this service large power users such steel works, cold stores, large water pumping stations, can offer uk national grid. these contractors have frequency sensitive relays fitted incoming breakers, , these disconnect load if system frequency falls beyond pre-set figure (49.7 hz). these loads shed contracted period of @ least 30 minutes. within period standing reserve (reserve service) diesels of similar capacity (i.e., around 660 mw total) start up, , enable frequency service loads re-connected , relays re-armed.
frequency service designed cope loss of 2 660 mw sets in quick succession. there 2.25 gw of such frequency service loads available in uk cover peak demand of 60 gw.
if total reserve service payments, 2250 mw × £7,000 = £15.75 million divided total kwh delivered national grid customers, approximately 0.3 trillion kwh amounts total cost of 0.005p/kwh.
similar arrangements operate in united states , france , other large power grids.
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