Protection scheme enhancement of synchronous generator

Abstract

Synchronous generator is the most important element of a power system and its fast and reliable protection is crucial. One of the most abnormal conditions in a generator is loss of excitation (LOE) which is harmful to both the generator and the power system. This condition should be detected and the generator isolated from the system to avoid generator damage as well as power system instability. This thesis presents a study and comparison of the two conventional LOE protection schemes, negative-offset and positive-offset mho element under different conditions. The results show that the two schemes can detect LOE fault under total or partial LOE conditions, however in terms of speed (fault detection time) the positive offset scheme is faster than the negative offset scheme under all loading conditions. Besides, the two LOE protection schemes are reliable and do not operate under power swing disturbances caused by any type of external faults. Moreover, the impact of the static synchronous compensator (STATCOM) on the positive-offset mho element LOE protection scheme is investigated. The obtained results show that the operation of the positive-offset protection scheme takes more time under the integration of STATCOM in the transmission line. Finally, to reduce this delay time, an enhanced method based on phasor measurement unit (PMU) is proposed. The simulation results show that the new developed method improves the operation of the positive offset mho element LOE protection by reducing the delay time that may be due to the presence of STATCOM