Steam Turbine

Overview

A steam turbine extracts work from high-pressure, high-temperature steam and converts it into rotating shaft power to drive a generator. This 250 MW condensing unit forms the heart of a thermal power plant, taking steam from a boiler at 170 bar and 538 °C and exhausting into a vacuum condenser to maximise the energy recovered. Steam expands through successive stages, dropping in pressure and temperature while the rotor accelerates the flow against fixed nozzles and reaction blades.

Construction

Steam enters through the Steam Admission section, where stop and control valves regulate flow into the machine. It then expands across the Stationary Flow Path diaphragm and nozzle stages, which direct and accelerate the steam onto the moving blades. The Turbine Rotor carries those blades; as steam passes over them it imparts torque, spinning the rotor at a constant 3000 RPM.

Pressure containment and stage separation are provided by the Turbine Casing, the HP and LP casing assembly that holds the stationary parts and confines the expanding steam. The rotor turns within the Bearing Assembly, journal bearings carrying its weight and a thrust bearing absorbing axial steam force, all fed by the Lube Oil System system.

Mechanical output passes through the Coupling & Reduction Gear to the Generator, a 3000 RPM synchronous machine producing 15.75 kV. Exhaust steam leaves through the Condenser Interface hood into the condenser, where it is cooled back to water and the vacuum is maintained.

Speed and load are held by the Governing & Control System electrohydraulic control, which throttles the admission valves. When offline, the Turning Gear slowly rotates the rotor to prevent thermal bowing, and the whole machine is aligned on the Foundation & Baseplate baseplate.