交联聚乙烯电缆在线绝缘诊断新方法研究

研究目的:交联聚乙烯(XLPE)电缆有广泛的适用范围,研究其绝缘早期劣化检测方法对于延长电缆寿命有着关键的作用。研究方法:建立了水树精确数字仿真模型,提出一种新的在线绝缘诊断方法:高频信号叠加法。在电缆屏蔽层叠加高频低幅电压信号,以凸现损耗电流波形,利用分形方法对采集到的损耗电流信号进行分析。研究结果:XLPE电缆的水树的劣化使得损耗电流中谐波分量增加。谐波分量主要由于水树的非线性电压-电流特性引起。谐波分量的出现使损耗电流信号的分形维数增加。本文分别计算了容量、信息、关联3种维数,分析了各种维数和水树劣化之间的内在联系。研究结论:分形维数很好地反映了电缆中水树劣化的程度,可以作为在线绝缘水树劣化的诊断依据。

Research on the New Hot-line Monitoring Method of XLPE Power Cable

Research purposes: XLPE cables can be widely used in various places.Early degradation of XLPE cables researches may extend its using life.Research methods:In this paper,an accurate water tree model has been created.We have successfully developed a new hot-line diagnostic method called "high frequency superposition method".We superpose a voltage with high frequency but low amplitude on the shielding layer of power cables to make the loss current more obvious.Then we use fractal methods to analyze loss current signals collected.Research results:Degradation of XLPE cable by water trees gives rise to harmonics in the loss current.Harmonic components arise as a result of nonlinear voltage-current characteristic of water trees.The fractal dimension of loss current waveform increases because of the growth of harmonics.We calculate 3 fractal dimensions including capacity,information and correlation.We discuss the interrelationship between fractal dimension and harmonics.Research conclusions:The fractal dimension provides an extremely good indication of the state of degradation,which can be used as a judgment for hot-line dielectric degradation.