高压直流挤包绝缘海陆复合电缆温度场及空间电荷分析

Analysis on Temperature Field and Space Charge of High-voltage DC Extruded Insulated Submarine-land Composite Cable

高压直流电缆运行过程中会在绝缘层内产生空间电荷,导致电场畸变,甚至绝缘击穿。为了研究电缆实际运行中空间电荷的影响,本研究利用有限元仿真获得了高压直流海陆复合电缆在额定电流、最大稳态电流和短时过载电流情况下的温度场。根据仿真结果,在空间电荷测试中分别设置10、20、40℃的温度差,分别模拟400 kV高压直流电缆在不同工作条件下的温度场。结果表明:在额定电流下XLPE绝缘层两侧温度差为8.1℃;最大稳态电流下XLPE绝缘层两侧温度差为18.7℃;短时过载1 h情况下,XLPE绝缘层两侧温度差为61.1℃;短时过载36 h情况下,XLPE绝缘层两侧温度差为41.1℃。实验结果显示温度梯度会使XLPE阳极低温侧产生异极性电荷积聚,使电场发生畸变。通过对畸变电场进行校正计算,发现最大电场畸变率随平均场强呈线性关系。随着温度梯度的增加,电场畸变率也在增大。在温度梯度40℃和外施场强50 kV/mm下,最大电场畸变率为1.68。

During the operation of high-voltage DC cables, space charge generates in the insulation layer, it leads to electric field distortion and even insulation breakdown. In order to study the effect of space charge in the actual operation of cable, we obtained the temperature field of high-voltage direct current submarine-land composite cable under the conditions of rated current, maximum steady-state current, and short-term overload current,respectively. According to the simulation results, the temperature difference in the space charge test was set as10℃, 20℃, and 40℃, respectively, and then the temperature field of 400 kV high-voltage DC cable under different condition was simulated. The results show that the temperature difference between the two sides of XLPE insulation layer is 8.1℃ and 18.7℃under rated current and the maximum steady-state current, respectively;while the temperature difference is 61.1℃ under the short-term overload for 1 hour;and that is 41.1℃ under short-term overload for 36 hours. The experimental results show that the temperature gradient enhances the accumulation of heteropolar charge at the low temperature side of positive pole of XLPE, which leads to the distortion of electric field. Through the correction computation of the electric field distortion rate, it is found that the maximum electric field distortion rate has a linear relationship with the average electric field strength. With the increase of temperature gradient, the electric field distortion rate also increases. The maximum electric field distortion rate is1.68 under the temperature gradient of 40℃ with the applied electric field of 50 kV/mm.