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.
A power outage may be referred to as a blackout if power is lost completely, or as a brownout if some power supply is retained, but the voltage level is below the minimum level specified for the system.
Power failures are particularly damaging for hospitals, since many life-critical medical devices and tasks require power. For this reason hospitals, just like many enterprises, have emergency power generators which are typically powered by Diesel fuel and configured to start automatically, as soon as a power failure occurs.
Other life-critical systems such as telecommunications are also required to have emergency power.
| Table of contents |
|
2 Restoring power after a wide-area outage 3 Blackouts are unavoidable? and electric sustainability 4 See also 5 External links |
In power supply networks, the power generation and the demand must be closely matched 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 network.
Modern power systems are meant to be 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 of 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 increses the likelihood of large-scale blackouts.
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:
It has recently been argued on the basis of historical data 2002a and computer modelling 2002b that power grids are self-organized critical systems. These systems exhibit unavoidable 2000 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 2003. This has immediate policy implications 2002a. The following are the relevant quotations from the sources cited:
Protecting the power system from outages
Restoring power after a wide-area outage
Blackouts are unavoidable? and electric sustainability
See also
External links