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ARTICLES IN THE BOOK

  1. AAAA battery
  2. AAA battery
  3. AA battery
  4. A battery
  5. Absorbent glass mat
  6. Alessandro Volta
  7. Alkaline battery
  8. Alkaline fuel cell
  9. Aluminium battery
  10. Ampere
  11. Atomic battery
  12. Backup battery
  13. Baghdad Battery
  14. Batteries
  15. Battery charger
  16. B battery
  17. Bernard S. Baker
  18. Beta-alumina solid electrolyte
  19. Betavoltaics
  20. Bio-nano generator
  21. Blue energy
  22. Bunsen cell
  23. Car battery
  24. C battery
  25. Clark cell
  26. Concentration cell
  27. Coulomb
  28. 2CR5
  29. Daniell cell
  30. Direct borohydride fuel cell
  31. Direct-ethanol fuel cell
  32. Direct methanol fuel cell
  33. Dry cell
  34. Dry pile
  35. Duracell
  36. Duracell Bunny
  37. Earth battery
  38. Electric charge
  39. Electric current
  40. Electricity
  41. Electrochemical cell
  42. Electrochemical potential
  43. Electro-galvanic fuel cell
  44. Electrolysis
  45. Electrolyte
  46. Electrolytic cell
  47. Electromagnetism
  48. Electromotive force
  49. Energizer Bunny
  50. Energy
  51. Energy density
  52. Energy storage
  53. Flashlight
  54. Float charging
  55. Flow Battery
  56. Formic acid fuel cell
  57. Fuel cell
  58. Fuel cell bus trial
  59. Galvanic cell
  60. Gel battery
  61. Grove cell
  62. Half cell
  63. History of the battery
  64. Hybrid vehicle
  65. Lead-acid battery
  66. Leclanché cell
  67. Lemon battery
  68. List of battery sizes
  69. List of battery types
  70. List of fuel cell vehicles
  71. Lithium battery
  72. Lithium ion batteries
  73. Lithium iron phosphate battery
  74. Lithium polymer cell
  75. LR44 battery
  76. Luigi Galvani
  77. Manganese dioxide
  78. Memory effect
  79. Mercury battery
  80. Metal hydride fuel cell
  81. Methane reformer
  82. Methanol reformer
  83. Michael Faraday
  84. Microbial fuel cell
  85. Molten carbonate fuel cell
  86. Molten salt battery
  87. Nickel-cadmium battery
  88. Nickel-iron battery
  89. Nickel metal hydride
  90. Nickel-zinc battery
  91. Open-circuit voltage
  92. Optoelectric nuclear battery
  93. Organic radical battery
  94. Oxyride battery
  95. Panasonic EV Energy Co
  96. Peukert's law
  97. Phosphoric acid fuel cell
  98. Photoelectrochemical cell
  99. Polymer-based battery
  100. Power density
  101. Power management
  102. Power outage
  103. PP3 battery
  104. Primary cell
  105. Prius
  106. Proton exchange membrane
  107. Proton exchange membrane fuel cell
  108. Protonic ceramic fuel cell
  109. Radioisotope piezoelectric generator
  110. Ragone chart
  111. RCR-V3
  112. Rechargeable alkaline battery
  113. Reverse charging
  114. Reversible fuel cell
  115. Searchlight
  116. Secondary cell
  117. Short circuit
  118. Silver-oxide battery
  119. Smart Battery Data
  120. Smart battery system
  121. Sodium-sulfur battery
  122. Solid oxide fuel cell
  123. Super iron battery
  124. Thermionic converter
  125. Trickle charging
  126. Vanadium redox battery
  127. Volt
  128. Voltage
  129. Voltaic pile
  130. Watch battery
  131. Water-activated battery
  132. Weston cell
  133. Wet cell
  134. Zinc-air battery
  135. Zinc-bromine flow battery
  136. Zinc-carbon battery

 

 
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BATTERIES
This article is from:
http://en.wikipedia.org/wiki/Power_outage

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Power outage

From Wikipedia, the free encyclopedia

 
Tree limbs create a short circuit in electrical lines during a storm that spawned two tornados.
Tree limbs create a short circuit in electrical lines during a storm that spawned two tornados.

A power outage (Also power cut, power failure or power loss) 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 part of the distribution system, a short circuit, or the overloading of electricity mains. While the developed countries enjoy a highly uninterrupted supply of electric power all the time, many developing countries have acute power shortage as compared to the demand. Countries such as Pakistan have several hours of daily power-cuts in almost all cities and villages except the metropolitan cities and the state capitals. Wealthier people in these countries may use a power-inverter or a diesel-run electric generator at their homes during the power-cut.

A power outage may be referred to as a blackout if power is lost completely, or as a brownout if the voltage level is below the normal minimum level specified for the system, or a dropout when the loss of power is only momentary (milliseconds to seconds). Systems supplied with three-phase electric power also suffer brownouts if one or more phases are absent, at reduced voltage, or incorrectly phased. Such malfunctions are particularly damaging to electric motors. Some brownouts, called voltage reductions, are made intentionally to prevent a full power outage. 'Load shedding' or rolling blackout is a common term for a controlled way of rotating available generation capacity between various districts or customers, thus avoiding total wide area blackouts.

