正极性雷电冲击电压下天然酯绝缘油油纸沿面流注动态变化规律研究

油纸绝缘复合电介质沿面放电是电力设备内绝缘的研究基础,其在雷电冲击电压下的绝缘特性是变压器绝缘设计的重要参数之一。为了获得油纸沿面流注传播与消散过程中电学、空间电荷分布演化规律及其关联关系,以交界面平行于施加电场方向的油纸系统为研究对象,通过构建适用于绝缘油油纸沿面流注动态变化特性的试验观测系统,可同步获得正极性雷电冲击电压下流注传播和消散过程中的电压、放电电流和放电通道流注阴影图像。利用该平台还测量了油纸沿面正极性雷电冲击击穿电压。试验结果表明,在正极性雷电冲击电压下天然酯绝缘油油纸绝缘相对介电常数差异并不会促进油纸沿面流注的传播过程,而粘度对于油纸沿面流注侧向分支影响显著。粘度越低,空间电荷在迁移过程中所受到的阻力越小,流注头部空间电荷在受到表面电荷的斥力后越容易往油中扩散,空间电荷在绝缘油中所形成的空间电场使得油纸沿面流注的主分支能够在绝缘油中传播,增加了油纸沿面流注传播距离,从而使低粘度天然酯绝缘油油纸沿面正极性雷电冲击击穿电压略高于其纯油击穿电压。

Study on the Dynamic Characteristics of Streamer Along the Interface Surface of Natural Ester Insulating Oil-pressboard System Under Positive Lightning Impulse Voltage

The surface discharge on oil-pressboard insulation systems is the research basis of the internal insulation of power transformer, whose insulation characteristic under lightning impulse(LI) voltage is one of the important parameters of transformer insulation design. In order to obtain the evolution law of electrical parameters and space charge distribution and their relationship, the oil-pressboard system with the interface oriented parallel to the primary electric field direction was taken as the research object, and the observation system for dynamic characteristics of streamer was constructed. The system could simultaneously obtain the voltage, discharge current, and streamer shadow images during the propagation and dissipation process of the streamer under positive LI voltage. The positive LI surface breakdown characteristics of ester insulating oil-pressboard system were also obtained. The results show that the difference in the relative permittivity of oil-pressboard insulation does not propagate the development of the streamer along the interface surface of the ester insulating oil-pressboard system under positive LI voltage. The viscosity has a significant influence on the lateral branch of streamer along the interface surface of the ester insulating oil-pressboard system. The drag force of space charge during the migration process was smaller due to the ester insulating oil with lower viscosity, and then the space charge diffused into the ester insulating oil more easily by the repulsion force of surface charge. The electric field formed by space charge in oil makes the main branch of the streamer propagate in the oil and increases the distance of the streamer so that the positive LI breakdown voltage of the oil-pressboard system was higher than that of pure oil.