特高压直流对500kV变压器直流偏磁的影响分析

直流系统单极运行时会在周边变压器中引起直流偏磁,以江苏苏北电网±800 k V晋北—南京、±800 k V锡盟—泰州、±800 k V陇彬—徐州特高压直流工程为例,研究其对500 k V变电站直流偏磁的综合影响。兼顾各接地极附近土壤情况,采用综合水平多层土壤模型,建立了苏北电网直流系统模型,对单条或多条直流线路同时单极运行时附近变电站的偏磁电流进行仿真分析。结果表明:土壤电阻率越大,距离接地极同一位置处地电位越高;多条直流线路同时单极运行时主变偏磁电流数值等于各单条直流线路单极运行时的代数和;相邻变电站的抑制措施应综合考虑。

Influence of HVDC Systems on 500 kV Transformer DC Magnetic Bias

DC magnetic bias current will be caused in transformers when HVDC systems operating in mono-pole situation. The combined influence on DC magnetic bias of 500 kV transformers is researched, taking ±800 kV Jinbei-Nanjing, Ximeng-Taizhou and Longbin-Xuzhou in northern Jiangsu for example. A comprehensive horizontal multilayer soil model is adopted, considering different soil conditions adjacent to different ground electrodes, based on which the DC system model of northern Jiangsu is built. The DC magnetic bias currents in substations nearby are analyzed when one or more in three HVDC power transmission lines are operated in monopole operation mode. Simulation results show that the greater the soil resistivity, the higher the earth surface potential; when multi HVDC lines are operated in monopole mode simultaneously, the value of DC current is equal to algebraic sum of the DC current of each HVDC line solely operated in monopole mode; the restraining measures of adjacent transformers should be considered comprehensively.