高压直流挤包绝缘电缆系统试验的分析和研究

与高压交流挤包绝缘电缆系统的试验相比,高压直流挤包绝缘电缆系统试验需要考虑电缆绝缘内最大温差和叠加冲击电压试验这两个难点。直流电缆制造商会依据绝缘材料和电缆设计特点,向试验机构提供绝缘内最大温差的数值。在负荷循环的稳态过程中,需要控制绝缘内最大温差。由于在试验过程中没有办法直接测量绝缘内最大温差,其数值是通过稳态热传递原理公式推算得到的。对依据稳态热传递原理推算的绝缘内最大温差和负荷循环的执行情况进行了说明。运行中的高压直流输电线路除了承受正常的工作电压外,同时还可能承受雷电和操作冲击的作用。因此,在高压输电线路的绝缘设计中,需要考虑直流高压下的空间气隙的冲击放电特性,并对叠加冲击电压试验进行研究。对叠加冲击电压试验的两种试验回路进行了分析和探讨。

Analysis and Discussion of Testing on High Voltage Direct Current Extruded Power Cable System

Compared to the testing for high voltage alternate current extruded cable system,high voltage direct current extruded cable system testing needs to consider two unique test requirements,that’s the maximum temperature differ ence over the cable insulation in steady state and superimposed impulse voltage test.The maximum temperature differ ence over the insulation is provided for testing body by adirect current cable manufacturer depending on insulating ma terial and a cable design.The maximum temperature difference over the insulation needs to be controlled during a steady state of a load cycle.In practice,it is not possible to measure the maximum temperature difference over the in sulation directly during the test.By applying of steady state heat transfer theory,a formula is introduced to calculate the maximum temperature difference over the insulation.This paper introduced the procedure of calculation of the maximum temperature difference over the insulation based on the steady state heat transfer theory and execution of a load cycle.The high voltage direct current power transmission line in service needs to withstand normal operating volt age.In the meantime,the high voltage direct current power transmission line will also be subjected to lightning and switching strikes.Therefore,while doing the insulation design for the high voltage direct current power transmission line,the lightning discharge properties of the air gap under the high voltage direct current needs to be considered and the study for the superimposed impulse voltage test needs to be done as well.This paper analyzed and discussed two kinds of testing circuits for superimposed impulse voltage test.