【摘要】 近年来随着我国电网电压等级的升高,电网规模的扩大,地磁活动引起的电网异常现象引起了人们的关注。对于频率一般为0.1~0.001Hz的地磁感应电流,电网计算模型采用直流等效原则,即地面感应电势等效为直流电源,系统元件等效为电阻,忽略电感。但地磁感应电流频率的变化影响变压器的偏磁程度,从而影响地磁感应电流计算的精确度。采用时域场路耦合法,建立变压器模型,利用磁场模型计算动态电感,电路模型求解电流,分析不同频率下变压器动态电感和励磁电流的数值波形,确定其偏磁程度。结果表明,当中性点之间的地面感应电势(ESP)一定时,频率为0.1~0.002Hz时变压器并未饱和,GIC若按照直流计算存在不同程度的误差,频率越低误差越小;频率低于0.002Hz时变压器饱和,可按直流进行计算。更多还原

【Abstract】 Recently as power grid voltage level rises in China and with the expansion of the grid,some abnormal phenomena of the power grid caused by geomagnetic activities have aroused great concern. As for the geomagnetic induced current( GIC) whose frequency generally ranges from 1Hz to 0. 001Hz,the grid computing model usually adopts DC equivalent principles,namely the earth surface potential( ESP) being equivalent to the DC power supply,system components being equivalent to resistors,and inductance being ignored. But the frequency variation of GIC affects the transformer bias and thereby affects the accuracy of the GIC calculation. With the time domain field circuit coupling as the method,a transformer model was built,the dynamic inductance was calculated by the magnetic model,the circuit model was used to work out current,and the dynamic inductance of the transformer and the value waveforms of the exciting current in different frequencies were analyzed so as to identify the bias degree. The results showed if the amplitude of the ESP was constant,and the frequency was from 0. 1Hz to 0. 002Hz,then there would be deviation if GIC was calculated in DC,and the lower the frequency,the less the deviation,if the frequency was below 0. 002Hz,GIC could be calculated in DC,in which the deviation could be ignored.更多还原