Energy Sector Dictionary and Source Trail

Energy paperwork is dense because one sentence can carry a statute, a licence condition, an industry code and a technical standard at the same time. The dictionary gives each term a plain definition, then points to the instrument that gives the term its authority.

Scope: source-backed definitions for terms that recur across licences, codes, markets, networks and data standards.

Sources and standards

Every dictionary entry resolves to one of three primary-source categories: a statutory instrument on legislation.gov.uk (the Electricity Act 1989, the Energy Act 2023, the Data (Use and Access) Act 2025, the ESQCR 2002), a Standard Licence Condition of an Ofgem-issued licence (SLC 25.2 produces the Long Term Development Statement; CUSC, BSC, REC, SEC are the industry codes that govern the connection and trading rules), or a named technical standard (IEC 61968-13 and IEC 61970-301 for the Common Information Model; CGMES v3 with its application profiles; W3C SHACL for shape constraints).

How words carry weight in regulation

In energy regulation the exact word matters. A term written with a capital letter is usually a defined term: it carries one precise meaning set out in a definitions or interpretation section, and that meaning applies wherever the term appears. "X means Y" fixes the meaning exactly. "X includes Y" gives examples without limiting it.

The verb sets the force of a rule. "Must" and "shall" create a binding obligation, and modern drafting prefers "must". "May" grants permission or discretion. "Should" signals an expectation that is not strictly binding, and tends to appear in guidance rather than in law. "Have regard to" means a body must take something into account, not that it must follow it.

Instruments carry different weight. Acts of Parliament sit at the top, with regulations made under them. A licence is a statutory instrument in its own right, and its conditions bind the licensee; for a network company the RIIO price-control settlement lives in the Special Conditions of its licence. Industry codes bind the parties that sign up to them. Ofgem guidance is not law, but it sets out how the regulator will act, and a company that departs from it needs a good reason.

This is why every entry gives the plain meaning and the exact source. To read a rule correctly you need to know which instrument it sits in, whether the word is a defined term, and how strong the obligation is. The pattern holds across regulators: the Financial Conduct Authority Handbook marks a binding rule with an "R" and non-binding guidance with a "G".

How the most-used dictionary terms relate to each other, with edges showing the parent-child and reference links between instruments

Based on the Electricity Act 1989 Section 6 (the parent of the licensing regime), SLC 25.2 of the Electricity Distribution Licence (the parent of the LTDS), IEC 61970-301 and CGMES v3 (the parent standards of the data layer), and the Data (Use and Access) Act 2025 (the parent of the new data-protection vocabulary), the relationship graph below makes the connective tissue between the most-used dictionary terms visible. Nodes are coloured by cluster and edges are labelled with the kind of relationship (authorises, references, profiles, constrains).

