A black start is a capability of select power stations, which allows a given station to generate its own power to enable it to restart after a power failure. The main purpose of black starts is to allow fast restoration of power to the grid when a power failure, or black out, occurs. Most power stations cannot restart without off-station power after a power failure, so the ability of some stations to perform black starts is imperative to achieve efficient reestablishment of power after a black out. Once these stations have completed their black starts, they can be connected to the rest of the power network and assist in restoring non-black start stations to power.
Accomplished by a complex process using small electrical generators, black starts reestablish power to a given power plant. The generators are housed in small, on-sight facilities that work in conjunction with a specific power station but are technically separate facilities. Most types of power stations, from hydroelectric to nuclear, have black start capabilities. Some, such as wind, which may not always have a constant and steady power source, are not, however.
Although black starts are rarely needed, they are a vital process in efficient power station functioning. Power failures can leave millions of people without power. Black start facilities allow relatively quick restoration of the power grid so effected areas can regain power more quickly.
Power stations wishing to become black start stations have to meet a rigorous set of criteria both before and after the black start facilities have been built. Only stations which are able to provide power to the overall grid once started are selected to become black start stations. Additionally, once the facility is installed, it should be able to perform multiple black starts without more than a few minutes of recharge time. This fast restart is important in case the initial start was incomplete or a failure. These kinds of facilities also need their own fuel source, so they can run at minimal power for several days if necessary.
Black start stations have their limitations since facilities started by black starts will not be running at full capacity. The facility still must rely on the complete connection of the other facilities in its grid in order to re-establish full power. These stations are used in several different countries, such as the United Kingdom, the United States, and Australia.