G99 Relay Testing & Compliance

The way we produce power in the UK has changed in recent years as we shift away from a reliance on large, fossil fuel-powered plants to smaller, more sustainable, renewable energy suppliers. Introduced in April 2019, G99 is a significant piece of legislation that contains specific operational and technical requirements for all providers who want to supply power to the network.

Whether you produce wind power, solar energy or hydro-electric power, G99 will impact the way that you connect to the network and interact with regulators. Here’s a summary of the main changes and challenges you face.

What is G99?

The increasing contribution of small-scale renewable energy providers to the grid poses a challenge to power providers. The larger the number of small suppliers, the less stable the network becomes – a situation that could cause damage to the generator and the grid itself.

Relays provide crucial protection for the system. Sitting between the generator and the grid, relays can decouple the system if there is a problem with either of them. Launched by the Energy Networks Association (ENA) on 27 April 2019, the “Requirements for connection of generation equipment in parallel with public distribution networks after 27 April 2019” significantly changes the way generators can be connected to the grid and operated. Often shortened to EREC G99, the new guidance replaced the previous G59 regulations. 

G99 was created to harmonise the technical and energy market rules across Europe to develop a safe, sustainable and competitive market for electricity. Existing operators can continue to work as usual, as G99 only applies to new power generation systems commissioned after 27 April 2019.

Types Of Relay

Within G99, there are two types of relay acceptable to regulators: Type Tested Interface Protection and Non-Type Tested Interface Protection.

A Type Tested Interface Protection has its protection settings fixed during manufacture. The regulations define Type-Tested Equipment as “a product which has been tested to ensure that the design meets the relevant requirements of G99.” All similar products will be built to the same exacting standards and meet the same levels of performance. 

Non-Type Tested Interface Protection systems need additional testing and measurements to assure the regulator that the protection you are using is robust enough.

Do I Need To Test My Relay?

In most cases, Type-Tested equipment should function correctly when fitted by a professional. In some cases, on-site protection commissioning tests may be required to demonstrate compliance with interface protection requirements.

If you use Non-Type Tested Interface Protection, then you are responsible for demonstrating that your relay conforms to all G99 requirements. 

Compliance with regulations can be assessed and recorded through a variety of ways, including:

• Calibration and stability tests on the overvoltage and under-voltage protection for each phase.
• Calibration and stability tests on the over frequency and under frequency protection.
• Calibration tests for the rate of change of frequency protection (if used).
• RoCoF and vector shift stability tests should on all Interface Protection relays.

How Do I Ensure Compliance?

The responsibility for managing G99 compliance rests with the person who wants to supply power to the network. If you’re using Non-Type Tested Interface Protection, it’s up to you to prove that it’s safe. To achieve the compliance requirements, Type A G99 generators need to include either one-off manufacturer’s information (including relevant data, simulation studies), or conduct and record on-site testing to establish safe operating levels. 

When completing G99 standard application forms, compliance for Type B, C and D power generating units, you must demonstrate and track the compliance process. The application form can be amended and updated as relevant information is recorded, and the functions and performance are demonstrated. 

Compliance data can come from a variety of sources, including correspondence, design data, manufacturer’s information, on-site testing, simulation studies, and type verification. Together they can demonstrate that your relay will perform under pressure.

Coping With Pressure

There is a simpler way to ensure G99 compliance. At Carter Sullivan, we can provide and configure a G99 converter that provides a critical fail-safe to protect you from power issues and overload. 

We take care of the certification and compliance process for all connection applications. Everything begins with a site survey where we discuss your requirements and begin to explore suitable options. We work in partnership with you to design a system and define its parameters to ensure it’s safe, secure and scalable. We’re then able to install and configure everything, taking care of the paperwork and any pressure. 

Click here to learn more about how Carter Sullivan can integrate Energy Storage into your business.