Relationship graph of the most-used energy dictionary terms, with parent statutes, licence conditions, industry codes, technical standards, data-layer artefacts and operational vocabulary connected by labelled edges A layered relationship graph of the 31 most-used energy regulatory terms, arranged in five colour-banded horizontal tiers. From the top: statutory instruments (the Electricity Act 1989 Section 6, the Energy Act 2023, the Data (Use and Access) Act 2025 and the ESQCR 2002); the licence conditions Ofgem issues under them as the licensing authority (the distribution, transmission, generation and supply licences); the industry codes (the Distribution Code, Grid Code, Balancing and Settlement Code, CUSC, Retail Energy Code, Smart Energy Code and System Operator Transmission Code); the data-layer standards and profiles (IEC 61970-301 and IEC 61968-13 for the Common Information Model, CGMES v3, SHACL, RDFS, the BSI Engagement Hub, the LTDS, the EQ, SYSCAP and SCR profiles, and the GC0139 modification); and the operational vocabulary (G98 and G99, active network management, grid and bulk supply points, P29 and G5/5, MHHS and P478, and the BMRS settlement layer). Directed, labelled edges connect each instrument to the ones it authorises, references, produces, constrains, profiles or amends, tracing the parent-to-child topology down and across the tiers; every label sits on its own masking plate so the connectors stay readable. STATUTORY INSTRUMENTSLICENCE CONDITIONSINDUSTRY CODESDATA LAYER AND TECHNICAL STANDARDSOPERATIONAL VOCABULARY AND ENGINEERING RECOMMENDATIONSElectricity Act 1989 s.6Electricity Act 1989 s.6Energy Act 2023Energy Act 2023DUA Act 2025DUA Act 2025ESQCR 2002ESQCR 2002Ofgem (GEMA)Ofgem (GEMA)licensing authorityDistribution LicenceDistribution LicenceSLC 25.2 produces LTDSTransmission LicenceTransmission Licencetransmission owner dutiesGeneration LicenceGeneration Licencegenerator dutiesSupply LicenceSupply Licencesupplier dutiesDistribution CodeDistribution CodeGrid CodeGrid CodeBSC (Elexon)BSC (Elexon)CUSCCUSCRECRECSEC (DCC)SEC (DCC)STCSTCIEC 61970-301 (CIM)IEC 61970-301 (CIM)IEC 61968-13IEC 61968-13CGMES v3CGMES v3SHACL (W3C)SHACL (W3C)RDFSRDFSBSI Engagement HubBSI Engagement HubLTDS (publication)LTDS (publication)EQ / SYSCAP / SCREQ / SYSCAP / SCRGC0139 (modification)GC0139 (modification)G98 / G99G98 / G99ANMANMGSP / BSP / primaryGSP / BSP / primaryP29 / G5/5P29 / G5/5MHHS / P478MHHS / P478BMRS / settlementBMRS / settlementauthorisescreates NESOdata-protection termsLV voltage envelopereferencesreferencesreferences settlementconnection termsproducesbase ofDM extensionprofilesconstrainshosts artefactsamends Grid Codefeeds Distribution Code planningrefers to G98 / G99DPC4 covers ANMrefers to P29 / G5/5OC1: GSP voltageP478 authorises MHHS migrationBMRS publishes

The graph shows the parent-child and reference relationships, not the full set of cross-links inside each cluster. A reader using the dictionary entry for any node sees the full neighbour list with the citation tag for each link. The colour bands match the cluster sections above and the dictionary search filter set.

Primary sources for every dictionary entry

The most load-bearing parent sources are listed below. Each is recorded with its document title, publication date, the locator paragraph, and, where available, the exact wording quoted from the source.

