Power system transient stability enhancement by coordinated operation of EVA and SPS

Early valve actuation (EVA) of steam turbine-generator is the method of rapidly reducing the mechanical power output for improving transient stability of a power system. Although the special protection system (SPS) is generally applied for enhancing system stability such as generator tripping, fast turbine valving can be a very effective alternative in case of the aggregated power station. Many turbines in Korea power system have capabilities of fast valving, but they have not tested since installed. This paper first introduces the situations of special protection system installed in Korea. Secondly, the steam flow path and early valve actuation (EVA) scheme are described. Finally, the proposed approach is applied as a countermeasure for enhancing the system stability. And the benefit of EVA is illustrated in time-domain simulations.