Comparison Study of Single Valve and Sequential Valve Mode on the Effect of Steam Turbine Heat Rate

Abstract

Net Plant Heat Rate (NPHR) is one of important performance indicator in the generation power plant business which represents efficiency of thermal operation perspective to economic factors. The current mode of turbine valves operation on power plant uses a single valve governor, which results in some thermal losses due to losses during valve operation. Another mode of turbine operation is a sequential mode where one valve governor will sequentially operate toward the full open position as the load demand increases. This sequential mode provides the advantage of reducing potential enthalpy energy losses when throttling the valve governor. Along with the increase in load accompanied by uniform heating of the turbine, when the temperature is stable, the losses that appear practically only come from the pressure losses during the movement. The test results between the 300 and 500 MW load demand show that as the load increases and the temperature of the main steam has stabilized, the turbine heat rate when using sequence mode is more efficient around of 11.9 kcal/kwh than single valve mode. This happens because when conditions are stable that sequential valve can minimize throttling losses (losses that occur when the valve is partially opened), and thus provides the best operating efficiency at partial load.