Emergency power system
Emergency power systems are a type of system, which may include lighting, generators and other apparatus, to provide backup resources in a crisis or when regular systems fail. They find uses in a wide variety of settings from residential homes to
hospitals, scientific laboratories and modern naval ships. Emergency power systems can rely on generators, deep cycle batteries, Flywheel energy storageor hydrogen fuel cells [ [http://www1.eere.energy.gov/femp/pdfs/hydrogenfc_tir.pdf Fuel Cells in Backup Power Applications] ] [ [http://www1.eere.energy.gov/hydrogenandfuelcells/education/pdfs/early_markets_backup_power.pdf DOE Fuel Cells for Backup Power] ] . Finally, some homebrew emergency power systems use regular lead-acid car batteries, but these do not make a very efficient or reliable system. [cite web|url=http://home.howstuffworks.com/emergency-power1.htm |title=Lead-acid car batteries also used in homebrew emergency power systems]
Emergency power systems were used as early as
World War IIon naval ships. In combat, a ship may lose the function of its steam engines, which power the steam driven turbines for the generator. In such a case, one or more diesel engine(s) are used to drive back-up generators. Early transfer switches relied on manual operation; two switches would be placed horizontally, in line and the "on" position facing each other. a rod is placed in between. In order to operate the switch one source must be turned off, the rod moved to the other side and the other source turned on.
Operation in buildings
Utility power (known as normal power) can be lost due to downed lines, malfunctions at a sub-station, planned blackouts or in extreme cases a grid-wide failure. In modern buildings, most emergency power systems have been and are still based around on generators. Usually, these generators are
diesel enginedriven, although smaller buildings may use a gasoline enginedriven generator and larger ones a gas turbine. However, lately, more use is being made of deep cycle batteries and other technologies such as flywheel energy storageor fuel cells. These latter systems do not produce polluting gases, thereby allowing the placement to be done within the building. Also, as a second advantage, they do not require a separate shed to be built for fuel storage. [cite web|url=http://home.howstuffworks.com/emergency-power3.htm|title=Advantages of deep-cycle batteries over generators] .
With regular generators, an automatic
transfer switchis used to connect emergency power. One side is connected to both the normal power feed and the emergency power feed; and the other side is connected to the load designated as emergency. If no electricity comes in on the normal side, the transfer switch uses a solenoid to throw a triple pole, single throw switch. This switches the feed from normal to emergency power. The loss of normal power also triggers a battery operated starter system to start the generator, similar to using a car battery to start an engine. Once the transfer switch is switched and the generator starts, the building's emergency power comes back on (after going off when normal power was lost.)
emergency lights, emergency lighting is not a type of light fixture; it is a pattern of the building's normal lights that provides a path of lights to allow for safe exit, or lights up service areas such as mechanical rooms and electric rooms. Fire alarm systems and the electric motor pumps for the fire sprinklers is almost always on emergency power. Other equipment on emergency power may include smoke isolation dampers, smoke evacuation fans, handicap doors and outlets in service areas. Hospitals use emergency power outlets to power life supportsystems and monitoring equipment. Some buildings may even use emergency power as part of normal operations, such as a theater using it to power show equipment because "the show must go on".
Electronic device protection
Computers, communication networks and other modern electronic devices need not only power, but also a steady flow of it to continue to operate. If the source voltage drops significantly or drops out completely these devices will fail, even if it is for a fraction of a second. Because of this, even a generator back-up does not provide protection because of the start-up time involved.
To achieve this, extra equipment such as surge protectors, inverters, or a sometimes a complete
uninterruptible power supply(UPS) is used. UPS systems can be local or building wide. A local UPS is a small box that fits under a desk or a telecom rack and powers a small number of devices. A building wide UPS can take on several different forms, depending on the application. It directly feeds a system of outlets designated as UPS feed and can power a large number of devices.
telephone exchanges use DC, the building's battery room is generally wired directly to the consuming equipment and floats continuously on the output of the rectifiers that normally supply DC rectified from utility power. When utility power fails, the battery carries the load without needing to switch. With this simple though somewhat expensive system, some exchanges have never lost power for a moment since the 1920s.
