ABSTRACT
The world's largest single-shaft generator is rated at 1750 MW output. The microgrid and distributive power generators are small, which are of the order of 100 kW or even less. Device 51V is for the generator backup protection to disconnect the generator from the system if a system fault has not been cleared by other protective devices after a sufficient time delay has elapsed. It protects the system components against excessive damage and prevents generator and its auxiliaries from exceeding their thermal limitations. The presence of power system harmonics can overload the generators with respect to negative-sequence currents. The source of excitation to a generator can be completely or partially removed due to accidental tripping of the field breaker, field short circuit, or loss of supply to the excitation system. This presents a serious operating condition to the operation of the generator. The primary protection is provided by automatic load shedding programs in the power system.
