直流大地运行时交流系统直流电流分布的预测方法

Estimation of DC Current Distribution in AC Power System Caused by HVDC Transmission System in Ground Return Status

直流输电线路在系统调试或发生故障情况下,会处于单极大地回路电流运行方式。当直流输电系统的大地回流很大时,可能造成部分交流输电系统中的变压器处于偏磁状态。该文提出了分析直流大地运行时交流系统直流电流分布的数值方法。该方法使用矩量法分析复杂大地结构中由直流接地极、交流变电站接地网及其它埋地金属管道构成的多接地系统所产生的地中电流场。同时将电路理论与矩量法相结合,从而将多接地系统与地上交流输电网络联系起来。分析了贵广直流输电线路以大地为回路运行时,直流电流在广东春城变电站周围220kV及以上电网的分布,并与现场测试结果作了比较。

The HVDC transmission system maybe operated in ground return status when the system is in debug or failure. If the ground return current of the HVDC system is large enough, some transformers in AC system may be under DC bias. In this paper, a numerical method is presented to calculate the DC current distribution in AC power system caused by a HVDC system. The method of moments is Used to calculate the electric fields in complex earth structure caused by all the grounding systems including the DC grounding electrodes, the AC substation grounding systems, and the long metal pipe lines. The circuit equations are coupled to the moment method to combine the AC transmission lines with the grounding systems.Current distribution of the power system above 220 kV around Chuncheng substation in Guangdong province is analyzed when the Gui-Guang HVDC system is in ground return status. The results are compared with those of testing on site.