Mandatory Frequency Response (MFR)
Mandatory frequency response (MFR) is an automatic change in active power output in response to a frequency change. The service helps us to keep frequency within statutory and operational limits.
Depending on their size and location, a power station may be obliged to have the capability to provide MFR. This requirement will be set out in their connection agreement and is summarised under Technical Requirements.
Providers may provider other balancing services, as long as doing so does no interfere with their ability to provide MFR.
Providers can offer one of these or a combination of different response times.
Primary response: Response provided within 10 seconds of an event, which can be sustained for a further 20 seconds.
Secondary response: Response provided within 30 seconds of an event, which can be sustained for a further 30 minutes.
High frequency response: Response provided within 10 seconds of an event, which can be sustained indefinitely.
Providers of MFR are required to have the following technical capabilities:
They must have a 3 to 5 per cent governor droop characteristic. Droop is defined in the Grid Code CC6.3.7 (C)(ii)) as: "The ratio of the steady state change in speed in the case of a Generating Unit, or in Frequency in the case of a Power Park Module, to the steady state change in power output of the Generating Unit or Power Park Module.”
They must be capable of providing continuous modulation power responses via synchronised generation through their automatic governing systems in order to counter frequency changes.
The requirements for MFR provision are summarised in the table below :
| NESO | Scottish Power | Scottish Hydro Electricity Transmission | |
|---|---|---|---|
| Small | < 50 MW | < 30 MW | < 10 MW |
| Medium | 50 MW =< 100 MW | N/A | N/A |
| Large | => 100 MW | => 30 MW | => 10 MW |
There is no tender process for this service as it is mandatory for large generators.
Testing
When a generating unit is built or modified, we must test its capability to provide MFR, this is part of the onboarding process when registering to a response service.
Mandatory Service Agreement (MSA)
The Mandatory Service Agreement (MSA) allows us to instruct the service as required.
When a generating unit is built or modified, we must test its capability to provide MFR. Once the generator has successfully met the minimum requirements, an MSA can be put in place, or amended if a unit has been modified
Once the generator has successfully met the minimum requirements, a Mandatory Service Agreement (MSA) can be put in place, or amended if a unit has been modified.
The MSA allows us to instruct the service as required.
Payments
Holding payment (£/h)
Holding payments are made for the capability of the unit to provide response when the unit has been instructed into frequency response mode.
Response energy payment (£/MWh)
Response energy payments remunerate the amount of energy delivered to and from the system when providing frequency response. This payment is set out in the Connection and Use of System Code (CUSC).
Price submissions
Generators submit their own prices for holding payments on a monthly basis via the Frequency Response Price Submission System (FRPS).
FRPS is available between the 5th and 15th working day of each month. Previously submitted prices are published on our website.
You can register and log in on the FRPS site here:
Monthly volume
The volume of MFR that has been dispatched each month is published in our capability report.
2024 engagement
Mandatory frequency response calendar
Mandatory frequency response information
FFR market information reports
Past frequency response system requirement
Settlements Frequency Data
The documents below contain weekly minute by minute frequency data.
Further enquiries
Get in touch with the right team within Balancing Services, who are on hand to answer any questions you may have.