Patent ID: 7634385

Claim:
A method for measuring expansion efficiency of a turbine within a power plant, said method comprising: operating a Rankine cycle steam power plant including at least one steam turbine at a first load and a first HP throttle steam flow, the steam turbine including a first turbine with superheated exhaust and a second turbine with two phase exhaust and steam extracted to an extraction feedwater heater; determining a first shaft output at the first load with steam extraction flow to the extraction feedwater heater from either a second steam turbine inlet or after partial expansion in the second steam turbine; determining a second shaft output at the first load, the first HP throttle steam flow and the extraction from the second steam turbine to feedwater heating closed; and determining an expansion efficiency of the second steam turbine using the first shaft output, the second shaft output, and a change in extraction steam flow from the second steam turbine.