UK ENA G99 Type D Large Scale Solar Grid Compliance Guide

Key Takeaways

• Utility-scale solar farms with capacity exceeding 50 megawatts in England are designated Nationally Significant Infrastructure Projects under Section 15 of the Planning Act 2008.
• Under Engineering Recommendation G99, generation units connected at 110kV or above, or with capacity of 50MW or more, are classified as Type D Power Generating Modules.
• High voltage connection applications require a formal 65-day assessment window from the operating DNO or Transmission Owner.
• Under statutory ESQCR Regulation 22, parallel operation requires agreeing specific requirements with the network operator and installing protective equipment to prevent network danger.
• Operating generation assets without proper licensing or statutory exemption is prohibited under Section 4 of the Electricity Act 1989.
• Owners bear ultimate legal responsibility for ensuring network authorisations are secured prior to energisation.

The Scope of EREC G99 Type D Generating Units

Engineering Recommendation G99 divides embedded generation into four operational categories (Type A, B, C, and D) aligned with European Network Codes.

Type D represents the largest category of power-generating equipment:

• Generators connected at 110kV or above, or with a registered capacity of 50 megawatts or greater.
• Because Type D plants interact directly with the national transmission system and bulk distribution networks, they must comply with the full requirements of the National Grid Electricity System Operator (NESO) Grid Code in addition to standard distribution rules.

Statutory Planning Thresholds: 50MW NSIP Classification

The development of large-scale solar in England intersects directly with national infrastructure planning law.

Under Section 15 of the Planning Act 2008:

• The construction or extension of an onshore generating station is within section 14(1)(a) only if the generating station is in England and its capacity is more than 50 megawatts.
• Solar farms exceeding this 50MW capacity threshold cannot be approved through standard Local Planning Authority planning applications; they require a Development Consent Order (DCO) granted directly by the Secretary of State.

High Voltage Application Windows and DNO Engagement

Large-scale solar projects connecting at 33kV, 66kV, or 132kV follow strict statutory interaction periods.

According to national guidance issued by the Department for Energy Security and Net Zero:

• Installers must submit the relevant Engineering Recommendation G99 application form (or G100 if export is limited) to the DNO before installing the device to ensure safe and effective operation of the electricity network.
• The DNO will be in touch within 45 days for low voltage energy devices and 65 days for high voltage energy devices to approve installation or request necessary system amendments.
• It is the energy device owner's responsibility to ensure that the DNO has received this notification and, in the case when the energy device is classified as apply to connect, granted authorisation before the work is carried out.
• Where equipment is not type-tested, the DNO may require additional documentation to demonstrate compliance with relevant engineering recommendations.

Primary Legal Framework: Electricity Act 1989 and ESQCR Regulation 22

Connecting utility-scale solar generation into the Great Britain grid involves compliance with fundamental energy legislation:

Electricity Act 1989 Licensing

Under Section 4 of the Electricity Act 1989, any person who generates or supplies electricity without a licence shall be guilty of an offence unless he is authorised to do so by a licence or exemption. Under Section 5, the Secretary of State may by order grant exemption from licensing requirements for specified classes of generation.

ESQCR Regulation 22 Parallel Operation Mandates

Under Regulation 22 of the Electricity Safety, Quality and Continuity Regulations 2002:

1. No person shall install or operate a source of energy which may be connected in parallel with a distributor's network unless he agrees specific requirements with the distributor who owns or operates the network.
2. The operator must have the necessary and appropriate equipment to prevent danger or interference with that network or with the supply to consumers so far as is reasonably practicable.
3. The generating plant must be configured to disconnect itself electrically from the parallel connection when the distributor's equipment disconnects supply to the installation.