tructure and operation in utility stations
In recent years, large units of a utility power station are usually designed on a unit system basis in which the required devices, including the boiler, the turbine generator unit, and its power (step up) and unit (auxiliary)
transformerare solidly connected as one unit. A less common set-up consists of two units grouped together with one common station auxiliary. As each turbine generator unit has its own attached unit auxiliary transformer, it is connected to the circuit automatically. For starting the unit, the auxiliaries are supplied with power by another unit (auxiliary) transformer or station auxiliary transformer. The period of switching from the first unit transformer to the next unit is designed for automatic, instantaneous operation in times when the emergency power system needs to kick in. It is imperative that the power to unit auxiliaries not fail during a station shutdown (an occurrence known as black-out when all regular units temporarily fail). Instead, during shutdowns the grid is expected to remain operational. When problems occur, it is usually due to reverse power relays and frequency-operated relays on grid lines due to severe grid disturbances. Under these circumstances, the emergency station supply must kick in to avoid damage to any equipment and to prevent hazardous situations such as the release of hydrogengas from generators to the local environment.
In nuclear power plants
Emergency power systems, called there Emergency Diesel Generators (EDGs), are a required feature in nuclear power plants. They are typically installed in sets of three. The EDG installation is designed to the same safety-grade requirements as the other safety systems in the plant. The next (upcoming) generation of nuclear power plants includes some designs with multiple independent banks of EDGs (as in the
ABWRs [ [http://www.nuc.berkeley.edu/designs/abwr/safe.html Simplified Active Safety Systems [for the ABWR]] ] ).
Controlling the emergency power system
For a 208 VAC emergency supply system, a central battery system with automatic controls, located in the power station building itself, is used to avoid long electric supply wires. This central battery system consists of
lead-acid batterycell units to make up a 12 or 24 VDC system as well as stand-by cells, each with its own battery charging unit. Also needed are a voltage sensing unit capable of receiving 208 VAC and an automatic system that is able to signal to and activate the emergency supply circuit in case of failure of 208 VAC station supply.
* [http://www.howstuffworks.com/emergency-power.htm How Emergency Power Systems Work]
* [http://www.popularmechanics.com/how_to_central/home_clinic/1275631.html?page=1 How to Install a backup generator]
* [http://www.howstuffworks.com/question219.htm Difference between car battery and deep-cycle batteries]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Emergency Alert System — The Emergency Alert System (EAS) is a national warning system in the U.S. put into place in 1994, superseding the Emergency Broadcast System (EBS) and the CONELRAD System and is jointly coordinated by the Federal Communications Commission (FCC),… … Wikipedia
Power system — refers to Electric power transmissionee also*Continual power system *Emergency power system *Power Systems CAD … Wikipedia
Emergency warning system for vehicles — Telematics technologies are self orientating open network architecture structure of variable programmable intelligent beacons developed for application in the development of intelligent vehicles with target intent to accord (blend, or mesh)… … Wikipedia
Continual power system — A continual power system is a large scale system for reliably supplying large amounts of uninterrupted power. It has some features of an uninterruptible power supply and others of an emergency power system. An example of a continual power system… … Wikipedia
War emergency power — (WEP) is an American term for the throttle setting on some World War II military aircraft engines. For use in emergency situations, it produced more than 100% of the engine s normal rated power for a limited amount of time, often about five… … Wikipedia
Emergency management — Accident preparedness redirects here. For Safety related articles, see Safety. Disaster preparedness redirects here. For other articles related to disaster preparedness, see Category:Disaster preparedness. Emergency management is the generic name … Wikipedia
Power outage — A power outage (also known as power cut , power failure , power loss , or blackout ) is the loss of the electricity supply to an area.The reasons for a power failure can for instance be a defect in a power station, damage to a power line or other … Wikipedia
Emergency telephone number — Many countries public telephone networks have a single emergency telephone number, sometimes known as the universal emergency telephone number or occasionally the emergency services number, that allows a caller to contact local emergency services … Wikipedia
Power station — A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of electric power. [cite book|author=British Electricity International|title=Modern Power Station Practice:… … Wikipedia
Emergency Rule — (OHAL) Since the inception of the Republic of Turkey in 1923 until recently, for most of the time the Kurdish provinces in the southeast have been ruled by various special regimes, such as martial law, state of siege, and, from the summer of… … Historical Dictionary of the Kurds