高压电缆接地电流的计算及其影响因素分析

Calculation and analysis of grounding current and its influence factors of high-voltage power cables

单芯高压电缆金属护套接地电流过大会导致其护套上产生大量附加损耗,降低电缆载流量,缩短电缆使用寿命。为分析电缆线路金属护套中的接地电流,建立了单芯电缆交叉互联接地方式下接地电流的数学计算模型,并编制了相应的计算程序,通过与实测值比较,验证了该计算程序能准确得到实际电流值。在此基础上,分析了单芯高压电缆金属护套接地电流与其接地电阻、护套参数以及大地电阻率等影响因素的关系。结果表明,电缆接地电阻对接地电流的影响较大;在工程实际范围内,金属护套参数对接地电流值影响不大;只有当大地电阻率很低时,接地电流值才对大地电阻率比较敏感。研究结果为高压电缆运行维护提供了理论依据。

Excessive grounding current on metal sheath of single-core high-voltage cable will bring massive additional loss to the cable, which reduces the cable′s current-carrying capacity and safe operation lifetime. In order to analyze the grounding current in metal sheath, a mathematical model of grounding current calculation and relevant program are established aiming at single-core high-voltage cables in cross-bonding grounding mode. The calculation results prove that the program is competent to reflect actual grounding current. Furthermore, the relationship between grounding current and its influencing factors such as grounding resistance, sheath parameters and earth resistivity is analyzed. The results of analysis indicate that the grounding resistance has a great influence on the grounding current, while in actual engineering the parameters of metal sheath do not. Grounding current is sensitive to earth resistivity only when the value of earth resistivity is low. The research conclusions provide a theoretical basis for the operation and maintenance of high-voltage cables.