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G59 & G99 Regulations

We can assist in connecting any generation equipment to public distribution networks in compliance with both G59 and G99 requirements. We can help you assess whether the change in legislation is applicable to your generator system and if applicable ascertain the best technical method of upgrading your control system to comply.

What is G59?

G59 was introduced to protect the National Grid from receiving electricity from generators in a dangerous manner. The regulation is to prevent any generator from sending electricity onto the Grid without the knowledge and permission of the local electricity authority first.

As part of The Accelerated Loss of Mains Change Programme (ALoMCP), G59 has undergone some updates to bring this existing legislation up to the same standards as newer legislation. The current iteration G59 3.7 requires all non-domestic generators connected before 01 February 2018 to confirm that their generation equipment complies with ENA EREC G59/3-7. Compliance will improve network resilience and support wider initiatives helping meet the UK’s net zero targets.

All applicable generators must have protection settings compliant with EREC G59/3-7 by 01 September 2022, or they could be the subject of an enforcement programme. Generation owners have been encouraged to review their Loss of Mains (LoMs) protection settings to ensure compliance before last year’s deadline.

The requirements do not apply to a domestic or similar generator connected under EREC G83; it only applies to generators connected under EREC G59 before 01 February 2018.

What is G99?

G99 is a set of engineering recommendations created by the Energy Networks Association (ENA) for the connection of any form of generator, including diesel generators and renewable solutions, to run ‘in parallel’ or ‘synchronised’ with the UKs main electricity network.

The new regulations have been introduced in response to the rapid increase in renewable energy sources and the need to maintain the safety and security of supply when connecting these sources to the grid.


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