A steam-driven turbine system for a power plant in which a high pressure and a low pressure turbine are coupled to a common shaft to drive an external generator. Process steam supply is used as gland sealing steam for the low pressure turbine and turbine driven steam pumps. The high pressure turbine has glands that are self sealing at higher generator outputs, and thus the turbine utilizes the process steam supply for gland sealing only during startup or at low generator outputs. The excess or "spillover" steam that is produced by the high pressure turbine at higher generator outputs is diverted away from the main condenser and/or low pressure feed heater. The spillover steam, which is normally waterlogged, is first passed through a separator to remove excess moisture. The spillover steam is next passed through a superheater to raise its temperature. The spillover steam is then directed to the low pressure turbine and/or turbine driven steam pumps so that it may be used as gland sealing steam. The process steam supply that is replaced by the superheated spillover steam can instead be used to drive the high pressure turbine and increase generator output.