  1. SLC 25 of the Electricity Distribution Licence (Long Term Development Statement). The condition that produces the LTDS at intervals of not more than seven years; SLC 25.2 specifically authorises Ofgem to give directions on content and form. https://epr.ofgem.gov.uk/Content/Documents/Electricity Distribution Consolidated Standard Licence Conditions - Current Version.pdf
  2. Electricity Act 1989, s.6(1)(c). The statutory parent of the licence regime under which every other instrument cited above is held. https://www.legislation.gov.uk/ukpga/1989/29/section/6
  3. Data (Use and Access) Act 2025. Royal Assent 19 June 2025; the parent statute of the new smart-data and data-protection vocabulary entered into the dictionary in early 2026. https://www.legislation.gov.uk/ukpga/2025/18
  4. Data (Use and Access) Act 2025 (Commencement No. 5) Regulations 2026. SI 2026/31; first 2026 commencement order for the Data (Use and Access) Act 2025. https://www.legislation.gov.uk/uksi/2026/31/made
  5. Data (Use and Access) Act 2025 (Commencement No. 6) Regulations 2026. SI 2026/82; majority of Part 5 data-protection provisions in force 5 February 2026. https://www.legislation.gov.uk/uksi/2026/82/contents/made
  6. LTDS CIM Stage 2 and 3 Extension (Derogation) Letter, dated 13 May 2026. Signatory: Steve McMahon, Director, Network Price Controls. Confirms BSI CIM Engagement Hub as official location of record for LTDS data-exchange definition artefacts; introduces the SCR profile. https://www.ofgem.gov.uk/sites/default/files/2026-05/LTDS-CIM-Stage-2-and-3-Extension-Derogation-Letter.pdf
  7. The Grid Code, NESO. Issue 6 Revision 37, 13 April 2026. Parent of the Grid Code section vocabulary (OC1 voltage management, BC1 balancing). https://www.neso.energy/industry-information/codes/grid-code-gc
  8. The GB Distribution Code, Issue 59, 24 April 2026, Distribution Code Review Panel. Parent of the Distribution Code section vocabulary (DPC4 voltage management, DPC5 connection requirements). https://www.dcode.org.uk/
  9. ENA G98 Issue 2, 10 March 2025. Requirements for connection of Fully Type Tested micro-generators up to 16 amperes per phase. Parent of the G98 entries in the dictionary. https://dcode.org.uk/assets/250307ena-erec-g98-issue-2-(2025).pdf
  10. ENA G99 Issue 2, 10 March 2025. Requirements for connection of generation equipment in parallel with public distribution networks; Types A, B, C, D. Parent of the G99 entries. https://dcode.org.uk/assets/250307ena-erec-g99-issue-2-(2025).pdf
  11. ENA P29 working group, Distribution Code Review Panel. Issue 1 (1990) holds the 2 percent at 132 kV and below voltage-unbalance limit; the revision in progress is the parent of the updated entries. https://www.dcode.org.uk/working-groups/erp29-working-group
  12. IEC 61970-301. CIM base model; canonical source for ConductingEquipment, EquivalentInjection, ACLineSegment and the rest of the class vocabulary the LTDS profiles refer to. https://webstore.iec.ch/publication/64022
  13. IEC 61968-13. CIM distribution-management extensions; parent of the medium-voltage and low-voltage class vocabulary the GB distribution licensees use. https://webstore.iec.ch/publication/65122
  14. CGMES v3. ENTSO-E Common Grid Model Exchange Standard; the European profile family the GB regime adopted under the 2024 Ofgem Direction. Parent of the EQ, SYSCAP, SSH, TP, SV, SCR and Header profile entries. https://www.entsoe.eu/digital/cim/cim-conformity-and-interoperability/
  15. CGMES Application Profiles Library. The library that holds the named profiles the LTDS uses. https://www.entsoe.eu/digital/cim/cim-for-grid-models-exchange/
  16. Grid Code Modification GC0139, NESO and Ofgem. Enhanced Planning-Data Exchange to Facilitate Whole System Planning; the modification that brings the GB Grid Code into line with the CGMES v3 directive Ofgem issued in 2024. https://www.neso.energy/industry-information/codes/gc/modifications/gc0139-enhanced-planning-data-exchange-facilitate-whole-system-planning
  17. BSI CIM Engagement Hub. Gated portal; the official location of record for LTDS data-exchange definition artefacts confirmed in the 13 May 2026 derogation letter. https://cim.bsigroup.com/
  18. Capacity Market Final Auction Parameters letter, DESNZ to NESO, February 2026. Parent of the Capacity Market entries; T-4 2029/30 cleared at twenty seven pounds ten per kilowatt year for forty point one gigawatts. https://www.gov.uk/government/publications/capacity-market-auction-parameters-letter-from-desnz-to-neso-february-2026
  19. NESO Data Portal. NESO Open Licence. Parent of the BMRS and operational-data entries. https://www.neso.energy/data-portal
  20. Market-wide Half Hourly Settlement Programme, Elexon. Parent of the MHHS, P478 and milestone entries. Migration began 22 October 2025; Milestone 15 in May 2027; cutover Milestone 16 in July 2027. https://www.elexon.co.uk/bsc/operational/market-wide-half-hourly-settlement/
  21. BSC Modification P478 (MHHS). The Balancing and Settlement Code modification that authorises the MHHS migration. https://www.elexon.co.uk/bsc/mod-proposal/p478/

The remaining one hundred and ninety nine dictionary entries each resolve to one or more of the primary sources listed above.