A steam turbine system, including a plurality of blade stages arranged axially along a first shaft, an impulse stage configured upstream of the plurality of blade stages, the impulse stage having an impulse wheel and a casing, the casing including a plurality of inlet sections with each of the plurality of inlet sections having a corresponding nozzle group and operatively connected to a corresponding control valve controlling a first steam flow through the corresponding nozzle group, a first inlet configured to provide the first steam flow through the impulse stage and the plurality of blade stages, and, a second inlet configured to provide a second steam flow to the plurality of blade stages and bypassing the impulse stage.

Provided is a steam turbine in which, among a plurality of stages thereof, a stage that is disposed furthest upstream is a speed-adjusting stage, at least one stage that is disposed downstream of the speed-adjusting stage is a medium-pressure stage, and at least one stage that is disposed downstream of the medium-pressure stage is a low-pressure stage. The speed-adjusting stage is an impulse stage. The medium-pressure stage is a medium reaction degree impulse stage in which the degree of reaction is a medium degree of reaction of 10-40%. The low-pressure stage is a reaction stage having a higher degree of reaction than the medium-pressure stage.

Provided is a steam turbine in which, among a plurality of stages thereof, a stage that is disposed furthest upstream is a speed-adjusting stage, at least one stage that is disposed downstream of the speed-adjusting stage is a medium-pressure stage, and at least one stage that is disposed downstream of the medium-pressure stage is a low-pressure stage. The speed-adjusting stage is an impulse stage. The medium-pressure stage is a medium reaction degree impulse stage in which the degree of reaction is a medium degree of reaction of 10-40%. The low-pressure stage is a reaction stage having a higher degree of reaction than the medium-pressure stage.