抑制变压器直流偏磁的电流注入法

A Current Injection Method to Restrain Transformer DC Bias

针对直流输电单极大地运行方式下变压器直流偏磁的问题,提出中性点注入直流电流的抑制方法,并建立了电网的直流网络模型,分析了该方法的原理。通过仿真和实测数据的对比,验证了模型的有效性,并定量分析了土壤电阻率和补偿距离对补偿度的影响。仿真计算和广东义和变电站的实际应用情况表明:电流注入实质上起补偿变电站间母线电位差的作用,土壤电阻率增大或者补偿距离减少会导致注入电流增加,补偿度降低,在一般情况下补偿度小于0.6。最后以罗洞站抑直方案为例,验证了电流注入法不适用于复杂运行方式的变电站,并提出了解决方案。

Current injection method for transformers＇ DC bias under HVDC transmission ground return mode is presented. A DC network model of a power grid is set up to analyze the mechanism behind the proposed method. By comparison between simulation and measurement, validity of the method is checked and the impact of soil resistivity and compensation distance on compensation degree is analyzed. Simulation and application of the method in Yihe Substation shows that： the method actually functions as potential difference compensation to the bus of substation; higher soil resistivity demands longer compensation distance and higher injection current, but it leads to lower compensation degree and the compensation degree usually bellows 0.6. At the end, the example of Luodong Substation is listed to verify that current injection method is not applicable to substations under complex operation mode, then another solution is brought up.