XLPE水树老化电缆介电响应下非线性研究

Research of Nonlinear Dielectric Response of Water Tree-aged XLPE Cable

为了准确评估XLPE电缆的绝缘状态,利用极化-去极化电流法对不同水树长度电缆进行测试,并研究XLPE水树电缆介电响应时的非线性特性。通过测得的极化-去极化电流曲线及扩展Debye模型,对XLPE电缆的介质损耗因数(tanδ(0.1 Hz))和直流电导率(σ)进行计算,利用tanδ(0.1 Hz)和σ随电压变化趋势来反映XLPE电缆非线性特征,并分析了其非线性特征与水树电缆老化状态的关系。结果表明:水树电缆在时域的去极化电流和介质损耗因数在频域的低频段都表现出非线性特征,在频域下tanδ(0.1 Hz)的非线性特征比时域下σ的非线性更明显;XLPE水树电缆具有明显的从线性到非线性的转折电压,水树长度越长转折电压越低。上述特性可用于对XLPE老化电缆是否存在水树和水树严重程度进行判断。

In order to evaluate the insulation condition of XLPE cables accurately, XLPE cables with water trees of different lengths were test by polarization-depolarization current method, and their nonlin- ear dielectric response properties were studied. The dielectric loss factors and DC conductivity of the cables were calculated through the measurement of polarization-depolarization current curve and the expan- sion of Debye model. The trends of tan6（0.1 Hz） and DC conductivity（a） Changing with voltage were used to reveal the nonlinear properties of XLPE cables, and the relationship between the nonlinearity and the ageing state of water tree-aged cables was analyzed. The results show that the depolarization current in the time domain and dielectric loss factor in the low frequency domain have nonlinear characteristics. The nonlinearity of tan^（0.1 Hz） in frequency domain is more obvious than that of a in time domain. There is an obvious transition voltage of water tree-aged cable turning from linear to nonlinear, and it reduces with the increase of the length of water tree. These features can be used to assess the existence of water tree and its order of severity in XLPE cable.