Rotor of a modern steam turbine used in a power plant
The turbine generators consist of a series of interconnected steam turbines and a generator on a common shaft. There is one high-pressure turbine at one end, followed by an intermediate pressure turbine, two low-pressure turbines, and a generator. The aim is to move the steam through the system and lose pressure and heat energy expands in mass, requiring increased diameters and longer blades at each stage to successfully extract the remaining energy. The full spin can be over 200 tons and 100 feet (30 m) long. Despite being so heavy it must be kept in slow motion even when closed (3 rpm) so that the shaft won't bow, or even slightly off-center and become unbalanced. This is one of the very important things, it only has five functions of battery power, emergency power failure. Other functions are emergency lighting, communications, station alarms and turbogenerator lubricants.
The superheated steam from the boiler is delivered through 14-16 inch-diameter (360-410 mm) high-pressure turbines, where it has pressures up to 600 psi (4.1 MPa) and 600 ° F (320 ° C) temperature through phases. It escapes through a cold 24-26 inch diameter (610-660 mm) reheat stream and converts back into a specially reheated steam boiler that heats the pendant tube back to 1,000 ° F (500 ° C). Steam heating is carried out to the intermediate pressure turbine where it falls into both temperature and pressure and exits directly to the long low pressure turbine blades and eventually out of the condenser.
The generator, 30 feet (9 m) and 12 feet (3.7 m) wide, contains a stator and a rotating rotor. Operating current generates up to 21,000 amps and 24,000 volts AC (504 MW) as it spins at either 3000 or 3600 rpm, synchronized to the grid. The rotor rotation in a closed chamber cooled with hydrogen gas, is chosen because it has the highest known transfer coefficient of temperature of the gas of any gas and low viscosity reduces wind loss emitted. The system requires special treatment during the start-up, with the air in the first chamber being displaced by carbon dioxide before working with hydrogen. This ensures that no hydrogen-oxygen explosive medium is created.
Grid frequencies across North America are 60 Hz and 50 Hz in Europe, Oceania, Asia (Note: Korea and parts of Japan are the worthy exceptions) and parts of Africa.
The current of a distribution station a transformer increases the voltage to transmit to its destination.
The generator driven steam turbines have auxiliary systems that allow them to work well and safely. Steam turbine generators often have heavy duty, large diameter rotating equipment. Therefore, the required shaft is not only supported and must also be kept in position while running. To minimize the rotation friction, the shaft has a number of bearings. Bearing housing, in which the shaft is rotating, is lined with a low friction material such as Babbitt metal. Lubricating oil is provided to further reduce friction between the shaft and the bearing surface and to limit the heat generated.
