What is Frequency?
System frequency is a continuously changing variable that is determined and controlled by the second-by-second (real time) balance between system demand and total generation. If demand is greater than generation, the frequency falls while if generation is greater than demand, the frequency rises.
Why do we need to control Frequency?
National Grid has a licence obligation to control frequency within the limits specified in the 'Electricity Supply Regulations', i.e. ±1% of nominal system frequency (50.00Hz) save in abnormal or exceptional circumstances. National Grid must therefore ensure that sufficient generation and / or demand is held in automatic readiness to manage all credible circumstances that might result in frequency variations.
There are two types of Frequency Response Dynamic and Non Dynamic Response. Dynamic Frequency Response is a service used to manage the normal second by second changes on the system whereby the providers MW level dynamically moves with the frequency. Whilst a Non Dynamic Frequency Response service is triggered at a defined frequency deviation (i.e. the providers MW level changes at a defined frequency deviation).
What Services do we procure?
National Grid typically maintains System Frequency through three separate Balancing Services: