XLPE High-voltage Cable Insulation Monitoring And The Experimental Research

With the development of electrical power construction, XLPE cable was widely used with its superior electric performance and heat resistance. But as the increasing of cable and the extension of running time, the cable's faults become more and more frequently. Since the 1980s, a variety of online monitoring methods have been developed to monitor insulation aging of the cables. However, to a certain extent, these methods have their limitations. Thus, they are not conducive to the large-scale popularization. On the basis of a comprehensive analysis of various online monitoring methods, this paper aims to propose a new online monitoring method for insulation, the characteristic signals of which can be easily separated from those undesired signals.Moreover, this monitoring method shows high accuracy.This paper analyse XLPE cable insulation failure, water-tree degradation is considered the main cause of XLPE cable breakdown after incipient failures such as bad terminals and joints and some mechanical damages are ruled out. This paper analyses the growth process of water tree from point of view of microcosmic, summarized the characteristics of water tree, summed up the faetor to form water tree. According to the characteristics of XLPE cable ,it proposed to use low frequency signal to detecte cable insulation situation. This paper obtained the advantages of using low-frequency signals to detect water tree that be more sensitive reflect water tree aging condition by theoretical and experimental analysing. This paper has artificially cultured a few different aging water tree cables and then verified the above conclusion by analysing the test results. Meanwhile this paper has proposed two main sources of low-frequency signals: the low-frequency signals generated by AC Superposition Method and the inherent low frequency signals of the power system. Though theoretical analysis and simulation analysis of the former one, this paper has concluded that the method can generate the required low frequency signals and the frequency has a fixed value, therefore, they are easily removed interference. The latter one still needs to do a lot of study for application because of the uncertainty of the signals.