变压器采样值差动保护误动分析及改进

Analysis and Improvement on Malfunction of Sampled Value Differential Protection for Transformer

结合一次220kV主变空投时采样值差动保护误动的案例,对变压器采样值差动保护误动的原因进行了详细分析,提出了一种新的改进方法。通过对现场录波数据进行分析,发现励磁涌流间断角消失是导致采样值差动保护误动的主要原因。新方法一方面通过对差动电流进行差分算法,可以部分恢复间断角,消除了CT饱和引起的反向电流的影响;另一方面,通过对采样值差动启动定值进行合理的选取,在不降低灵敏度的前提下,可以有效防止误动。大量的动模试验和现场应用表明,该改进方法能有效提高采样值差动保护抗励磁涌流的能力。

Based on the case of typical malfunction of sampled value differential protection when no load 220kV transformer is put into power grid,the cause of malfunction is analyzed in detail,and a kind of new improved method is proposed.Through the analysis of recording data,the disappearance of intermission angle of magnetizing inrush current is the main cause of malfunction of sampled value differential protection.Through differential current improved by using of differential algorithm,the intermission angle can be recovered partly by proposed approach,which eliminates the affection of reverse current caused by CT saturation.In addition,through proper selecting of start-up set value of sampled value differential protection,the malfunction can be effectively avoided with same sensitivity.The experiments and applications show that proposed method can effectively improve the ability of anti-excitation current for sampled value differential protection.