A Protection for Loss of Field in Synchronous Generator in Presence of Series Compensation Capacitor

In this research, a new approach to safeguard against Loss of Field (LOF) in a synchronous generator, in the presence of a series compensation capacitor, is introduced. LOF can lead to detrimental effects on both the generator and the power network. Impedance-based negative and positive offset MHO relays are employed for the rapid recognition of LOE occurrences in the network. However, issues arise when a series compensation capacitor is integrated into the system, causing maloperation of the protection relays. The introduction of the series compensation capacitor alters the total impedance value, necessitating adjustments to the relay settings for precise functionality. The variation in the overall impedance of the system leads to the underreaching and overreaching of a relay. The study provides detailed explanations and comparisons of both types of MHO relays, along with their respective settings. A simulation is applied in DIGSILENT to assess the effect of series compensation capacitors on offset MHO (negative and positive) relay LOF protection. Ultimately, the article concludes by summarizing the pros and cons of both relay schemes.