基于Kerr电光效应测量的液体空间电荷产生及其分布特性

Generation and Distribution Characteristics of Space Charge in Liquid Dielectric Based on Kerr Electro-optic Effect

空间电荷是影响绝缘介质耐电强度,导致电场分布畸变和电介质击穿的重要参数之一。为了更深入地开展液体中空间电荷产生及其分布特性的试验及相关机理研究,采用基于Kerr效应的空间电荷高速CCD(charge-coupled device)测量系统,实现了碳酸丙烯酯中黄铜、不锈钢、铝3种电极材料在冲击电压下光强分布特性的测量;结合改进的图像处理技术,对极间电场随时间变化的动态发展过程进行反算;同时依据传统电击穿理论和双电层理论对空间电荷产生及发展的微观机理进行分析。研究表明:在不同材料以及不同电压极性下,空间电荷分布呈现出双极注入、正电荷注入及负电荷注入3种显著的注入特征,其中双极注入提高了液体电介质的冲击绝缘性能,正电荷注入和负电荷注入使得液体电介质绝缘性能降低,其注入特性的差异与外加电压大小、电极材料、电极表面状态等因素有关。

Space charge is one of the most important parameters that determine the electricfield and insula tionbreakdown performances of dielectrics. In order to further understand the generation and distribution of space charge in liquid dielectric, we adopted a highspeed CCD measuring system, which is mainly based on Kerr electrooptic effect, to measure the light intensity distribution in HV pulsed propylene carbonate （C4H603）. Parallelplane electrodes of brass, stainless steel, and aluminum were used in the measurements. Then, with the refined image processing technique, we cal culated the temporal variation of electricfield dynamic process. Finally, we analyzed the microcosmic mechanisms of space charge＇s generation and transportation by traditional electric breakdown theories and the double charge layer theory. It is concluded that the space charge distributes in three different patterns, namely the bipolar homocharge injection, posi tive charge injection, and negative charge injection, according to different electrode materials and source polarity. The bipolar homocharge injection can improve the impulse insulation performance of liquid dielectric, whereas the other two can weaken the insulation performance of the dielectric. Additionally, voltage amplitude, electrode materials, and surface conditions of electrode have serious effects on the injection pattern.