A Simulation-Based Procedure to Determine Optimum Range of Settings of Fast Valving Action of Steam Turbines to Enhance Frequency Stability

Fast Valving (FV) mechanism of steam turbines is considered to be one of the most effective actions for enhancing the security of a power system subsequent to disturbances. It plays a significant role in mitigating the impact of severe disturbances by instantly decreasing steam turbine power, thus ensuring the power system stability. There is a direct relationship between the settings of Over-Speed Protection Control (OPC) unit of steam turbines and the control functions of FV. This paper proposes a generalized simulation-based procedure to determine the optimum intermediate valve actuation timings of the FV control action. A coal-fired thermal power plant has been used as the case study and the accuracy of the settings made using the proposed approach has been demonstrated using actually happened contingencies in a real power system. Finally, it is concluded that the proper selection of actuation timings of intermediate valves for FV scheme has a significant effect on enhancing frequency stability under transient conditions.