A Novel Loss-of-Excitation Protection Scheme based on Load Angle Variation of Parallel Synchronous Generators

Publication Name

Proceedings of 2021 IEEE 2nd International Conference on Smart Technologies for Power, Energy and Control, STPEC 2021


The main weaknesses of the impedance-based loss of excitation (LOE) relay are its mal-operation during the power system disturbances (PSD) and its long detection time during LOE events. In this paper, to rectify the mentioned problems, a new LOE protection scheme is presented based on the load angle (δ) variation of the parallel synchronous generators (SGs) connected to a point of connection (POC). It will be shown that during a PSD, the variation of δ for all parallel SGs is similar such that their δ increases or decreases simultaneously. However, it will be shown that when the LOE happens in one of the parallel SGs, the δ of faulty SG increases while other SGs will experience reduction in their δ. Hence, when more than one SG is connected to a POC, the LOE condition can be discriminated from PSDs by the proposed LOE relay. However, when one SG is connected to the POC, the conventional impedance-based relay is employed to detect LOE/PSD. Since in real condition, the outage rate of the parallel connected SGs in a power plant is very low on a yearly basis, therefore, the contribution of the conventional impedance relay in detection of LOE/PSD is quite limited to some special instances. Simulation studies on a typical power prove high efficiency of the proposed algorithm.

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