为研究XLPE电缆的绝缘特性,用极化-去极化电流(PDC)法对新电缆和经改进水针法制备的不同老化程度的电缆进行实验.实验发现:在极化电压相同的情况下,水树老化电缆的泄漏电流值和去极化初期电流值比新电缆高出至少一个数量级;随着极化电压的升高,新电缆的泄漏电流值基本上呈线性增大,而经过水树老化实验的电缆泄漏电流值呈非线性增大,且老化时间越长,非线性程度越大.定义了快速非线性(FNL)因子,以获取不同绝缘状态电缆非线性程度的差异,从而评估电缆的老化程度.同时,根据实验电缆的实际参数建立了水树老化电缆有限元模型,仿真结果很好地验证了由XLPE水树引起的水树老化电缆绝缘非线性变化的特性.
In order to study the insulation performance of XLPE cables,new cables and XLPE cables with different ageing degrees obtained by improved water-needle method were tested by polarization-depolarization current (PDC) method.The results show that the leakage current and initial depolarization current of the water-tree aged XLPE cables are one order of magnitude higher than that of new cables under the same polarization voltage.With the increase of polarization voltage,the leakage current of new cables increases linearly,while the leakage current of the aged XLPE cables increases nonlinearly,and the degree of nonlinearity increases with the ageing time.A fast-non-linear (FNL) factor was defined to obtain the difference of nonlinearity level of cables with different insulation state,and then to assess the ageing degree of cables.Meanwhile,a finite element model was built according to the parameters of cable samples,the simulation results verified the nonlinear characteristics of the aged cable insulation caused by water tree.
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