三相五柱变压器空载直流偏磁的计算分析

Calculation and Analysis of No-load DC Bias of Three-phase Five Column Transformer

由于地磁暴在大地产生感应电流以及直流输电系统单极性运行方式与大地形成回路,使得直流电流进入变压器中性点,造成变压器直流偏磁,电流发生畸变,产生谐波。文中在已经研究过的单相特高压变压器直流偏磁计算的基础之上,以230 kV三相五柱式变压器为例,依据单相变压器和三相变压器电路、磁场的区别,利用变压器磁场模型与电路模型建立微分方程,对三相变压器的直流偏磁进行了计算分析。为使计算结果能够快速稳定,在电路中人为串联大电阻,并在计算完成后使用电压补偿的方法将串联电阻所分电压补偿在电路中,根据计算结果可知,电压补偿可以较好的消除由于串联电阻所带来的波形偏移现象,补偿后的结果可以较好的分析三相五柱变压器直流偏磁现象,为三相五柱变压器的直流偏磁耐受能力及其变压器保护提供了参考。

Due to the induction current generated by geomagnetic storm in the earth and the loop formed between the monopolar operation mode of DC transmission system and the earth,it makes the the DC current enter into the neutral point of the transformer,causes the DC bias,the current distortion and harmonic generation of transformer.In this paper,the 230 kV three-phase five column transformer is taken as an example on the basis of calculation of DC bias of single-phase UHV Transformer which has been studied.The differential equation is set up in accordance with the difference between the circuit and magnetic field of single-phase and three-phase transformer and by the use of magnetic filed model and circuit model of the transformer to calculate and analyze the DC bias of three-phase transformer.In order to make the calculation results fast and stable,the large resistance is artificially connected in series in the circuit and,after completion of calculation,the voltage compensation method is used to compensate the voltage divided by the series resistance in the circuit.It is known by the calculation results that the voltage compensation can better eliminate the waveform migration caused by the series resistance,and the result after compensation can analyze the DC bias of three-phase five column transformer and can provide a reference for DC bias withstand capability and protection of three-phase five column transformer.