Improvements to generator differential protection based on the criterion of signs of the DC-component

Generator differential protection is one of the most important electrical protections of synchronous generator. Its operation principle is based on the comparison of the input current and output current at each phase winding and it allows the trip when the currents are not similar. In many cases, a false differential current causes unwanted trip commands as a result of the saturation of current transformers (CTs). In this paper, the proposed criterion can identify whether it is an external fault or an internal fault in the protection zone and it allows preventing trip commands which have been caused by the saturation of the CTs.