Half Cycle Negative Sequence Differential Protection for Synchronous Generator

In this paper, a half cycle negative-sequence differential protection principle for internal faults in synchronous generators is presented. In the presented scheme, a new modified half-cycle discrete Fourier transform (DFT)-based phasor estimation algorithm is used. This scheme has many advantages over conventional differential protection (87P) in terms of sensitivity, speed, security, and reliability. The presented technique has been verified on a Phase Domain Synchronous Machine model simulated on the Real Time Digital Simulator (RTDS®). The analysis of congregated fault dataset clearly shows that the scheme is able to discriminate well between internal and external faults even during current transformer saturation, unbalance condition and overloading.