UK ENA G100 Issue 2 Export Limitation Scheme Compliance Guide

Key Takeaways

• ENA G100 Issue 2 details technical requirements for export and import limitation schemes applicable after 1 May 2023.
• Flexible connections, including export-limited ones, restrict capacity under specific network conditions.
• Loss of Mains (LoM) protection using vector shift must be updated to Rate of Change of Frequency (RoCoF) with specific settings.
• Non-compliance with LoM updates can lead to de-energisation of generation assets by your Distribution Network Operator (DNO).

What is ENA G100 Issue 2 and why does it matter for your solar installation?

ENA G100 details the technical requirements for customers' export and import limitation schemes. These rules apply to new generation installations in Great Britain after 1 May 2023. Compliance ensures your solar or energy storage system can connect to the public electricity network safely and without causing issues.

The Energy Networks Association (ENA) is the trade association for energy networks in Great Britain. Its members own and operate the electricity and gas infrastructure. The ENA develops engineering recommendations like G100, G98, and G99 to set standards for connecting generation equipment to the grid.

How export limitation works in Great Britain

When you connect a solar or energy storage system to the grid, your Distribution Network Operator (DNO) needs to ensure the local network can handle the electricity you might export. If the network cannot accommodate full export capacity, the DNO might require an export limitation scheme.

An export limitation scheme is a type of flexible connection. A flexible connection means your import or export capacity is restricted under certain conditions, such as network stress or faults. This allows for quicker and potentially cheaper connections by avoiding or deferring costly network upgrades. Export Limited connections are one of several types of flexible connections, which can be temporary or permanent.

G100 Issue 2 sets out the technical requirements for the devices and systems that manage these export limitations. This ensures that when your system needs to limit its export, it does so reliably and safely, protecting both your installation and the wider grid.

Understanding Loss of Mains (LoM) protection requirements

All generators connected to the distribution networks in Great Britain must have Loss of Mains (LoM) protection. This protection checks if your generator is still connected to the supply network. It is a critical safety feature.

The requirements for LoM protection have been updated. If your LoM protection uses vector shift, it must be removed or replaced. The updated requirement is to use Rate of Change of Frequency (RoCoF) protection. This change is a legal requirement and non-compliance breaches the terms of your connection agreement. The deadline for compliance with these updated EREC requirements was 1 September 2022.

LoM Protection RoCoF Setting

This updated setting helps the National Grid ESO operate the grid more efficiently and ensures your system disconnects quickly if the main supply is lost.

What you can check yourself, and what you cannot

You can check if your generation equipment's Loss of Mains protection has been updated to meet the RoCoF requirements. You should also verify that your export limitation device is registered and compliant.

However, you cannot change inverter settings or update LoM protection yourself. Work to update LoM protection should be carried out by an accredited G59 generation installer. Attempting to change grid-protection settings without proper accreditation can breach your connection agreement and create safety hazards.

If your equipment is already compliant with G59/3, you should notify your DNO by completing a specific form to update their records.

Consequences of non-compliance

Failure to comply with updated EREC G59 requirements for Loss of Mains protection can lead to serious consequences. Generators who are not compliant will be subject to an enforcement programme. This programme could ultimately result in the de-energisation of your generation assets.

Specifically, if no evidence of compliance is provided or is not sufficient to demonstrate compliance with the Distribution Code by Week 26 of the enforcement process, your DNO will make arrangements to de-energise your generation site's Connection Point in accordance with Distribution Code DGC12.

Finding compliant devices and information

Manufacturers are responsible for uploading and maintaining data and documentation for their products. The ENA hosts this data on behalf of its DNO members.

The ENA Type Test Register (TTR) closed on 16 April 2024. Its functionality and all held data have been migrated to Connect Direct. On Connect Direct, you can now register new devices, update existing devices, and register new users or manufacturers. This is where you would typically find information on devices that meet G100, G98, and G99 standards, including stand-alone G100 devices and export limiting devices.

What the published sources do not tell you

Statutory and engineering documentation confirms that G100 details technical requirements for export and import limitation schemes. However, it does not provide the specific technical requirements for G100 export limitation devices themselves. These details are typically found within the G100 guidance documents, which are not directly accessible from the provided sources.

Detailed information on the "Connect Direct" platform, including its specific features for G100 device registration and compliance assessment, is also not fully elaborated. The exact content of the "G98/G99/G100 Guidance Forms (PDF)" mentioned on the ENA Type Test Register page is not provided. Therefore, while the framework for compliance is clear, the granular technical specifications for devices are not publicly available in the provided sources.

This information is for general guidance only and does not constitute professional advice. For specific technical details or to ensure compliance, consult an accredited installer or your Distribution Network Operator.