Study On Transformer Microprocessor Protection Based On Positive Sequence Active Power Difference

In order to improve the behavior of transformer protection that is incomplete at present in distinguishing magnetizing inrush current from fault current, the paper puts forward a kind of new principle of transformer differential protection after analyzing the characteristic of magnetizing inrush and active power consume of transformers. This protection uses differential protection based on positive sequence active power as a criterion to discriminate internal faults from magnetizing inrush, and ratio restraint differential current protection as a signal to touch off the protection. The criterion that is based on nonlinear mode of transformers can better reflect the state of transformers that have been proved by academic analysis and EMPT emulation. The paper also gives an instance to realize this protection and explains its software and hardware in details.