500kV XLPE海底电缆绝缘及护套暂态电压仿真计算

Simulation Calculation of Transient Voltages on Insulation and Sheath Along 500kV XLPE Submarine Cable

舟山500 kV联网工程将是世界上首条敷设500 kV交联聚乙烯（XLPE）海底电缆的架空线–电缆混联输电线路。针对500 kV XLPE海底电缆系统绝缘配合问题,基于舟山混联输电线路,应用PSCAD/EMTDC软件建立了全线路系统仿真计算模型,并分析了电缆两端及中间接地体的建模问题,计算了海底电缆绝缘和外（绝缘）护套上各类暂态电压特性及其分布。计算结果和研究分析表明：操作空载线路在电缆绝缘上可产生最高约800 kV的操作暂态电压,通过断路器加装合闸电阻可有效限制操作暂态电压在500kV以下,而最大雷电流（100 k A）直击线路时,电缆绝缘上的雷电暂态电压达到1 230 kV;电缆外护套上产生的最大暂态电压均出现在电缆长度的中间段,雷电直击架空线路时达到11.4 kV,各种操作暂态电压最高达6.45 kV,而最大短路电流为35.6 k A时工频感应电压有效值达到3.04 kV;各种暂态电压下电缆的绝缘配合均满足500 kV电缆标准要求。该研究结果为500 kV XLPE海底电缆的绝缘设计及工程应用中的绝缘配合提供了必要的基础。

The first transmission lines combined with 500 kV XLPE submarine cable and overhead line in the world will be adopted in the Zhoushan 500 kV power network project. In order to proofread the insulation coordination of 500 kV XLPE submarine cable system, we established the models of simulation calculation with the PSCAD/EMTDC software based on this project, and analyzed the modeling process specifically for the grounding body at terminals and the middles of cables. Moreover, the characteristics and distributions of various transient voltages on the insulation and sheath（insulation） of the cable were calculated. The calculation and analysis results show that the transient voltage on the cable insulation caused by switching on a no-load line can reach 800 kV, which will be effectively limited to 500 kV by the installation of the closing resistor of circuit breaker, and the highest transient voltage on the cable insulation caused by the worst lightning striking to the overhead line with the highest current of 100 k A is 1 230 kV. The results also indicate that the maximum lightning induced transient voltage on the sheath tends to locate at the middle of the cable length, and can reach 11.4 kV, the maximum induced switching transient voltage on the sheath can be 6.45 kV, and when the maximum short-circuit current of 35.6 k A occurs in the cable lines, the induced power frequency voltage on the sheath will be 3.04 kV（rms）. The insulation coordination can meet the standard specifications of 500 kV XLPE cable. The research can provide a necessary reference for the insulation design of 500 kV submarine cable and its engineering application.