Power failures are particularly critical for hospitals, since many life-critical medical devices and tasks require power. For this reason hospitals, just like many enterprises (notably colocation facilities and other datacenters), have emergency power generators which are typically powered by diesel fuel and configured to start automatically, as soon as a power failure occurs. In most third world countries, power cuts go unnoticed by most citizens of upscale means, as maintaining an uninterruptible power supply is often considered an essential facility of a home.

Power outage may also be the cause of sanitary sewer overflow, a condition of discharging raw sewage into the environment. Other life-critical systems such as telecommunications are also required to have emergency power. Telephone exchange rooms usually have arrays of lead-acid batteries for backup and also a socket for connecting a diesel generator during extended periods of outage.

Power outages may also be caused by terrorism (attacking power plants or electricity pylons) in developing countries. The Shining Path movement was the first to copy this tactic from Mao Zedong.

Protecting the power system from outages

In power supply networks, the power generation and the electrical load (demand) must be very close to equal every second to avoid overloading of network components, which can severely damage them. In order to prevent this, parts of the system will automatically disconnect themselves from the rest of the system, or shut themselves down to avoid damage. This is analogous to the role of relays and fuses in households.

Under certain conditions, a network component shutting down can cause current fluctuations in neighboring segments of the network, though this is unlikely, leading to a cascading failure of a larger section of the network. This may range from a building, to a block, to an entire city, to the entire electrical grid.

Modern power systems are designed to be resistant to this sort of cascading failure, but it may be unavoidable (see below). Moreover, since there is no short-term economic benefit to preventing rare large-scale failures, some observers have expressed concern that there is a tendency to erode the resilience of the network over time, which is only corrected after a major failure occurs. It has been claimed that reducing the likelihood of small outages only increases the likelihood of larger ones. In that case, the short-term economic benefit of keeping the individual customer happy increases the likelihood of large-scale blackouts.

Power Analytics

Power Analytics is the term used to describe the management of electrical power distribution, consumption, and preventative maintenance throughout a large organization’s facilities, particularly organizations with high electrical power requirements. For such facilities, electrical power problems – including the worst-case scenario, a full power outage – could have a devastating serious impact. Additionally, it could jeopardize the health and safety of individuals within the facility or in the surrounding community.

Power Analytics use complex mathematical algorithms to detect variations within an organization’s power infrastructure (measurements such as voltage, current, power factor, etc.). Such variations could be early indications of longer-term power problems; when a Power Analytics system detects such variations, it will begin to diagnose the source of the variation, surrounding components, and then the complete electrical power infrastructure. Such systems will – after fully assessing the location and potential magnitude of the problem – predict when and where the potential problem will occur, as well as recommend the preventative maintenance required preempting the problem from occurring.

Restoring power after a wide-area outage

Restoring power after a wide-area outage can be difficult, as power stations need to be brought back on-line. Normally, this is done with the help of power from the rest of the grid. In the absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation.

See also: Uninterruptible power supply

Blackout unavoidabillity and electric sustainability

It has recently been argued on the basis of historical data[1] and computer modelling[2] that power grids are self-organized critical systems. These systems exhibit unavoidable[3] disturbances of all sizes, up to the size of the entire system, and attempts to reduce the probability of small disturbances only increase the probability of large ones[4]. This has immediate policy implications[1]. The following are the relevant quotations from the sources cited:

As expected from studies of general self-organised critical systems, ... apparently sensible efforts to reduce the risk of smaller blackouts can sometimes increase the risk of large blackouts [4]
...the NERC blackout data suggests that the North American power system has been operating near criticality. ...It would be better to analyze this tradeoff between catastrophic blackout risk and loading instead of just waiting for the effects to manifest themselves in the North American power system! [1]
[The models'] PDF of the blackouts size has the same power dependence that have been found from the analysis of NERC data for the North American power grid over a period of 15 years. [2]
First and perhaps most striking is the intrinsic unavoidability of cascading events in such a system when driven near its operational limits. [3]

See also

 
  • List of power outages
  • Renewable energy
  • Rolling blackout
  • Uninterruptible power supply

References

  1. ^ a b c http://www.computer.org/proceedings/hicss/1435/volume2/14350063abs.htm
  2. ^ a b http://ffden-2.phys.uaf.edu/HICSS2002-paper2.pdf
  3. ^ a b http://eceserv0.ece.wisc.edu/~dobson/PAPERS/carrerasHICSS00.pdf
  4. ^ a b http://eetd.lbl.gov/certs/pdf/Dobson_4.pdf

External links

Wikinews has news related to:
Category:Disasters and accidents
  • The Blackout History Project documents two New York City blackouts
  • 3 Major Problems in Restoring Power After a Black Out Space Weather
  • A. E. Motter and Y.-C. Lai, Cascade-based attacks on complex networks, Physical Review E (Rapid Communications) 66, 065102 (2002)
  • Ontario Electricity articles
  • Electricity Power Blackout and Outage tips
  • First-Hand Account of NYC's 2003 Blackout
  • Siemens AG - Blackout Prevention
  • Europe suffers widespread power cuts.
  • How Stuff Works - Blackouts
Retrieved from "http://en.wikipedia.org/wiki/Power_outage"