高压XLPE电缆绝缘多参数在线监测

On-line monitoring of multiple insulation parameters of high voltage XLPE cable

建立了在交流电压作用下高压交联聚乙烯(XLPE)电缆绝缘的参数模型,并分析了电缆绝缘劣化时绝缘参数的外在表现。提出通过监测XLPE电缆的工作绝缘电阻、等值电容、介质损耗因数及各参数的变化趋势来综合评定电缆的绝缘状况,并分析了该方法的有效性及合理性。设计了高压XLPE电缆在线监测装置。在数据处理方面,采用基于LM(Levenberg-Marquardt)算法的非线性最小二乘拟合法对采样信号进行拟合,将信号进行快速傅里叶变换得到的谐波分析结果作为LM算法的迭代初值,并利用拟合结果计算出电缆绝缘的被监测参数。仿真分析表明,该算法收敛速度快、精度高,能很好地抑制电网频率波动、直流分量以及谐波含量对被监测参数的影响。

The insulation parameter model of XLPE （crosslinked polyethylene） cable exerted by AC voltage is established,and the behavior of insulation parameters of the cable with deteriorated insulation is analyzed. It is suggested to comprehensively evaluate the insulation condition of XLPE cable by its working insulation resistance,equivalent capacltance,dielectric loss factor and their change tendency,which is analyzed in availability and rationality. An on-line monitoring system of high voltage XLPE cable is designed. Nonlinear least square fitting based on LM （Levenberg-Marquardt） algorithm is applied in the fitting of sampled signals. The harmonics obtained by fast Fourier transform analysis is taken as the initial values of LM and the fitting results are used to calculate the monitored parameters. Simulation results show that,the algorithm has fast convergence and high precision,and better restrains the influences of frequency fluctuation ldirect current component and harmonic contents.