Page type: primary-anchored (mirrors Grid Code, Issue 6 Revision 36)
The Grid Code
The Grid Code is one of the 11 GB industry codes governing the electricity system. It is administered by NESO (the National Energy System Operator) and sets out the technical rules for connecting to and operating the National Electricity Transmission System. Every generator, network operator, DC converter owner, supplier, and non-embedded customer connected to or seeking connection with the transmission system must comply with the Grid Code.
Legal foundation: Electricity Act 1989, s.9; Transmission Licence Standard Condition C14.
Current version: Issue 6 Revision 36, effective 12 December 2025.
Source file: grid-code.md
Structure at a glance
The Grid Code contains 10 substantive sections, a glossary, and governance rules:
| Section | Code | What it does | Pages (approx) |
|---|---|---|---|
| Glossary & Definitions | GD | Defines ~500+ terms used throughout | 55 |
| Planning Code | PC | Data Users must provide for system planning | -- |
| Connection Conditions | CC | Technical rules for connecting plant | 95 |
| Compliance Processes | CP | How generators prove Grid Code compliance | -- |
| Operating Codes 1-12 | OC | Day-to-day operational procedures | ~200 total |
| Balancing Codes 1-3 | BC | Balancing Mechanism processes | -- |
| European Connection Conditions | ECC | Technical rules for EU Code Users (post-2019 generators) | 137 |
| Data Registration Code | DRC | Unified data requirements listing | -- |
| General Conditions | GC | Co-ordination and electrical standards | -- |
| Governance Rules | GR | Modification process and Review Panel | -- |
Bold = sections with dedicated sub-pages below.
Sub-pages
- Grid Code -- Connection Conditions (CC) -- the technical requirements for connecting generators, network operators, and demand to the transmission system. Includes CC.6.3, the core generator performance obligations.
- Grid Code -- Operating Codes (OC) -- the 10 active Operating Codes governing demand forecasting, outage co-ordination, testing, demand control, safety, contingency planning, and system tests.
Key concepts for non-specialists
What problem does the Grid Code solve? The transmission system only works if every piece of equipment connected to it behaves within known parameters. The Grid Code defines those parameters -- frequency range, voltage limits, fault clearance times, reactive power capability, and so on. Without it, a generator could connect plant that damages the network or destabilises the system.
Who must comply? Every User connected to the National Electricity Transmission System. In practice, the most burdensome obligations fall on generators (who must meet the CC.6.3 performance requirements) and on NESO itself (which must maintain system performance to the CC.6.1 standards).
CC vs ECC: There are two parallel sets of connection conditions. The original Connection Conditions (CC) apply to generators that connected before the EU network codes took effect (broadly pre-2019). The European Connection Conditions (ECC) apply to generators connecting under the retained EU Regulation 2016/631. Both remain in force. The ECC is structurally identical to the CC but adds EU-specific requirements (e.g. Type A/B/C/D classification by MW threshold, Fast Fault Current Injection).
How is it changed? Modifications are proposed using GCxxx numbers (e.g. GC0174). They are assessed by the Grid Code Review Panel (GCRP), which meets monthly. Routes include workgroup assessment, self-governance (for non-material changes), and Authority (Ofgem) direction.
Related instruments
- CUSC (Connection and Use of System Code) -- governs the commercial/contractual side of connection (charging, Bilateral Agreements). The Grid Code governs the technical side.
- BSC (Balancing and Settlement Code) -- governs settlement and trading. The Grid Code's Balancing Codes (BC1-3) interface with the BSC.
- SQSS (Security and Quality of Supply Standard) -- sets the planning and operational standards NESO must meet. The Grid Code CC.6 references the SQSS as "Licence Standards".
- STC (System Operator Transmission Owner Code) -- governs the NESO-TO interface. The STCP (SO-TO Code Procedures) sit under the STC, not the Grid Code.
- Engineering Recommendations -- G5/4 (harmonics), P28 (flicker) -- referenced by CC.6.1.
- EU Regulation 2016/631 -- Requirements for Generators; implemented via the ECC.
Defined terms
See the source file's defined terms register.
Cross-references
See the source file's cross-reference table.
Character positions
(None yet captured. This section will be populated when secondary sources referencing the Grid Code are ingested.)
Last updated: 2026-04-05