Grid Code

The Grid Code sets the technical rules for connecting to and using the GB transmission system. It covers voltage, frequency response, fault ride-through, protection, metering, and data submission. Every generator, interconnector, and demand user connected to the transmission network must comply. NESO administers the code.

The modification process

Anyone can propose a Grid Code modification. Once raised, it goes to the Grid Code Review Panel (GCRP), which assigns it to a Workgroup of technical experts. The Workgroup develops the solution and produces a report. NESO then runs a Code Administrator Consultation (CAC) so all affected parties can respond. After consultation, a Final Modification Report goes to the Panel, which votes and recommends to Ofgem. Ofgem makes the final decision unless the modification qualifies as Self-Governance, in which case the Panel decides.

Key concepts

• Self-Governance applies when a modification will not materially affect consumers, competition, or system security. The Panel decides; parties can appeal within 15 working days.
• Urgent modifications can skip normal timelines if Ofgem agrees the issue is time-critical. Ofgem determines urgency and sets the timetable.
• Cross-code impact means the modification affects other industry codes (CUSC, BSC, STC). When this happens, the codes must be changed in coordination.