电树枝对10 kV电缆阻抗谱影响机理及其定位方法研究

Influence Mechanism of Electrical Tree on Impendence Spectrum of 10 kV Cables and Their Location Method

电树枝是电力电缆中常见的绝缘劣化类型,电树枝的生长会引发绝缘材料性能的改变,从而威胁电缆的安全运行。而传统的检测方法往往无法实现对电缆内微小电树枝劣化区域的有效检测。本研究选用10 kV单芯交联聚乙烯(XLPE)电缆,在其绝缘中引入电树枝缺陷并测量了不同树枝生长阶段的绝缘电导率、内外半导电层间等效电容数值,采用宽频阻抗谱测量及傅里叶逆变换方法对设定的电树枝劣化区域进行测量及定位。结果表明:电树枝的生长使电缆绝缘电导电流明显提高,电树枝累积损伤的增加使内外半导电层间电容值增大,由于电导及电容数值的变化,使电树枝劣化段的波阻抗畸变。应用宽频阻抗谱及傅里叶逆变换方法实现了对于电树枝劣化区域的准确定位,同时电树枝的不同生长阶段会影响阻抗谱及傅里叶逆变换谱图中畸变点的幅值。

Electrical tree is a common type of insulation deterioration in power cables.The growth of electrical trees will change the performance of insulating materials,thereby threatening the safe operation of cables.However,traditional detection methods are often unable to realize effective detection of the tiny electrical trees deteriorated area in cable.A 10 kV single-core cross-linked polyethylene(XLPE)was selected,and electrical tree defects were introduced into its insulation.The insulation conductivity and equivalent capacitance between the inner and outer semiconducting layers at different growth stages of electrical trees were measured,and the electrical trees deteriorated area was tested and located by broadband impedance spectroscopy and inverse Fourier transform method.The results show that the growth of electrical trees increases the conduction current of the cable insulation significantly.The increase of electrical tree cumulative damage makes the capacitance value between the inner and outer semiconducting layers increase.Due to the change of conductivity and capacitance,the wave impedance of the electrical tree deteriorated area distorts.Using the broadband impedance spectroscopy and inverse Fourier transform methods can realize the accurate location of the electrical tree deteriorated area.At the same time,the different growth stages of electrical tree will significantly affect the amplitude of distortion points in the impedance spectroscopy and inverse Fourier transform spectrum.