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.

• 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。