XLPE直流电缆典型缺陷局部放电特性研究

局部放电是表征电力设备绝缘状态的最有效的手段之一,然而关于直流电压下XLPE电缆典型绝缘缺陷局部放电特征的研究较少。文中首先深入分析了直流下复合绝缘材料局部放电机理,总结了XLPE电缆常见缺陷类型及其原因。使用单芯XLPE电缆及其预制式接头制作了金属毛刺电晕缺陷、应力锥处半导电层沿面放电缺陷以及绝缘交界面气隙放电缺陷,在直流电压下进行阶梯式加压试验。基于高频电流法采集局部放电数据,获得了各缺陷不同放电严重阶段的多种典型特征,包括放电量-时间间隔-放电重复率三维图谱,前序放电量、前序放电时间间隔与当前放电量相关性散点图。提取了典型统计图谱的28个指纹特征,并使用RBF神经网络进行模式识别获得了较好识别正确率,从而验证了特征有效性。

Research on Partial Discharge Characteristics of Typical Defects in XLPE Cables Under DC Voltage

Partial discharge(PD)is one of the most effective means to characterize the insulation states of power equipment.However,there are few studies on partial discharge characteristics of typical insulation defects in XLPE cables under DC voltage.Firstly,the mechanism of partial discharge of composite insulation under DC voltage is deeply studied in this paper.And common types of defects and their causes in the XLPE cable are summarized.Three kinds of defect models are designed using XLPE cable and its prefabricated joints,including corona discharge,surface discharge at the stress cone,and air gap discharge at the insulation interface.The experiment is tested under step-wise DC voltage.Several typical features of different severity stages of the discharges are obtained based on the PD data measured by High frequency current method(HFCT),including the three-dimensional map of discharge magnitude-time interval-discharge repetition rate,the scatter plots of previous discharge magnitude or previous time interval with the current discharge magnitude.28 fingerprint characteristics are obtained and a good recognition accuracy can be obtained based on the RBF neural network.