Study On The Characteristics Of Space Charge At The Interface Of Cable Insulation

With the development of urban construction,the replacement of overhead lines by cable lines has become an inevitable trend.As a commonly used cable variety,XLPE cable has excellent electrical and heat resistance properties.It has been widely used in urban power distribution networks.Affected by factors such as electric field and temperature during long-term operation,space charges will appear in the cable,especially the space charge is more likely to accumulate at the composite insulation interface composed of DC cables and accessories.The accumulation of space charges in the insulation layer can result in the deformation of the partial field and destroy the microstructure of the insulation material.With the destruction of the microstructure,more space charges can accumulate in the cable,which eventually causes the insulation performance to be gradually destroyed.The cable load operation causes the insulation layer to form a high temperature gradient inside and outside,and the existence of the temperature gradient will affect the space charge behavior of the double-layer dielectric.Therefore,this paper studies the cable’s main insulation Cross-linked Polyethylene(XLPE)and accessory stress cone insulation silicone rubber(SR)and XLPE and accessory insulation Ethylene Propylene Diene Monomer(EPDM)The space charge characteristics of the double-layer dielectric flat specimens under different DC electric fields and different temperature gradients are designed to improve the interface space charge characteristics of XLPE cable insulation and accessory insulation.This provides a theory for the insulation design of DC cables and accessories.And application value.This paper designs and builds a space charge measurement device that can achieve temperature gradients,prepares XLPE/SR and XLPE/EPDM double-layer dielectric flat specimens,and performs space charge measurements on flat specimens under the synergy of temperature gradient field and DC electric field.Finally,based on Maxwell-wagner theory and bipolar charge transport model,the interface charge simulation of XLPE/SR double-layer dielectric.the result shows:The interface space charge has the same polarity as the accumulated charge on the medium side with high conductivity.The amount of space charge accumulated at the XLPE/EPDM interface is less than that of the XLPE/SR double-layer medium,and the space charge accumulation in the double-layer medium is significantly affected by temperature gradients.Influence,as the temperature gradient increases,the migration of heteropolar charges becomes more pronounced,causing more space charges to accumulate at the interface.Based on the M-W polarization model,the space charge distribution inside the XLPE/SR double-layer dielectric at low field strength(5kV/mm)can be simulated more accurately.However,under high field strength(10kV/mm and 15kV/mm),the bipolar charge transport model is more suitable for simulating and calculating the interface charge density of the double-layer dielectric.