For large-scale renewable energy systems exceeding 1MW, a full G99 application must be submitted before installation to the Distribution Network Operator (DNO). These projects undergo detailed grid impact studies due to their potential effect on voltage stability, fault levels, and network reinforcement requirements.

What is a G99 Application for Systems Above 1MW?

The G99 standard applies to large-scale commercial and industrial renewable energy projects exceeding:

• 1MW+ generation capacity

• High-voltage (HV) grid connections

• Utility-scale solar farms, wind turbines, battery storage, and CHP

Due to their size, these installations require more extensive network studies and longer approval times to ensure they meet grid compliance standards.

What’s Required for a G99 Application Above 1MW?

Installer & Customer Details

• Company name & industry accreditation (e.g., MCS, NICEIC, RECC, or G99-certified installers)

• Installer and customer contact details

• Site address and project location details

System & Connection Details

• Type of renewable system (solar PV, wind, battery storage, CHP, hybrid)

• Total generation capacity (MW rating)

• Inverter manufacturer, model, and G99 compliance documentation

• Connection type (HV network, primary or secondary substation connections)

• Expected export capacity and grid constraints

Technical Documentation

• Detailed Single-Line Diagram (SLD) – connection layout to the DNO network

• Protection settings – voltage/frequency trip settings, anti-islanding, and G99 relay details

• Fault level contribution study – impact of the installation on network fault levels

• Power quality study & harmonic analysis (mandatory for larger installations)

• Earthing assessment – compliance with national safety standards

• Grid connection feasibility study (if required by the DNO)

• DNO application form specific to the network operator

Application Submission & Fees

• G99 applications for 1MW+ projects require advanced DNO assessment

• Application fees are significantly higher than smaller G99 projects

• Standard DNO processing time: 90+ days (3-6 months for grid studies)

• Grid reinforcement or infrastructure upgrades may be required

For large-scale projects, flexible export agreements or active network management (ANM) may be proposed by the DNO to manage grid constraints.

What Happens Next?

After submission, the DNO will:

• Conduct a grid impact assessment

• Approve the connection with or without conditions

• Request network reinforcement before approval

• Issue a Connection Offer Agreement (COA) outlining any required grid upgrades

• Once approved, installation can proceed

• A G99 commissioning report must be submitted post-installation

How Grid Guru Can Help?

At Grid Guru, we specialise in managing large-scale G99 applications, ensuring:

• All technical documentation is accurate and complete

• Fast-tracked application processing with DNOs

• Grid feasibility studies and network impact assessments

• Expert guidance on grid compliance and export agreements

If you need support with a G99 application for 1MW+ renewable installations, we’re here to help.