油老化状态对油纸绝缘直流电场下空间电荷特性的影响

Effect of Oil Aging States on the Space Charge Behavior in Oil-paper Insulation Under DC Electric Field

为了深入研究油老化对油纸绝缘直流电场下空间电荷特性的影响,通过加速热老化得到三组不同老化程度的绝缘油试样,并对其进行理化及电气特性分析;然后利用所得油样分别对经过真空干燥的新绝缘纸进行真空浸渍,得到3组油老化状态不同的油纸绝缘试品;进而采用电声脉冲法(pulsed electro-acoustic,PEA)在室温下分别测量了3组试品在施加直流电压和撤除电压情况下的空间电荷分布,讨论了油老化状态对油纸绝缘试品中空间电荷注入、积聚及消散等特性的影响。实验结果表明:施加直流电压下,3组油浸纸试品与电极界面处均发生了同极性电荷注入现象,油老化程度越严重,电极与介质界面处感应的电荷密度峰值越大,积聚在试品中的空间电荷总量也逐渐增大,负电荷积聚区域逐渐向阳极方向推进。撤除电压后,随着绝缘油老化程度的加重,试品中的空间电荷消散速率增大,且正电荷的消散速率大于负电荷的消散速率。

In order to deeply understand the effect of oil aging state on space charge behavior in oil-paper insulation under DC electric field,transformer oil samples with different aging states were prepared by accelerated thermally aging,and their physical and chemical properties were analyzed.Then new Kraft papers were dried in vacuum and immersed in oil above with different thermally aging states,and three kinds of oil-paper samples were achieved.The pulsed electro-acoustic（PEA） method was used for space charge measurement under both DC voltage-on and voltage-off conditions at room temperature.The impact of oil aging state on the characteristics of space charge injection,accumulation and decay was discussed.Experimental results show that homocharges are injected into samples at the interface of electrode and dielectric when DC voltage is on.When the aging state is worse,more charges are induced at both cathode and anode,as well as more space charges accumulate in the bulk.Besides the more the oil aging state is,the larger the area of negative charges is.For voltage-off condition,aging oil is beneficial for space charge decay.Moreover,trapped positive space charges decay faster than trapped negative charges.