基于FFT的变压器励磁涌流谐波含量计算方法

The calculation method of harmonic content of transformer inrush current based on FFT

变压器空载合闸或外部故障切除电压恢复的过程中,会产生幅值可达额定电流十数倍的励磁涌流。该涌流只经过变压器电源侧,必然流入主变差流回路,可能导致纵联差动保护误动。以湖南电网220 kV新一代智能变电站主变压器的实际参数进行研究,在Matlab/Simulink中建立励磁涌流仿真模型,对不同合闸初相角条件下变压器各相的涌流特性进行了仿真计算。利用快速傅里叶算法(Fast Fourier Transformation,FFT)对涌流电流的谐波含量进行计算。在此基础上对励磁涌流的产生机理、间断角等内容进行了研究和分析。研究结果表明,所述方法可对实际工程保护定值的合理性进行验证。

The inrush current that is several or even a dozen times of rated current can appear when the transformer closing switch without loads. This current only flows through one side of transformer. So, it drains into the current dif- ferential loop and may lead to the false action of protection. The simulation models are set up by means of the Matlab/ Simulink software according to the actual parameters of main transformer in 220 kV new generation smart substation of Hunan power grid. The inrush current model under different closing initial angles is simulated and calculated. The fast Fourier transformation algorithm （FFT） is used to calculate the harmonic content of inrush current, meanwhile, the generating mechanism, and discontinuous angles are also researched and analyzed. The rationality of protection setting value can be verified with this method according to the research results.