Study On New Criterion Of Differential Protection Considering The Saturation Of Current Transformer

TA saturation has always been one of the major reasons to degrade the reliability of the differential protection of transformer. 1) To avoid the mal-operation of transformer differential protection when out-zone fault occurs under current transformer saturation, a simple method of latch-up protection is put forward in this paper. In addition, this principle is also suitable for the slight turn-to-turn inner-fault for the transformer winding. 2) Based on the study about the influence of the distributed capacitance current of UHV transmission line on differential current protection, a principle is put forward in this paper. 3) A new method is put forward in this paper based on the integrated negative vectors. Not only can accurately identify internal fault from external fault, but also protection can be open sensitive for the conversion fault. Lots of simulation results validate its precision and availability.