G99 applications and compliance – the what, the why and the how

It’s coming up to 12 months since the new Engineering Recommendation G99 came into force on 27 April 2019. Any new power generation or storage plant being connected to the UK electricity network (and in some cases modifications to existing plant) must be designed and compliant with the new recommendation. We look at why G99 was needed and what these more complex requirements mean for projects.

The shift to distributed generation

Twenty years ago, electricity distribution was straightforward. In simple terms, there were huge coal, gas or nuclear power stations generating power which flowed through National Grid’s transmission network and into the distribution networks – and then used in homes, offices and factories.

Over the last ten years, the major shift towards renewables and energy storage has placed far more generation at the distribution network level (most often termed ‘distributed’ or ‘embedded’ generation). But this poses challenges for the network operators who need to ensure these distributed generators can stay connected safely, whilst supporting the energy system.

Network connection codes

The European Network of Transmission System Operators for Electricity (ENTSO-E) represents the 43 electricity transmission system operators (TSOs) from 36 countries across Europe. They have a wide legislative remit to support the optimal functioning of the EU energy market and the transmission network. This includes responsibility for developing Europe-wide network codes for any grid connections.

ENTSO-E established a need to harmonise the rules for grid connection for distributed generation to make a clear legal framework for grid connections, to safeguard system security, to ensure the safe integration of renewable electricity sources, and create a more efficient network for the benefit of consumers. As a result, they updated their network code for grid connection of generators. It is a legally binding document for all members.

The Energy Networks Association (ENA) represents the gas and electricity transmission and Distribution Network Operators (DNOs) in the UK and Ireland. The ENA write the engineering recommendations that these network operators must follow. To comply with ENTSO-E’s new legislation, the ENA had to update their existing engineering recommendations dealing with the connection of generators (EREC G59 and G83).

So, from 27 April 2019, “ENA Engineering Recommendation G99: Requirements for the connection of generation equipment in parallel with public distribution networks on or after 27 April 2019” (or G99 for short) and EREC G98 – came into force. G98 and G99 are now law in Great Britain.

What projects does G99 apply to?

Any power generation or storage plant being connected to the network, whether in front or behind the meter, on or after 27 April 2019, must comply with G98 or G99 and follow the new connection application process.

It’s important to note that schemes connected before 27 April 2019 under G83 or G59, but which are now undergoing a material change such as a new transformer, alternator or inverter may also need to comply with G98 or 99.

G98 is focussed on smaller generation capacities (up to and including 16 A per phase) such as roof-top solar on domestic houses or small offices or shops.

G99 covers all other generation – and is the area in which Roadnight Taylor specialise. There are different compliance requirements depending on the size of the generation and if it’s connected at low or high voltage.

  • Type A: 0.8 kW or above but less than 1 MW and connected below 110 kV
  • Type B: 1 MW or above but less than 10 MW and connected below 110 kV
  • Type C: 10 MW or above but less than 50 MW and connected below 110 kV
  • Type D: 50 MW or above connected at or greater than 110 kV

How does G99 now affect energy projects?

Anyone who wants a network connection that fits into Type A, B C or D above must fill in a G99 Standard Application Form (SAF)– or get an expert to do it for them – as the first stage in creating a G99 compliant project. As must anyone making a material change to a site commissioned before G99 was introduced.

G99 has far more requirements than G59, making the application stage more complex. Deep technical knowledge of the compliance requirements, and the proposed connection’s technical design, is therefore essential.

It’s crucial that you put in a good quality G99 application. A technically competent application should lead to a formal offer, but the wrong information could delay the process. Worse still if the offer is based on bad or incorrect application information, it could affect the viability of the project. For example, when you put in an application, it’s important to make sure the design is appropriate, the export capacity and import capacity are right and fault level contributions you declare are correct – otherwise your ability to develop the project could be limited.

While a lot of information is needed at the G99 application stage, a DNO can ask for more information at a later stage in the project and before it is commissioned. Any equipment bought for a project must be G99 approved, and further on-site testing may be required to demonstrate that the plant and overall site design is compliant once it is commissioned.

How we’re helping

Through our close relationships with all six of the UK DNOs, we know that few applicants are either designing compliant projects or are submitting G99 forms that have appropriate technical details.

As the G99 requirements are so complex, applications must be designed and drawn up by electrical specialists. Roadnight Taylor understands all the requirements and stages of G99. We can give advice on which type or class of generation you need and which requirements you need to comply with. We advise on plant design and create compliant connection applications, based on your preferred technology or equipment, that the DNOs will accept at the first time of asking.

Once you have received a connection offer, we can support you in the later stages of the project, and ultimately help you design and deliver an effective G99 compliant scheme.