一种基于差流波形特征的励磁涌流识别方法

提出了一种基于差动电流波形特征的励磁涌流和故障电流识别方法。励磁涌流的共同特征是受铁芯饱和程度的影响,差动电流是流过励磁绕组的实际电流,因而这一特征表现得更加明显。定义波形系数为磁通未饱和部分对应的电流在整个周期中所占比例,当系数大于阈值时判定为励磁涌流。为防止误动,当系数小于阈值时,引入"是否完全偏向时间轴一侧"作为辅助判据,使得该方法更加可靠。最后进行空载合闸仿真试验,证明了该方法能识别各种情况下的励磁涌流,性能优于二次谐波制动和间断角判据。

A method to identify inrush current based on waveform characteristics of differential current

A new method to distinguish inrush current from fault current based on waveform characteristics of differential current is proposed. The common characteristic of inrush currents is that they are all influenced by core saturation. Differential current is the real magnetizing current so that it shows this character more obviously. Waveform coefficient is defined as the percentage of current corresponding to flux unsaturated area in one cycle. If this coefficient is bigger than set value, it would be judged as inrush current. Otherwise an auxiliary criteria of whether waveform is completely located on one side of time axis is introduced to make a further judgment, which makes this method more reliable. The proposed method is verified by digital simulation experiments of no-load closing. The results show that inrush currents in various situations, and the performance of the method is superior to the second harmonic restraint principle and the dead angle principle.