The Space Charge Characteristic of Cross-Linking Polyethylene Insulation of High Voltage DC Cables on Different Voltage Levels Under Temperature Gradient

Abstract

For the purpose of researching the space charge properties and electric field distribution of HVDC cross-linking polyethylene cables at various voltage levels under temperature gradients (TG). In this study, a 2D flat structure model and a 2D coaxial structure model with the same thickness were created using COMSOL with the bipolar charge transport model. Comparison and analysis were done on the impacts of temperature gradient and coaxial structure on electric field and space charge distribution. Simulated space charge distribution in the radial direction of XLPE cables for HVDC cables operating at voltages of 100 kV, 160 kV, 250 kV, 320 kV, and 500 kV and the electric field distortion of cathodes and anodes of coaxial cables under temperature gradient were compared and analyzed. According to the study's findings, the rate of change of the electric field increases progressively as the voltage level rises, the electric field change rate of the outer semiconducting layer increases from 29.93% to 65.72% when the temperature difference is 40 ºC. For the main insulation of cables of the same voltage level, because of the coaxial construction and temperature gradient, more homocharges will build up at the outer semiconducting layer than they will near the conductor, increasing the electric field change rate there relative to that near the conductor. When the temperature difference is 40 ºC, the electric field change rate of the outer semiconducting layer of the 500 kV XLPE cable can increase to a maximum of 65.72%.