Study On Insulation Detection Of XLPE Cable Based On Polarization/Depolarization Current Method

Cross-linked polyethylene(XLPE)cables are widely used in today’s urban distribution networks due to their superior mechanical and electrical properties.However,due to the impact of harsh environments such as high temperature and humidity,the cables laid underground will have different degrees of aging,thereby threatening the safe operation of the power grid.Therefore,testing the insulation status of XLPE cables and analyzing their insulation aging characteristics have become an important basis for ensuring the safe and stable operation of power systems.Traditional detection methods such as insulation resistance method and AC/DC withstand voltage method have the disadvantages of less information and greater destructiveness.In recent years,an emerging polarization/depolarization current(PDC)method has been used as a non-destructive dielectric response method is getting more and more attention.The PDC method can effectively evaluate the aging state of the cable insulation by characterizing the polarization and conductivity of the cable insulation.On the basis of summarizing the PDC testing method,a set of testing instrument based on polarization/depolarization current method is developed..The device is mainly composed of DC high-voltage power supply,XLPE cable,weak current amplifier,high-voltage relay,intermediate relay,data acquisition card,metal shielding box,etc.After each module is assembled and debugged,it is connected to the host computer,and the design of the detection software is completed by using the LAB VIEW platform to realize the functions of current data collection,current filter processing and measurement mode switching.In this paper,the cable is put into an aging test box to change its aging time,aging temperature and other test conditions.It has completed more than 500 hours of aging test and obtained cable test samples under different aging conditions.Then connect the cable sample to the built detection device,and use the LAB VIEW platform to complete the current data collection work and obtain a large amount of precious test data.Finally,the polarization/depolarization current waveforms that characterize the aging characteristics are compared and analyzed and the basic aging characteristics of cable insulation are summarized.Then the concept of aging factor is introduced,an extended Debye model of cable insulation is established,and MATLAB simulation is performed.The final simulation results are basically consistent with the experimental test data.