Steam turbine generators have auxiliary systems that allow them to operate satisfactorily and safely. A steam turbine generator, rotating equipment, usually has a large diameter heavy shaft. Therefore, the shaft needs not only supports, but also support during operation. The shaft has a series of bearings to minimize frictional resistance during rotation. The bearings around which the shaft rotates are lined with a low-friction material such as Babbitt metal . Oil lubrication is provided to further reduce friction between the shaft and bearing surface and limit heat generation.
prohibitions
A stall gear (or "tilt gear") is a mechanism designed to rotate the turbogenerator shaft at very low speeds after the unit has been shut down. After the section is "opened" (ie when the steam inlet valve is closed), the turbine descends to a stop. At a complete stop, the turbine shaft tends to warp or warp if left in one position for too long. This is because the heat inside the turbine casing tends to concentrate in the upper half of the casing, with the top of the shaft being hotter than the bottom. Therefore, the shaft can be bent or flexed millions of inches.
This small axis deviation, detected only by the runout indicators, would be enough to cause a vibration that would damage the entire steam turbine after restart. Therefore, the locking gear automatically rotates the shaft at low speed (approximately one percent of rated speed) until it cools enough to stop completely.
Condenser
A surface condenser is a shell and tube heat exchanger in which the cooling water circulates through the tubes. The steam from the low pressure turbine enters the enclosure, where it circulates through the pipes, cools down and turns into condensate (water), as shown in the diagram to the side. These condensers use steam ejectors or motorized rotary extractors to continuously remove air and gas from the steam side to maintain vacuum.For best efficiency, the condenser temperature should be kept as low as possible to achieve the lowest possible condensed vapor pressure. When the vapor pressure is well below atmospheric pressure, the condenser is usually operated under vacuum because the condenser temperature can almost always be kept well below 100°C. Therefore, it is necessary to prevent the leakage of non-condensable air to the closed circuit. Companies operating in hot climates may need to reduce production when the condenser cooling water source heats up; Unfortunately, this often coincides with periods of high electricity demand for air conditioning.
A condenser typically uses recycled cooling water from a cooling tower or water from a river, lake, or ocean to release waste heat into the atmosphere.
food water heater
In the case of a conventional steam power plant using a drum boiler, the surface condenser removes the latent heat of vaporization from the steam as it changes from steam to liquid. The amount of heat (Joules or Btu ) in a vapor is called enthalpy. The condensate pump then pumps the condensate through the feedwater heater. The feedwater heating equipment then raises the temperature of the water using the steam generated by the various stages of the turbine.Feedwater preheating reduces the irreversibility associated with steam generation and thus increases the thermodynamic efficiency of the system. This reduces plant operating costs and also helps prevent thermal shock to the boiler metal when the feedwater returns to the steam cycle.
great heater
When the steam is conditioned by the drying equipment inside the drum, it moves from the upper area of the drum to the pipes laid in the different areas of the boiler. The so-called heating and heating zones. The steam acquires energy and its temperature is superheated above the saturation temperature. The superheated steam is then directed through main steam lines to high pressure turbine valves.
deaerator
A steam-generating boiler requires that the boiler feedwater be free of air and other dissolved gases, especially corrosive gases, to prevent metal corrosion.Power plants typically use a deaerator to remove air and other dissolved gases from boiler water. A deaerator typically consists of a vertical domed vent unit mounted above a horizontal cylindrical tank that acts as a degassed boiler feedwater reservoir.
There are many different models of deaerators and designs vary from manufacturer to manufacturer. The diagram to the right shows a typical conventional clean deaerator. When used correctly, most deaerator manufacturers guarantee that degassed water will contain no more than 7 parts per billion (0.005 cm³/L) of oxygen by weight.
Auxiliary systems
oil system
An auxiliary oil system pump is used to supply oil during startup of the steam turbine generator. Provides the necessary hydraulic oil system for the steam turbine main inlet steam shutoff valve, control valves, bearing and seal oil systems, associated hydraulic relays, and other mechanisms.
During startups, at a given turbine speed, the functions of the auxiliary system are taken over by the pump, which is driven by the main turbine shaft.
Generator heat output
An electrical generator requires cooling to dissipate the heat it generates. While smaller units can be cooled with air drawn from intake filters, larger units generally require special cooling units. Hydrogen gas cooling is used in an oil pan because it has the highest known heat transfer coefficient of any gas and its low viscosity, which reduces losses to air. This system requires special treatment during start-up, the air in the chamber is first replaced by carbon dioxide before being filled with hydrogen. This ensures that flammable hydrogen does not mix with oxygen in the air.
The hydrogen pressure inside the enclosure is kept just above the atmosphere to prevent the entry of outside air. When the hydrogen well leaves the crankcase, it must be sealed against leakage to the outside. The mechanical seals around the shaft are installed with a very small clearance to prevent friction between the shaft and the seals. Seal oil is used to prevent hydrogen from escaping into the atmosphere.
The generator also uses water cooling. Since the generator windings are rated around 22 kV and are permeable to water, an insulating barrier such as Teflon is used to connect the water line and high voltage generator windings. Low permeability demineralized water is used.
High voltage generator system
Generator voltage ranges from 11 kV on small units to 22 kV on large units. High voltage generator cables are usually large aluminum tubes due to higher currents than cables used in small machines. They are connected to well grounded aluminum bars and are supported by suitable insulators. The high voltage generator channels are connected to step-up transformers for connection to a high voltage substation (115-520 kV) for further transmission to the local power grid.
The necessary protection and metering devices for high voltage wiring are included. Thus, the steam turbine and the transformer form a single entity. The smaller units generating 11 kV are equipped with a switch for connection to the 11 kV common bus system.