XLPE电缆半导电层对局部放电传播特性的影响分析

Influence of XLPE cable semiconducting layer on the propagation property of partial discharge

目前电力电缆局部放电在线监测研究中,很少考虑半导电层导致的局部放电(PD)脉冲传播特性研究不准确的问题。研制一种改进型PD发生电路和电缆本体模型,首先,在考虑电缆内半导电层的条件下,搭建改进型五电容PD发生电路,研究内半导电层电阻率、介电常数及厚度对PD脉冲上升沿的影响;然后,把内半导电层分为等效导体层和等效绝缘层,并在等效层两边各引入虚拟层,建立电缆本体模型;最后,对单相500 k V XLPE电缆系统模型进行仿真,研究内半导电层的等效导体厚度和等效绝缘厚度对PD传播速度和衰减系数的影响。仿真结果验证了内半导电层对PD信号具有影响,所提出的改进型PD发生电路与电缆本体模型结合之后,用于研究PD传播特性更合理,且能得到更准确的PD脉冲传播特性。

In the current online monitoring method of power cable partial discharge（PD）, the PD pulse propagation property is inaccurate caused by the semiconducting layer. An improved PD pulse generating circuit and a cable body model are proposed in this paper. Firstly, considering the inner semiconducting layer, the improved five-capacitance PD generating circuit was established, and the influences of the semiconducting layer’s resistivity, relative permittivity and thickness on PD pulse rising edge were studied. Secondly, the inner semiconducting layer was divided into an equivalent conductor layer and an equivalent insulation layer, and the virtual layer is added to the both sides of the equivalent layer. The single-phase 500 kV XLPE cable model was set up. Finally, based on the simulation results, the influences casued by the thickness of equivalent conductor and equivalent insulation within the inner semiconducting layer on PD propagation velocity and attenuation coefficient was studied. The simulation results show that the proposed model is reasonable and can be used to obtain more accurate pulse propagation property.