单相变压器空载合闸励磁涌流暂态特性建模与实验

Modeling and experiment investigation of the transient characteristics of magnetizing inrush current in the switch-on of unloaded single phase transformer

变压器在空载合闸时,由于铁芯饱和导致在变压器的一次绕组内会产生很大的励磁涌流。励磁涌流一方面会引起变压器差动保护装置的误动作;另一方面励磁涌流会导致绕组之间产生机械力作用而损伤绕组。通过分析单相变压器空载合闸的数学模型得出了励磁涌流及其间断角的计算公式。采用分流器和数字示波器对不同容量的单相变压器进行测量后得到了与理论分析一致的涌流波形。理论和实验结果表明励磁涌流是含有高次谐波的单侧衰减尖顶波。在相同条件下,合闸角越小、铁芯剩磁越大、饱和磁通越小,都会导致产生更大的励磁涌流幅值。

The primary winding of the transformer will generate large inrush current due to the saturation of iron core when an unloaded transformer is switched-on.The inrush current not only causes mechanical interaction force due to which the windings are damaged,but also induces the differential protection relays to operate incorrectly.In this paper,the mathematical model of unloaded single phase transformer in switch-on is analyzed;the computation formulas of the inrush current and its interruption angle are presented.The experiment investigation of single phase transformers with different capacities shows that the inrush current measurement result is consistent with theoretical analysis.The inrush current waveform is typically a steeple top waveform with high order harmonics and damping in one direction.In the same condition,large inrush current amplitude will be induced with smaller switching angle,larger residual flux and smaller staturation flux.