基于磁通和电流不对称椭圆模型的变压器励磁涌流判别新算法

依据变压器空投时磁通和电流的严重不对称变化和正常运行或内部故障时磁滞影响使磁通和电流成偏移的近似椭圆对称变化,对磁通和电流做适当的变换处理.在一定数据窗内定义一个反应准椭圆中心的偏移度,并连续取半个周期准椭圆中心的偏移度平均值来反应磁通和电流是否对称变化.变压器空投时偏移度较大;内部故障时偏移度小;空投略微严重的内部故障时偏移度由大到小变化.偏移度大小作为区分励磁涌流和故障电流的判据,简单可靠,具有较高灵敏度.通过试验和仿真证明此种方法可以有效地区分励磁涌流和故障电流,具有较高的实用性.

New algorithm for judging transformer inrush current based on asymmetry elliptical model of flux and current

When the transformer is switched on and energized,the transformer's flux and current will change asymmetrically.When the transformer is under normal or internal windings fault condition,with the influence of hysteresis,the flux and current will approximately correspond to elliptical symmetry change.The flux and current can be transformed properly to the parameters to reflect the symmetry level of the flux and current.A center offset is defined to describe the offset of elliptical center of flux and current in one setting data window.Whether the change of flux and current is symmetric is determined by the half cycle average value of the elliptical center offset.The offset will increase significantly when the transformer is switched on and decrease while the internal winding fault occurs,which makes the offset the criterion to distinguish inrush and fault currents.It can be concluded from the simulation results that offset is a simple,reliable and practical criterion to distinguish inrush and fault currents.