基于拓展传输线理论的高压交流电缆输入阻抗和金属护套电压计算分析

Calculation and Analysis of Input Impedance and Sheath Overvoltage on High Voltage Alternating Current Cable Based on Extended Transmission Line Method

基于电缆外部精确电磁场分析方法,提出了一种拓展传输线理论,能够计及广义大地参数和电磁暂态仿真的影响计算电缆输入阻抗。采用电磁暂态仿真程序EMTP-RV,利用拓展传输线理论对典型高压交流电缆开展输入阻抗和金属护套电压特性研究,研究当合闸于空载电缆时的金属护套暂态电压特性;通过对正序激励下的电缆输入阻抗模值-频率响应进行研究,分析由三相金属护套交叉互联产生的多种传播模态。采用拓展传输线理论计算的结果与使用基于矩量法的改进数值电磁场分析方法(method of moments-surface admittanceoperator,MoM-SO)的计算结果基本拟合,与现有电磁暂态仿真软件中(ATP-EMTP、PSCAD/EMTDC和EMTP-RV)的CableConstants子程序计算结果出现显著性差异。当合闸于空载电缆线路时,受大地电阻率影响,采用Cable Constants子程序计算出的电缆金属护套最大暂态电压与采用拓展传输线理论所得出的结果相比,计算偏差位于1.8%至135%之间。考虑输入阻抗计算和暂态仿真的关键性差异,研究内容对今后开展高压交流电缆参数计算、模态分析、电磁暂态仿真、过电压研究具有参考意义。

This paper introduces a comprehensive analysis of the input impedance and sheath voltage of a high voltage alternating current(HVAC)cable using EMTP-RV.A novel extended transmission line method is employed to calculate the impedance and admittance of the cable,based on a precise external electromagnetic analysis that considers the impact of general earth parameters on input impedance and transient characteristics.The study explores the amplitude-frequency response of the cable’s input impedance when excited by positive sequence and modes,delving into the analysis of mixed propagations arising from cross-bonded sheath configurations.In the context of transient simulation,the paper investigates the transient voltage of the sheath through the energization of an unloaded cable.Comparisons between results obtained through the extended transmission line method and the modified method of moments-surface admittance operator(MoM-SO)reveal a strong agreement,while significant discrepancies are observed when employing Cable Constants in tools such as ATP-EMTP,PSCAD/EMTDC,and EMTP-RV.Particularly noteworthy are the findings related to cable energization under unloaded conditions.The influence of earth resistivity prompts a comparison of maximum transient voltages on the sheath,calculated using the Cable Constants sub-routine versus the extended transmission line method.Deviations between the two methods range from 1.8%to 135%.The implications of these results suggest that the contents of this paper can serve as a reference for future investigations into parameter calculations,modal analysis,and transient voltages of HVAC cables.