绝缘层厚度对高压直流电缆电场和温度场分布的影响

The distribution of electric and temperature fields in high voltage cables is a key factors in the design of insulation thicknesses. In the study, an electric -thermal coupling simulation model of high-voltage direct current (HVDC) cable was established, and the changes of resistivity and thermal conductivity of cable insulation layer and semi-conducting layer with temperature were measured and analyzed. The influence of insulation layer thickness on the distribution of cable electric and temperature fields was calculated. The influence of load capacity and laying method on the temperature field distribution of cable with different insulation layer thickness was discussed. Experimental results show that the XLPE resistivity decreases by 2-3 orders of magnitude with increasing temperature (25-90°C), while the semi-conductive shield increases from 21.4Ω·cm to 75.5Ω·cm. Overall, the thermal conductivity of semi-conducting layer is about twice that of insulation layer. When the insulation thickness is increased from 20 mm to 35 mm, the electric field inside the insulating layer is reduced by about 34%. The temperature difference between inside and outside the insulation layer increases by about 54%. The temperature difference of the insulation layer increases from 3.5°C for 800A to 31.4°C for 2400A with the increase of the amperage. The heat dissipation efficiency of the three laying methods in descending order is tunnel laying, directly buried laying and pipeline laying.