挤包绝缘高压直流电缆制造与应用中的径向梯度效应

挤包绝缘高压直流电缆在直流输电工程中应用广泛，但制造与应用中的梯度效应显著影响其直流电气性能。以500 kV交联聚乙烯直流电缆为研究对象，首先，通过仿真计算理想均匀绝缘电缆中的场强分布；然后，计算交联和脱气过程中绝缘层的温度分布，并对电缆绝缘切片取样，测量不同径向位置绝缘的相态结构和直流电气性能；最后，根据实测电导率对电缆绝缘中场强分布进行仿真。结果显示：电缆绝缘在交联和脱气过程中存在温度梯度，绝缘的相态结构和直流电气性能在径向上分布不均匀，绝缘电导率在径向上的梯度分布导致电缆绝缘中场强均呈现出内低外高的分布规律，且最外侧绝缘的场强大于均匀绝缘中的最高场强。

The Radial Gradient Effect of HVDC Extruded Cables in Manufacturing and Application

Extruded cables are widely used in HVDC projects,but the gradient effect in manufacturing and application affects their DC electrical performance significantly.The 500 kV XLPE DC cable was studied in this paper.Firstly,the field strength distribution in the uniformly insulated cable was simulated.Secondly,the temperature distribution of the insulation in the process of cross-linking and degassing was calculated,and the phase structure,by-product content and DC electrical performance of the insulation of cable at different radial positions were also measured.Finally,the field strength distribution of the insulation was simulated.The results show that there is a temperature gradient of cable insulation in the process of cross-linking and degassing,and the phase structure,and DC electrical properties of the insulation are non-uniformly distributed in the radial direction.The gradient distribution of the insulation conductivity in the radial direction results in the distortion of the field strength,in which the field strength of outer layer of insulation is greater than that of inner layer,and the field strength of the outer layer of insulation is greater than that the maximum electric strength in the uniform insulation.