User Tools

Site Tools


power_outage

Power outages are a loss of functionality electrical distribution grid, they can be very wide spread or very local. A Rolling Blackout is an intentional shedding of load by a power utility due to insufficient power generation or inadequate power transmission capability. Regardless of the cause, a blackout can affect the population adversely.

Blackout.jpg

Effects

Blackouts are an often over-looked but potentially very serious disaster, depending upon one's location and stored provisions. Blackouts are most severe in heavily populated, apartment dense areas that rely on refrigeration for food storage. When the power goes out the food spoils quickly, the windows on high-rise apartments won't open for ventilation, and apartment dwellers can't easily exit their buildings. People become stranded in elevators, and travel can be constrained due to the traffic control and mass-transit systems going down. There can even be a breakdown in law and order due to a widespread urban blackout.

Examples

The most famous case of a blackout turning into civil unrest is the New York City Blackout of July 13-14, 1977. Combined with widespread hysteria regarding the “Son of Sam” serial murders and a brutal heat wave, the city suffered widespread looting, property crimes and arson. Rioting continued during daylight hours despite police presence, and there were 31 neighborhoods that suffered looting and vandalism. There were over 4,500 looters arrested during the two days and 3,776 people were arrested for other charges while the NYPD suffered 550 casualties. A total of 1,616 stores were damaged and 1,037 fires were set for an estimated total damages of over $300 million.

Preparation & Mitigation

Preparation for a blackout begins by looking at your home to determine what are your critical systems that require power. For instance, it may be your furnace or electric baseboard heaters, air conditioning unit, water pump, or your refrigerator/freezer. Next, look at what systems or devices would suffer if a power spike (surge), power drop (brownout), or outage (blackout) occurred without warning. That may be your computer, home entertainment system, or home security system. Then, prepare to mitigate the damage and power loss by taking some or all of the following steps:

  • Adding Surge Protectors to non-critical but expensive systems, such as entertainment centers, TV's, DVR's, etc.
  • Adding Uninterruptable Power Supplies (UPS) with battery backups for critical systems that need time to properly shut down, such as PC's and laptops.
  • Replacing electrical appliances such as refrigerators, freezers, stoves and water heaters with alternatives such as natural gas, propane (LP), or kerosene powered appliances.
  • Have a telephone line that can be used without power, for example, a corded phone without an answering machine.
  • Have enough flashlights, candles, radios and batteries for the entire family.
  • Adding an emergency generator with fuel storage.
  • Going completely “off the grid” and becoming self-sufficient through an alternative power system.

Historic Blackouts

See Also

References

Man-made Disaster

Snippet from Wikipedia: Power outage

A power outage (also called a power cut, a power out, a power blackout, power failure or a blackout) is the loss of the electrical power network supply to an end user.

There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, cascading failure, fuse or circuit breaker operation.

Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as hospitals, sewage treatment plants and mines, will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other critical systems, such as telecommunication, are also required to have emergency power. The battery room of a telephone exchange usually has arrays of lead–acid batteries for backup and also a socket for connecting a generator during extended periods of outage.

File:PowerOutageBlackout.svgFile:PowerOutageDropout.svg

A power outage (also power cut, blackout, or power failure) is a short- or long-term loss of the electric power to an area.

There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, or the overloading of electricity mains.

Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as hospitals, sewage treatment plants, mines, and the like will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other 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 generator during extended periods of outage.

Types of power outage

Power outages are categorized into three different phenomena, relating to the duration and effect of the outage:

  • A transient fault is a momentary (a few seconds) loss of power typically caused by a temporary fault on a power line. Power is automatically restored once the fault is cleared.
  • A brownout or sag is a drop in voltage in an electrical power supply. The term brownout comes from the dimming experienced by lighting when the voltage sags. Brownouts can cause poor performance of equipment or even incorrect operation.
  • A blackout refers to the total loss of power to an area and is the most severe form of power outage that can occur. Blackouts which result from or result in power stations tripping are particularly difficult to recover from quickly. Outages may last from a few minutes to a few weeks depending on the nature of the blackout and the configuration of the electrical network.

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. Protective relays and fuses are used to automatically detect overloads and to disconnect circuits at risk of damage.

Under certain conditions, a network component shutting down can cause current fluctuations in neighboring segments of the network 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 an 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.

Protecting computer systems from power outages

Computer systems and other electronic devices containing logic circuitry are susceptible to data loss or hardware damage that can be caused by the sudden loss of power. These can include data networking equipment, video projectors, alarm systems as well as computers. To protect against this, the use of an uninterruptible power supply or UPS can provide a constant flow of electricity if a primary power supply becomes unavailable for a short period of time. To protect against surges (events where voltages increase for a few seconds), which can damage hardware when power is restored, a special device called a surge protector that absorbs the excess voltage can be used.

