Research On Electrical Tree Aging Characteristics Of Cable Based On UHF-Ultrasonic

For urban transmission and distribution power grids at home and abroad,underground power cable lines has been widely used to instead the overhead transmission lines.The XLPE(Cross Linked Polyethylene)insulated power cable has been widely used due to its excellent performance.The degradation process of XLPE power cable is very complicated.According to research and operational experience,electrical treeing is the main factor affecting the long-term safe operation of XLPE power cable.Therefore,it is in urgent to study the law and mechanism of the electrical trees of XLPE power cable.The main research contents are as follows.Firstly,a joint detection system is established to detect the partial discharge signal of the cable online without affecting the normal operation of the cable.The interference of the environment is effectively removed by using the combination of hardware and software.The detection system lays a good foundation for measuring the partial discharge signal of electrical trees.Then,through thermal aging and electrical tree needle-plate experiment system,the rules affcting the electrical trees is studied when the 10 kV XLPE cable has different defects and thermal aging time.The partial discharge signals caused by electric trees under different influence factors in such experiment was compared and the mechanism of these influencing factors was analyzed.The experimental results show that defects and aging degree have obviously regular influence on the initiation characteristics of electrical trees.The local defect will reduce the initiation time of the electrical trees and increase the discharge signal of the electrical trees.With the expansion of the defect,the influence is gradually increased.Meanwhile,with the increase of thermal aging time,the insulation property of XLPE will be decreased,and the trigger time of the electrical trees will be reduced and the discharge signal will be increased as well.