G99 serves as both a regulatory framework and an application process for connecting specific types of electricity generation and storage units to the main electrical grid, ensuring safe and compliant integration.
G99 is the formal regulation and accompanying application process in the United Kingdom that governs the connection of various electricity generation devices to the main electrical utility grid. It primarily applies to integrated microgeneration and storage units.
Key Aspects of G99 Regulation
This regulation is crucial for ensuring that grid-connected systems operate safely and do not negatively impact the stability or quality of the electricity supply.
- Capacity Threshold: G99 specifically applies to generation units with a capacity exceeding 16 Amperes (A), which translates to 3.68 kilowatts (kW). Systems below this threshold typically fall under different, often simpler, regulations.
- Parallel Operation: It governs any form of generation device that runs in parallel or is synchronised with the main electrical utility grid. This means the system can generate electricity and feed it into the grid, or interact with it in a coordinated manner.
- Device Types: The regulation covers a broad range of generation technologies, including:
- Larger solar photovoltaic (PV) installations (e.g., commercial systems or large domestic arrays).
- Wind turbines.
- Combined heat and power (CHP) units.
- Battery energy storage systems (BESS) that can export power or operate in parallel with the grid.
- Other forms of microgeneration or distributed generation.
Why is G99 Compliance Essential?
Compliance with G99 is not just a legal requirement but also a critical measure for grid integrity and public safety.
- Grid Stability: It ensures that connected generation units do not cause disturbances to the grid's voltage or frequency, maintaining a stable and reliable power supply for all users.
- Safety: The regulations outline stringent technical requirements to prevent hazards such as islanding (where a section of the grid remains energised by local generation after the main supply is disconnected), which can pose a risk to utility workers.
- Operational Control: It allows the Distribution Network Operator (DNO) – the company responsible for operating the local electricity network – to be aware of and manage all generation sources connected to their grid.
The G99 Application Process
For systems falling under G99, a formal application must be submitted to the relevant DNO before the installation can be connected to the grid.
- Technical Information: The application requires detailed technical specifications of the generation equipment, including its protection settings, expected output, and how it will interact with the grid.
- DNO Approval: The DNO reviews the application to ensure compliance with G99 standards and assesses the impact the new generation will have on the local network. They may require network upgrades if the capacity is significant.
- Commissioning: Once approved, the system undergoes rigorous testing and commissioning in accordance with G99 requirements to verify its safe and correct operation.
Adhering to G99 is a prerequisite for connecting larger generation and storage systems, ensuring a harmonious and safe relationship between individual power producers and the broader electricity network.
