高压电缆接头界面气隙缺陷模拟及状态特征量分析

Simulation of Interface Air Gap Defect in High Voltage Cable Joint and Its State Characteristic Quantities Analysis

由于安装缺陷或运行中不均匀发热膨胀等因素,高压电缆中间接头会形成界面气隙缺陷,运行过程中易导致故障发生。本文分析了界面气隙缺陷的形成原因,仿真计算了不同缺陷程度下的电场分布特征,并通过模拟试验研究综合工况下各类带电检测手段、在线监测手段的检测有效性,以及不同电压、不同负荷电流工况下状态特征量的变化规律。结果表明:高压电缆中间接头界面气隙缺陷位于应力锥与本体交界面时,电场强度最大并会发生局部放电;局部放电是反映界面气隙缺陷状态的有效特征量,高频局放带电检测和在线监测、超声波局放带电检测均可检出较明显的放电信号,而测温和接地电流在线监测均未发现异常;试验电压和试验电流恒定工况下,随着时间的延长,高频局放和超声局放信号幅值呈增大趋势;试验电压恒定而试验电流升高工况下,局放信号幅值略微增大;不同试验电压工况下,随着试验电压的升高,局放信号幅值呈明显增大趋势。

Due to the installation defects or non-uniform thermal expansion during operation of high voltage cable intermediate joints, there will be interface air gap defect formed in the cable joint, which can easily lead to faults during operation. In this paper, the formation reasons of interface air gap defect were analyzed, and the electric field distribution characteristics under different defects were simulated and calculated. The detection effectiveness of various live detection methods and on-line monitoring methods under comprehensive operating conditions were studied by simulation tests, and the change law of characteristic quantities under different voltages and different load currents was analyzed. The results show that when the interface air gap defect is located at the interface between stress cone and cable body, the electric field strength is the largest and partial discharge would occur. The partial discharge is an effective characteristic quantity reflecting the status of interface air gap defect, and the high frequency partial discharge live detection and on-line monitoring, as well as ultrasonic partial discharge live detection, can detect obvious discharge signals, while the temperature and ground current online monitoring have no abnormal finding. Under constant test voltage and current conditions, the amplitude of high frequency partial discharge signals and ultrasonic partial discharge signals increase with the increase of time. When the test voltage is constant and the test current increases, the amplitude of partial discharge signals increases slightly. Under different test voltages, the amplitude of partial discharge signals increases obviously with the increase of test voltage.