Steam turbine plant, combined cycle plant provided with same, and method of operating steam turbine plant

A method of operating a steam turbine plant which includes a boiler configured to heat water using a heated fluid to generate steam, and a steam turbine driven using the steam from the boiler, in which the boiler includes one or more evaporators configured to heat water which has flowed therein to a specific heat maximum temperature at constant pressure or more in which a specific heat at constant pressure is maximized using the heated fluid and to convert the water into steam and one or more reheaters configured to heat the steam which has come from the boiler using the heated fluid, and a first steam turbine configured to receive steam supplied from a high-pressure evaporator into which water with the highest pressure flows among the one or more evaporators and a second steam turbine to which the steam which has been heated by the one or more reheaters is supplied are provided as the steam turbine, wherein:

• all the reheaters configured to supply steam to the second steam turbine are disposed only at one side of a downstream side and an upstream side of the high-pressure evaporator in a direction in which the heated fluid flows,
• when all the reheaters are disposed only at the downstream side, all the reheaters heat reheating steam at least containing steam which has passed through the first steam turbine and having a temperature lower than a high-pressure maximum temperature which is the specific heat maximum temperature at constant pressure in the high-pressure evaporator to less than the high-pressure maximum temperature, and
• when all the reheaters are disposed only at the upstream side, all the reheaters heat steam at least containing steam which has passed through the first steam turbine and having a temperature higher than the high-pressure maximum temperature.