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 total absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation. The means of doing so will depend greatly on local circumstances and operational policies, but typically transmission utilities will establish localized 'power islands' which are then progressively coupled together. To maintain supply frequencies within tolerable limits during this process, demand must be reconnected at the same pace that generation is restored, requiring close coordination between power stations, transmission and distribution organizations.

Blackout inevitability and electric sustainability

Self-organized criticality

It has been argued on the basis of historical data<ref name=“ref2002a”>IEEE Computer Society Conference Publishing Services<!-- Bot generated title --></ref> and computer modeling<ref name=“ref2002b”>Microsoft Word – HICSS2002-paper2<!-- Bot generated title --></ref> that power grids are self-organized critical systems. These systems exhibit unavoidable<ref name=“ref2000”>http://eceserv0.ece.wisc.edu/~dobson/PAPERS/carrerasHICSS00.pdf</ref> disturbances of all sizes, up to the size of the entire system. This phenomenon has been attributed to steadily increasing demand/load, the economics of running a power company, and the limits of modern engineering.<ref name=“ref2007”>Dobson et al. Complex systems analysis of series of blackouts: Cascading failure, critical points, and self-organization. Chaos 17, 2007.</ref> While blackout frequency has been shown to be reduced by operating it further from its critical point, it generally isn’t economically feasible, causing providers to increase the average load over time or upgrade less often resulting in the grid moving itself closer to its critical point. Conversely, a system past the critical point will experience too many blackouts leading to system-wide upgrades moving it back below the critical point. The term critical point of the system is used here in the sense of statistical physics and nonlinear dynamics, representing the point where a system undergoes a phase transition; in this case the transition from a steady reliable grid with few cascading failures to a very sporadic unreliable grid with common cascading failures. Near the critical point the relationship between blackout frequency and size follows a power law distribution.<ref name=“ref2007”/> Other leaders are dismissive of system theories that conclude that blackouts are inevitable, but do agree that the basic operation of the grid must be changed. The Electric Power Research Institute champions the use of smart grid features such as power control devices employing advanced sensors to coordinate the grid. Others advocate greater use of electronically controlled High-voltage direct current (HVDC) firebreaks to prevent disturbances from cascading across AC lines in a wide area grid.<ref>

</ref>

Cascading failure becomes much more common close to this critical point. The power law relationship is seen in both historical data and model systems.<ref name=“ref2007”/> The practice of operating these systems much closer to their maximum capacity leads to magnified effects of random, unavoidable disturbances due to aging, weather, human interaction etc. While near the critical point, these failures have a greater effect on the surrounding components due to individual components carrying a larger load. This results in the larger load from the failing component having to be redistributed in larger quantities across the system, making it more likely for additional components not directly affected by the disturbance to fail, igniting costly and dangerous cascading failures.<ref name=“ref2007”/> These initial disturbances causing blackouts are all the more unexpected and unavoidable due to actions of the power suppliers to prevent obvious disturbances (cutting back trees, separating lines in windy areas, replacing aging components etc.). The complexity of most power grids often makes the initial cause of a blackout extremely hard to identify.

Mitigation of power outage frequency

The effects of trying to mitigate cascading failures near the critical point in an economically feasible fashion are often shown to not be beneficial and often even detrimental. Four mitigation methods have been tested using the OPA blackout model:<ref name=“ref2003”>Dobson et al. Blackout Mitigation Assessment in Power Transmission Systems. System Sciences 2003.</ref>

  • Increase critical number of failures causing cascading blackouts – Shown to decrease the frequency of smaller blackouts but increase that of larger blackouts.
  • Increase individual power line max load – Shown to increase the frequency of smaller blackouts and decrease that of larger blackouts.
  • Combination of increasing critical number and max load of lines – Shown to have no significant effect on either size of blackout. The resulting minor reduction in the frequency of blackouts is projected to not be worth the cost of the implementation.
  • Increase the excess power available to the grid – Shown to decrease the frequency of smaller blackouts but increase that of larger blackouts.

In addition to the finding of each mitigation strategy having a cost-benefit relationship with regards to frequency of small and large blackouts, the total number of blackout events was not significantly reduced by any of the above mentioned mitigation measures.<ref name=“ref2003”/>

A complex network-based model to control large cascading failures (blackouts) using local information only was proposed by A. E. Motter.<ref>Cascade control and defense in complex networks, Phys. Rev. Lett. 93, 098701 (2004).</ref>

Key performance Indicators

Utilities are measured on three specific performance measures:

See also

References

External links

power_outage.txt · Last modified: 2020/03/12 18:37 (external edit)