直流电场下油纸绝缘介质界面处的空间电荷特性

Space Charge Characteristics of the Interface in Oil-paper Insulation Under DC Voltage

换流变压器是直流输电系统的核心设备,其油纸复合绝缘结构的空间电荷特性复杂,工程实践表明其对绝缘放电的影响不可忽略,因此针对油纸复合绝缘开展空间电荷特性的研究对换流变绝缘结构设计和运行分析有指导意义。为此,应用电声脉冲(PEA)法研究了电场对双层油浸纸介质中空间电荷特性的影响以及界面处的空间电荷特性。指出在双层油浸纸的界面处将积聚负电荷,无论是极化还是去极化过程,双层油纸介质中的空间电荷的积聚和消散均较缓慢。在较高场强的作用下,阳极电荷注入过程的加强掩盖了阳极附近的电离过程。研究认为双层介质界面势垒是造成介质内部空间电荷运动缓慢的根本原因。而界面处负空间电荷的积聚则由势垒陷阱捕获和界面两侧场强差异导致电导差异两个过程共同决定。

We investigated space charge distribution in a two-layer oil-paper insulation system using the pulsed electroacoustic （PEA） technique, and analyzed the effects of electric field and interface on space charge characteristics. The test results show that both interface and electric field affect the behavior of space charge. The interface between two oil-paper layers acts as a barrier to negative charge, as a result, negative charge accumulates adjacent to the interface. The space charge accumulation and dissipation in two-layer samples is slow whether it is in the process of polarization or depolarization. Under a higher electric field, the enhancement of the process of space charge injection at the anode covers the process of ionization near the anode. We believe that the potential barrier at the interface between two-layer dielectrics is the root cause of the slow motion of the space charge inside. While the accumulation of negative charge at the interface is decided by the capturing of barrier traps and the difference of conductivity between both sides of the interface , which is caused by the diversity of electric field inner each layer.