Loss of field (LOF) phenomenon in synchronous generators may cause serious damages and voltage drop in power system, which can be terminated to an unintended blackout. Conventional methods detect LOF on the basis of the measured impedance from viewpoint of the related terminals. Such methods not only are not fast enough, but also may exhibit mal-operation in the face of other phenomena, e.g. stable power swing (SPS).

In this paper, a novel algorithm is proposed to detect LOF in synchronous generators on the basis of some electrical parameters variations, including voltage (V), current (I), active power (P), reactive power (Q) and power angle (&delta). To evaluate the proposed method performance, some cases are simulated on a sample multi-machine power system under various operation conditions. Obtained results show that the proposed algorithm on the basis of V, Q and &delta not only can be considered as a fast LOF detector in comparison with the conventional impedance-based schemes, but also it can be introduced as a robust and secure technique in the face of SPS and other power system disturbances.