三相涌流波形特征分析及差动保护中采用二次谐波相位制动的原理

The Characteristic Analysis of Three Phase Transformer Inrush and the Discussion of Second Harmonic Restrained Method Using Phase Angle and Amplitude

探讨了GE变压器保护中采用二次谐波附加相位制动原理的适用范围,该原理是从单相变压器涌流特征分析而得到的,但在三相变压器中并不一定完全适用。如对于Y0/?-11接线的变压器,Y0侧空载合闸时由于?绕组中环流助增的影响,引起Y0侧涌流波形的二次谐波幅值、相位特征将不完全同于单相变压器。若保护采用不同的转角方式,其差电流中的二次谐波幅值与相位特征更是不同,论文研究指出基于二次谐波相位的励磁涌流判别方法应充分考虑变压器的接线组别、差动保护的实现原理等的影响。同时研究发现三相分体的变压器各相励磁支路的涌流波形基本上和单相涌流特征相同,如能测量在△侧绕组中的电流并采用两侧绕组电流作为差动臂,那么空载合闸时差动电流就等于励磁支路的电流,同时还能提高区内故障的灵敏度,并且适合采用附加相位制动原理来识别涌流。

The adaptive second harmonic restrained method used in T60 of GE transformer protection device was discussed in this paper. This algorithm was deduced from single transformer but it is not suitable for three winding transformer. When energizing an unload Y0/△- 11 connection transformer on Y0 side, the circulating current in delta side may eliminate or distort inrush current waveforms on Y0 side. This kind of elimination effect phenomenon in inrush current is called the affection of add-assist current （AA） in inrush. It will cause the property of inrush different from single transformer inrush and different compensation method for differential protection also has effect on the amplitude and angle of second harmonic in inrush current. The different connection type for transformer and different compensation method should be considered in differential protection. The further research results show that the characteristic of current in magnetic branch is same as single transformer. The adaptive second harmonic restrained method was suggested if the winding differential protection scheme was used while the CT was mounted on the inner side of A winding. The sensitivity of protection will also be improved by using this scheme.