高压直流电缆附件XLPE/SIR材料特性及界面电荷积聚对电场分布的影响

Interface charge accumulation between double-layer dielectric is the key factor causing interface discharge of the high voltage direct current (HVDC) cable accessory. In this paper, the dielectric properties, conductivity and thermal conductivity of XLPE and SIR were measured. The charge accumulation properties of the XLPE/SIR interface and the variation of internal electric field caused by local electric field distortion were studied. The experimental results show that as the temperature increases, the conductivity of XLPE increases significantly, while the conductivity of SIR increases relatively slowly. The mismatch of the conductivity of the two materials at high temperature is an important reason for the interface charge accumulation. At room temperature, the negative charge at the XLPE/SIR interface is about 3.42×10^-4C/m², which will enhance the electric field of the cable main insulation and weaken the electric field distortion at the root of the stress cone. Electric field of the main insulation increases about 36% and the electric field distortion at the stress cone root decreases about 62%. When the temperature exceeds about 36℃, positive charges begin to accumulate at the interface of XLPE/SIR. As the temperature increases, polarity reversal phenomenon occurs, which leads to aggravation of the local electric field distortion at the root of stress cone, and the maximum distortion electric field reaches 12kV/mm at 70℃.