Comprehensive Countermeasures for Improving the Performance of Transformer Differential Protection

When applied to protecting transformers, the differential protection may mal-operate in the case of magnetizing inrush and current transformer (CT) saturation. Various blocking schemes have been put forward in the past decades, most of which have disadvantages that cannot be ignored. To improve the performance of transformer differential protection, a method to eliminate the magnetizing inrush current is proposed, which can ensure the voltages on both sides have the same phase, but different magnitudes. As for the CT saturation, new methods for identifying the phenomenon are put forward, with which the ability of the differential protection immune to cross-country fault can be improved further. Simulation tests verify the validity of the proposed criterion.