Space Charge Characteristics of XLPE/EPDM Interface Under DC Superimposed Impulse Voltage

AmongDC transmission lines, cable line is susceptible to operation overvoltage and lightning overvoltage, which causes the line to superimpose impulse voltage on DC voltage. In addition, the inductance/capacitance effect of power equipment insulation leads to the electromagnetic energy conversion process between the components that causes the line system to oscillate, generating hundreds to thousands hertz high-amplitude impulse voltage waves. These situations seriously impair the long-term reliability of power equipment insulation.Consequently, the space charge of XLPE/EPDM composite sample under DC voltage, impulse voltage and DC superimposed impulse voltage was measured based on DC superimposed impulse voltage PEA measurement system in laboratory. Experimental results show that, under DC voltage, conductivities of two media are reversed which causes gradual change of interface with the increase of electric field; under impulse voltage, positive voltage causes accumulation of negative charge at the interface, negative voltage causes accumulation of positive charge at the interface, and the amount of charge increases with the increase of electric field. When DC superimposed same polarity impulse voltage is applied, the equivalent DC voltage field is multiplied and space charge at the interface decreases first and increases in opposite direction due to the reversal of two material's conductivities. When DC superimposed opposite polarity impulse voltage is applied, space charge at the interface decreases due to the decrease of equivalent DC voltage field and transient electric field polarization in the superposition period. © 2022 Science Press. All rights reserved.