基于电子式互感器的变压器励磁涌流识别方法

随着电子式互感器研究的日趋成熟及智能变电站的快速推进，智能变电站已广泛采用电子式互感器获取电流及电压信号。传统的变压器保护采用励磁涌流中的二次谐波含量区分励磁涌流和故障电流，从而对差动保护进行闭锁。但在空投或故障切除后恢复供电时，变压器内部发生轻微匝间故障，受非故障相励磁涌流的影响，差动保护可能延迟动作甚至拒动。针对上述原理的缺陷，提出了二次谐波“或”闭锁原理加故障开放的励磁涌流识别方法。试验结果表明，改进方案能明显提高变压器内部故障时差动保护的动作速度。

Inrush current recognition in power transformer based on electronic transformer

With the maturity of the electronic transformer and advance of the intelligent substation, electronic transformers have been widely used in digital substation for current and voltage signal measurement. Based on the features of inrush current, the traditional transformer differential protection applies its secondary harmonics to distinguish inrush current from fault current to restrain the differential protection. However, if some of transformer faults occur, such as low percentage interturn faults, when a transformer is switched on or the power supply is restored after a fault, the differential protection may delay action even refuse to move. It is because the inrush current of non-fault phase restrained the differential protection. Regarding to the defect in principle, a new unblock criterion of inrush current secondary harmonic is proposed. The results show that the improved scheme can significantly improve the transformer differential protection operation in internal fault.