The probability of faulty synchronization of a generator is very small, but not impossible. The main cause of a faulty synchronization is due to wiring errors caused during maintenance or commissioning when voltage transformer and synchronizing equipment are connected or reconnected wrongly. Faulty synchronizations of synchronous generators cause overcurrent and high electromagnetic torque values that can severely damage, not only the generators their selves, but also prime movers and step-up transformers. Moreover, they produce disturbances on the power system such as power oscillations and voltage sags that can end up collapsing the system if it is not cleared quickly. Despite that, conventional synchronous generator protection systems have not a specific function against faulty synchronizations. This paper presents and analyzes a new and specific protection method against faulty synchronizations. The method is based on an instantaneous low setting overcurrent protection that is only activated during synchronizations. Once the synchronization ends, the protection gets disabled in order to allow the increase of the generator power output. Consequently, it minimizes the damages and the disturbance in the power system through rapid detection and tripping. The method has been successfully validated by computer simulations for a thermal power plant 362 MVA turbo-generator, and by experimental tests on a 5 kVA laboratory generation unit.

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