POWER OUTAGE
A power outage (also called a power cut, a power out, a power failure, a power blackout, a power loss, 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 include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, cascading failure, and 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 usually have backup power sources such as standby generators, which automatically start up when electrical power is lost. Other critical systems, such as telecommunication, must also have emergency power. The battery room of a telephone exchange usually has arrays of lead–acid batteries for backup and a socket for connecting a generator during extended periods of outage. During a power outage, there is a disruption in the supply of electricity, resulting in a loss of power to homes, businesses, and other facilities. Power outages can occur for various reasons, including severe weather conditions (such as storms, hurricanes, or snowstorms), equipment failure, grid overload, or planned maintenance.
Power outages are categorized into three different phenomena relating to the duration and effect of the outage:
A transient fault is a loss of power typically caused by a fault on a power line, e.g. a short circuit or flashover. Power is automatically restored once the fault is cleared.
A brownout is a drop in voltage in an electrical power supply. The term comes from the dimming experienced by incandescent lighting when the voltage sags. Brownouts can cause equipment to perform poorly or even incorrectly operate.
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.
A blackout is the total loss of power to a broader area and long duration. It is the most severe form of power outage that can occur. Blackouts resulting from or in power stations tripping are particularly difficult to recover from quickly.
Rolling blackouts occur when electricity demand exceeds supply, allowing some customers to receive power at the required voltage at the expense of other customers without power. They are common in developing countries and may be scheduled in advance or without warning.
