主设备变压器保护谐波制动改进

传统的变压器保护采用励磁涌流中二次谐波的含量区分是励磁涌流还是故障电流，从而对差动继电器进行闭锁，但在空投或故障切除后恢复供电时，变压器发生某些故障，如轻微匝间故障，励磁涌流与故障电流叠加，由于变压器容量，电压等级，变压器的铁芯结构等因素影响，励磁涌流可能长达5s才能衰减，此时可能造成变压器保护的实际拒动，针对上述原理的缺陷，提出二次谐波的涌流加速原理，充分利用CPU的快速处理能力，使变压器在发生上述故障时快速动作，提高保护的动作时间。

Advancement of central equipment transformer protection's harmonic restraint

Based on the features of inrush current, the traditional transformer differential protection applies its 2 nd harmonic to distinguish inrush current from fault current to restrain the relay trip. However, if some of transformer faults occur, such as slight inter-turn S/C, when a transformer is switched on or the power supply is restored after a fault, the protection failure may happen. It is because the inrush current and fault current are cumulated and decayed in 5 seconds, which is influenced by the transformer capacity, voltage rating and core structure. Regarding to the defect in principle, an acceleration principle of inrush current 2 nd harmonic is proposed, which takes full use of the processing ability of CPU and speeds up the response time during the conditions mentioned above.