变压器差动保护中电流相位补偿方式的分析

在变压器空载合闸时，对变压器差动保护中△→Y电流相位补偿方式进行分析，证明变换后得到的某相差流并不能反映该相励磁电流的真实变化。进一步利用MATLAB仿真YN，d11变压器空载合闸，对比分析了变压器差动保护中△→Y和Y→△这2种电流相位补偿方式对二次谐波比励磁涌流闭锁判据的影响，仿真结果表明前者并不比后者具有明显的优势，也不宜采用分相闭锁差动保护。同时，分析变压器对称涌流产生的原因，计算说明对称涌流中的二次谐波比并不一定比单侧涌流低。提出了利用未经补偿的相电流计算励磁涌流闭锁判据中二次谐波比，提高分相闭锁的可靠性，以及利用综合二次谐波比全相闭锁保护、加短延时投入分相开放判据开放保护，提高带故障合闸时保护动作速度的思想。

Analysis on the Current Phase Compensation Methods in Differential Protection for Transformer

By analyzing the current phase compensation method from delta to star connection, it is showed that the compensated differential current cannot reflect the characteristics of magnetizing current, when a transformer is energized. Furthermore, using the Matlab power system toolbox to simulate the magnetizing inrush current when a transformer YN, d11 switching on without load, the effects of two kinds of current phase compensation methods, from delta to star and from star to delta connection, on the ratio of second harmonic based scheme against the inrush current are compared. The calculation results show that the former has no advantage over the later on distinguishing the inrush, and split-phase blocking the differential should not be adopted for all of them. The cause of symmetric inrush is analyzed, and the simulation results show that the ratio of second harmonic in the symmetric inrush is not lower than that in the asymmetric inrush. Based on the comparison, the reliability of blocking scheme is improved by using the phase current without compensation to calculate the ratio of second harmonic. Furthermore it is proposed that using the comprehensive ratio of second harmonic to block the differential protection in all-phase and the open scheme to open the protection after a time delay can improve the operation speed of protection when the transformer is switched on with a short-circuit fault.