采用改进的电声脉冲测试系统首次对油隙与油浸纸板组合而成的混合体系的空间电荷动态行为特性进行研究,分析空间电荷积聚对油纸混合体系内部电场分布的影响。研究发现油纸绝缘界面处及油浸绝缘纸内部积聚的空间电荷和电场畸变程度与绝缘油和油浸纸板的电导率关系很大。由绝缘油劣化导致油纸绝缘系统的电导率提升更易引起油浸纸内部场强严重畸变,油浸纸内部最大场强约达到平均场强的2.5倍。而由油浸纸电导率增大引起的油纸绝缘系统的电导率提升减轻了油浸纸内部的电场畸变程度,但电荷快速迁移会导致介质热效应显著也易诱发击穿。消除绝缘结构界面引起的空间电荷积聚效应、限制空间电荷在绝缘介质内部的快速迁移或使电荷在介质内部分布更加均匀,从三方面出发将有助于抑制空间电荷的危害。

At present, most of the researches on space charge characteristics of oil-paper insulation are based on oil impregnated insulation paper. The pulse electro-acoustic system fails to test the space charge characteristics on the mixed insulation with the combination of oil gap and oil impregnated insulation paper. In this paper, the dynamic space charge behaviors of the mixed insulation with the combination of oil gap and oil impregnated insulation paper were studied, using the improved pulse electro-acoustic measurement system for the first time. The effect of space charge accumulation on internal electric field distribution of the mixed insulation system was analyzed. Results show that the conductivity of the oil or the oil impregnated insulation paper has great effects on the space charge and the electric field distortion at the interface and inner of the oil-paper insulation. The insulating oildegradation increases the oil-paper insulation system conductivity, which causes serious electric field distortion inside the oil-paper insulation. The largest electric field strength inside the oil impregnated insulation paper is about 2.5 times higher than the average electric field strength. The conductivity of the oil-paper insulation system increases as the oil impregnated paper conductivity increases, which reduces the electric field distortion inside the oil impregnated paper. But the rapid migration charge will result in significant heat effect that also easily induces breakdown. The following three aspects would be helpful to prevent the damage of space discharge, i.e., eliminating the space charge accumulation effects at the insulation structure interface, limiting the rapid migration of space charge inside the dielectrics or making the charge distributed more evenly within the dielectrics.