电场分量对交直流复合电场下油纸绝缘沿面放电特性的影响

Effects of Electrical Field Component on Characteristics of Creepage Discharge in Oil-impregnated Pressboard Under Combined AC/DC Voltage

油纸绝缘沿面放电现象与绝缘纸板表面的电场分布关系密切,因而使用无背面电极和有背面电极两种结构,研究了电场分量对交直流复合电压下油纸绝缘沿面放电特性的影响机制。研究结果表明：随着直流电压分量的不断增加,油纸绝缘的沿面闪络电压逐渐上升,且交流电压下的闪络电压最低;无背面电极结构下沿面闪络电压无极性效应,有背面电极结构中存在极性效应,且负极性直流电压分量作用下,由于纤维素中羟基的强电负性影响,致使沿面闪络电压较低;无背面电极结构时的闪络电压约为有背面电极结构时闪络电压的1.5倍,分析认为由于载流子受到强垂直电场分量作用,加剧了对绝缘纸板表面的碰撞,油纸绝缘空间电荷平衡状态易在较低交流电压分量作用下受到扰动而被破坏,进而诱发沿面闪络发生,致使沿面闪络电压逐渐下降,该下降趋势具有饱和现象;沿面闪络在交流电压分量接近波峰或者波谷位置处发生。

Creepage discharge phenomenon has a close relationship with the electrical field distribution on the surface of oil-impregnated pressboard（OIP）. Thus, we investigate the effects of electrical field component on characteristics of creepage discharge in OIP under combined AC/DC voltage by two electrode configurations. The experimental results show that, for both electrode configurations, there is the lowest under AC voltage, and the flashover voltage increases with DC component of combined AC-DC voltage. Besides, there is no polarity effect in the absence of back electrode configuration, but the polarity effect exits in the presence of back electrode configuration. Furthermore, the flashover voltage under the negative DC component is lower than that under the positive DC component because of higher electronegativity of hydroxyl in the cellulose of OIP. The flashover voltage in the absence of back electrode configuration is approximately 1.5 times that in the presence of back electrode configuration. However, the carriers will enhance collisions with the surface of OIP under higher vertical electrical field component. When the vertical electrical field component is higher,the creepage discharge phenomenon easily happens under a lower AC voltage component stress in the space charge balance condition in OIP. The flashover voltage decreases with a higher vertical electrical field component. When voltage is near the peaks and valleys of AC voltage component, the creepage discharge phenomenon happens.