Black start

For a generating unit to start up, it must provide excitation power to the rotor. Many units utilize electricity from the grid for this purpose, which causes a problem restoring the grid if an outage has occurred. Black start units can start independently without electricity from the grid. System operators need to maintain a certain amount of black start to ensure their ability to restore the grid should there be an outage.

The location and capacity of black start units are key to a bulk system operator’s restoration plan following any outage. The units must be capable of providing real and reactive power to support frequency and voltage as the system is restored. Typical black start units include hydropower and fossil fuel power plants with a back-up generator. Black start may also be provided by batteries and certain distributed generation resources such as solar panels, fuel cells, and backup generators. 

In vertically integrated wholesale markets, black start is provided by utility resources under regulated cost-based tariffs. In competitive markets, the bulk system operator (the Independent System Operator or Transmission System Operator) contracts for black start services and the costs are charged out to loads.