What is it?

FCDM involves almost instantaneously interrupting the supply of electricity to large industrial loads in the event of a major grid ‘event’ e.g. a power station failure. It provides an immediate response to a sudden lack of supply or surge in demand which needs to be managed very quickly. Owners of large electricity consuming sites – such as cement kilns or smelting plants – will fit a relay to their loads which is triggered the moment the grid frequency drops below a certain value.

When is it used?

National Grid use this service as the last frequency-control backstop when the electricity grid frequency falls more than a given amount below 50Hz. The ‘trigger frequency’ for FCDM is typically 49.7Hz, but that may vary across contracts. Providers of FCDM will have their electricity supply automatically interrupted when the system frequency transgresses the low frequency relay setting onsite. FCDM-contracted loads are typically called upon 10-30 times per year.

FCDM service requirements

  • Provides the service within 2 seconds of an instruction
  • Delivers for a minimum of 30 minutes with suitable operational monitoring
  • Delivers a minimum of at least 3MW of service (can be several aggregated loads)