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Last edited 20 Jan 2022
Engineering Recommendation G99
Engineering Recommendation G99, or EREC G99, was issued by the Energy Networks Association (ENA) in July 2018 and came into effect on 27 April 2019. It applies to organisations involved in developing generation projects that are connected to the grid. It also affects how different types or configurations of equipment must comply with the requirements.
EREC G99 was published by the ENA to replace EREC G59. After 27 April 2019, organisations were longer legally permitted to connect certain types of power generation equipment that was solely compliant with G59.
 Changes brought about by EREC 99
EREC 99 established more stringent operating parameters for all new generation equipment 1MW (or larger) that would be connected to public distribution networks of licensed Distribution Network Operators (DNOs). It also changed the application process for this type of equipment and put new compliance and commissioning requirements in place.
Under EREC G99, this type of equipment must provide frequency response in either Limited Frequency Sensitive Mode (LFSM) or Frequency Sensitive Mode (FSM) to control active power output in response to frequency changes on the grid.
Generators over 1MW must also include:
- Fault ride through to keep them connected when there are significant voltage depressions due to faults on the grid.
- Fast fault current injection to support the system during a fault by quickly injecting reactive current in order to keep the grid voltage from dropping too low.
- Voltage control systems that can inject or absorb reactive power into the grid to control voltage.
- Enhanced variable reactive power capabilities.
- Testing and protection capabilities previously handled by large grid code compliant power stations.
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