Updating your LoM protection

Updating your Loss of Mains protection

Find out how to update your Loss of Mains (LoM) protection to become compliant with the updated Engineering Recommendation G59 requirements, or notify us if your equipment is already compliant.

The Accelerated Loss of Mains Change Programme (ALoMCP) update

The Accelerated Loss of Mains Change Programme (ALoMCP) was in place between October 2019 and August 2022 and during this time helped to fund thousands of generator owners to make the necessary changes to their Loss of Mains protection before 1 September 2022. Please note the programme is now closed to new funding applications, however, all generation owners are still required to ensure their equipment is compliant to avoid facing enforcement action. View our latest programme updates here.


What are the setting changes required in the updated Engineering Recommendation (EREC) G59?

All generators that are connected to the distribution networks in Great Britain have Loss of Mains (LoM) protection, one of the many protection requirements on the electricity system.

This applies to generating plants that run in long term parallel with the distribution network and are within scope of Engineering Recommendation (EREC) G59, regardless of the type of generator, such as solar, wind or gas. Loss of Mains is designed to check if a generator is still connected to the supply network. 

Where LoM is provided by vector shift, it must be removed and/or replaced with Rate of Change of Frequency (RoCoF).  RoCoF is the rate at which frequency changes and is used to detect the absence of the connection to the system and disconnects the site if that RoCoF exceeds a specific value. The RoCoF setting requirement has been changed to 1Hz/s with a definite time delay of 500 milliseconds.  It will mean National Grid ESO will be able to operate the grid more efficiently.

For more information on Loss of Mains protection and guidance on identifying if your equipment is compliant, see our helpful Loss of Mains guide.

The date for compliance with these updated EREC requirements was 1 September 2022.

Next steps

Generator owners who have not applied for funding, nor already informed us that they are already compliant, will be contacted to establish their current compliance status and will be required to cover the costs associated with the necessary changes. If you believe your equipment is already compliant, please complete this form. This will enable us to update our records and will stop us from contacting you unnecessarily. Any generators who are not compliant and therefore require updates to their protection will  be subject to an enforcement programme which could ultimately result in the de-energisation of generation assets. 


Enforcement process from 1 September 2022

LoM enforcement process screenshot.JPG

Week 0: Written notification sets out to generator owner the non-compliance or unknown status of their generator site and sets out the actions to address non-compliance.

Week 4: Written notification sets out whether a response has been received to the first notice. If no response is provided then a physical, durable copy of the notification will be attached at, or as close to, the generator site as possible. The notification will repeat the actions to address non-compliance.

Week 8: Repetition of second notice: written notification sets out whether an appropriate response to non-compliance has been provided. If no response is provided, another physical copy of notification attached at, or close to, the generator site.

Week 16: Repetition of second notice.

Week 22: Repetition of second notice.

Week 26: If no evidence of compliance provided or evidence is not sufficient to demonstrate compliance with the Distribution Code, the DNO will make arrangements to de-energise the generation site’s Connection Point in accordance with Distribution Code DGC12.

Frequently asked questions

Useful links

Is your site already compliant?

Please notify us if your site is already compliant with G59/3 so that we can mark your site as compliant.

Notify us

A guide to Loss of Mains protection

View our guide for more information on inverters and relays and how to check if your site is compliant.

Read more

Check your compliance

You can use the self-serve tool on the Futureproof Your Power website to check if you need to upgrade your equipment.

Read more

ENA Manufacturer Knowledge Base

Browse a list of manufacturers that have declared their equipment as either compliant or non compliant with the changes.

Read more

Accelerated Loss of Mains Change Programme (ALoMCP)

The ALoMCP is now closed to new funding applications but you can still view our programme updates and reports.

Read more

Get in touch

If you have any queries relating to Loss of Mains protection please get in touch with our team who will be more than happy to help.

Get in touch