交联聚乙烯直流电树枝降压阶段的局部放电特性  

Partial Discharge Characteristics of DC Electrical Tree in XLPE During Voltage Drop

作　　者：林国海 张洪亮 郑喆 王亚林[1] 周明瑜 尹毅[1] LIN Guohai;ZHANG Hongliang;ZHENG Zhe;WANG Yalin;ZHOU Mingyu;YIN Yi(Department of Electrical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Global Energy Interconnection Research Institute Europe GmbH,Berlin DE-10623,Germany)

机构地区：[1]上海交通大学电气工程系,上海200240 [2]全球能源互联网欧洲研究院,柏林DE-10623

出　　处：《高电压技术》2024年第1期348-358,共11页High Voltage Engineering

基　　金：国家电网公司总部科技项目(5500-202158298A-0-0-00)。

摘　　要：电树枝是交联聚乙烯(XLPE)高压直流电缆的典型缺陷,有效检测电树枝对电缆绝缘状态评估至关重要。为此对含有电树枝的XLPE针-板绝缘试样进行直流局部放电实验,分析不同阶段下的局部放电特性以及电压参数对放电特性的影响。实验发现:含电树枝的试样在降压过程中会出现局部放电现象,不含电树枝的试样则不会放电;降压过程中的放电具有良好的重复性,对电树枝尺寸无明显影响,且放电脉冲极性与恒压阶段的相反。该实验现象表明利用降压阶段的局部放电检测,可为高压直流电缆电树枝的评估提供一种有益的尝试。此外,实验表明多次局部放电可能导致通道电导率增加,放电熄灭电压增大。不同电压参数下的降压阶段实验结果表明:更高的直流电压,合适的降压速率可以增加放电次数;针电极为负极性时平均放电量更高;恒压时长对放电特性没有显著影响。采用数值仿真分析了降压前后绝缘区域的电场分布,结果表明降压前期,泊松电场的衰减速率低于外施电场的衰减速率,使得针尖附近形成场强较高的反向电场,从而导致降压过程中的局部放电。The electrical tree is a typical defect of XLPE HVDC cables.Effective detection of the tree is of vital im-portance for the evaluation of cable insulation status.In this paper,DC partial discharge(PD)experiments were carried out on the XLPE insulation samples with electrical trees.The characteristics of PD at different stages and voltage param-eters were analyzed.It is found that PD occurs in the samples with electrical tree defects during the DC voltage drop,while the samples without electrical trees have no PD.The polarity of the PD during the voltage drop is opposite to that in the constant voltage stage.The PD shows good repeatability and has a negligible effect on the tree size.The experiment shows that the PD detection in the voltage drop stage can provide a reference for the evaluation of the electrical tree of HVDC cables.In addition,the experiment shows that multiple PD may lead to the increase of tree conductivity and PD extinction voltage.The experimental results of different voltage parameters show that higher DC voltage and appropriate voltage reduction rate can increase the PD number.The average PD amplitude is higher when the needle electrode suffers negative voltage.Constant voltage duration time has a negligible effect on PD characteristics.Numerical simulation was used to analyze the electric field in the insulation during the voltage drop.The study shows that the attenuation rate of the Poisson electric field is lower than that of the applied electric field in the early stage,which results in the formation of a reverse electric field with high intensity around the needle tip,thus resulting in PD during the voltage drop.

关 键 词：交联聚乙烯 直流电树枝 局部放电 空间电荷 绝缘诊断 

分 类 号：TM855[电气工程—高电压与绝缘技术]