The Black Start service is procured from generators that have the capability to start main blocks of generation from an on-site auxiliary generator, without reliance on external site supplies.
In the event of a Black Start, the service requires the provider to start up its main generator(s), carry out initial energisation of sections of the National Transmission System and distribution network, and support sufficient demand to create and control a stable power island. The Black Start generator may be required to provide start up supplies to other power stations as the system restoration progresses and will eventually be required to synchronise to other power islands. The restoration is initiated under the instruction of National Grid and proceeds under the general guidance of a site specific restoration plan.
National Grid is considering future alternative approaches for restoration. As part of this work two independent studies have taken place to investigate alternative options. The outcome of these studies can be found on the Energy Networks Association web site at the following link. National Grid are planning the next steps to take these outcomes forward.
Irrespective of the type of plant installed to provide a Black Start service, the following technical capabilities are required:
- The ability to start up the main generating plant (at least one unit/module) of the station from shutdown without the use of external power supplies, and be ready to energise part of the Network Electricity Transmission System or, if appropriate, the Network Distribution System within two hours of instruction from National Grid;
-The capability to accept instantaneous loading of demand blocks, ideally in the range 35 to 50 MW, and controlling frequency and voltage levels within acceptable limits during the block loading process (under these conditions, frequency can be within the range 47.5 to 52 Hz);
-The ability to provide at least three sequential Black Starts, to allow for possible tripping of the Transmission/Network Distribution System(s) during the re- instatement period or trips during the station's starting sequence itself;
- Back-up fuel supplies (e.g. distillate fuel), if appropriate, to enable the power station to run for a minimum duration, ideally in the range 3 to 7 days, following a Black Start instruction;
-Facilities to ensure that all generating units can be safely shutdown without the need for external supplies, and can be maintained in a state of readiness for subsequent start ups;
- The ability to maintain a high service availability on both the main and auxiliary generating plant (typically 90%); and
- The reactive capability to charge the immediate Transmission/Network Distribution System(s). This capability will depend on the local system configuration, but generating plant connected at 400kV or 275kV with a capability of at least 100MVAr leading (as measured at the commercial interface) should almost invariably meet this requirement. The generator must also be capable of withstanding the magnetic inrush and transient voltages associated with this charging duty.
Regular inspection and testing of all the associated station plant on both the main and auxiliary generating units is required. Testing is carried out in accordance with the Grid Code and the specific Commercial Services Agreement