Engineering recommendation G99
Engineering Recommendation (EREC) G99 covers the requirements for the connection of generation equipment in parallel with public distribution networks and is a legal requirement for certain generators connecting on or after 27 April 2019. You can connect generation compliant with G99 before this date, as compliance with G99 also ensures compliance with G59 requirements, which is the current standard. A new EREC G99 standard application form is also now available on the Energy Networks Association (ENA) website. The information below provides guidance on all aspects of the connection process for compliance with these requirements. We require Part 4 of the G99 generator standard application form to be completed at the initial submission stage if your power generating module is rated at 150 kW or greater.
Are there any exemptions?
Currently, energy storage technology is exempt from the requirements, and therefore do not need to comply with certain technical requirements of G99 and are not included in type definitions. However, the current requirements for energy storage under G59 will still apply. Additionally if your generating modules are <800W or you are making modifications to existing generation, you may be exempt. Please consult EREC G99 section 2.1 for further information.
How are generation types classified?
Type classification also depends on whether you are installing synchronous or asynchronous generation onto the network. Synchronous power generating modules are classified separately, as in the example below:
Image credit: Energy Networks Association
Generators are now classified into different types, of which there are four. In Great Britain, these four are as follows:
- Type A: 0.8kW to < 1MW and connecting at a voltage <110kV
- Type B: 1MW to <10MW and connecting at a voltage <110kV
- Type C: 10MW to <50MW and connecting at a voltage <110kV
- Type D: ≥ 50MW or connecting at a voltage ≥ 110kV
Each type carries a different set of requirements with which the generation must be compliant. The requirements of each type are cumulative, i.e. Type D generation must comply with the requirements of Type A, B and C generation in addition to the requirements of the Type D category.