A Novel Differential Protection Scheme for the Generator

This paper presents a new scheme to distinguish the internal fault or the external fault based on phaselet algorithm. For the generator ratio restraint differential protection, the restraint current is decreased owing to CT saturation caused by the external fault, which always results in the maloperation. In order to enhance the operating characteristic of the protection, generator differential protection will select different restraint currents according to the different fault current characteristics. According to that, the method for choosing the corresponding restraint currents is then introduced. The simulation results show that the scheme can effectively prevent the generator differential protection from maloperation caused by CT saturation, and availably enhance the sensitivity of the differential protection during the internal fault.