Reserve Services and Frequency Response
National Grid is responsible for contracting short term generating provision to cover demand prediction errors and sudden failures at power stations. This covers a few hours of operation giving time for market contracts to be established to cover longer term balancing.
Frequency-response reserve acts to keep the system AC frequency within 1% of 50 Hz, except in exceptional circumstances. This acts on a second by second basis to adjust demand and provide some extra generation.
Reserve services are a range of services on differing response times:
- Fast Reserve: rapid delivery within two minutes of increased generation or reduced demand, sustained for a minimum of 15 minutes.
- Fast Start: units that start from standstill to deliver power within five minutes automatically, or seven minutes of a manual instruction, maintained for a minimum of four hours.
- Demand Management: reduction of demand of at least 25MW from large users of power, for at least an hour.
- Short Term Operating Reserve (STOR): generation of at least 3MW, from a single or aggregation of sites, within four hours of instruction and maintained for at least two hours.
- BM Start-Up: mainstream major generation units maintained in either an energy readiness or hot standby state.
These reserves are sized according to three factors:
- The largest credible single generation failure, which is currently either Sizewell B nuclear power station (1,260 MW) or one cable of the HVDC Cross-Channel interconnector (1,000 MW)
- The general anticipated availability of all generation plants
- Anticipated demand prediction errors
Read more about this topic: National Grid (Great Britain)
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