LTDS: Long Term Development Statements

What is an LTDS?

A Long Term Development Statement is the regulatory instrument through which each of the 14 distribution licence areas in England, Wales, and Scotland publishes detailed network data. It contains interconnected datasets that show whether your local network has capacity for new generation or demand. Under Standard Licence Condition 25 (SLC25) of the electricity distribution licence, every DNO must publish and maintain an LTDS. Click the layers below to discover what information each one holds.

What it contains

Network diagrams, substation ratings, maximum demand data, generation already connected, firm and non-firm capacity, fault levels, and planned investment. The minimum content is prescribed by Standard Licence Condition 25 of the electricity distribution licence and the Form of Statement issued by Ofgem. Since 25 November 2024, all LTDS publications must provide grid model data using the Common Information Model (CIM) and capacity heatmaps, following Ofgem's LTDS Direction.

Why it matters for connections

If you want to connect generation or significant demand, the LTDS tells you whether there is spare capacity at your nearest substation. If there is no spare capacity, you will need to pay for reinforcement or accept a non-firm (curtailable) connection. The connection queue data shows you how many other projects are already waiting. Without consistent, machine-readable LTDS data, developers are forced to navigate fragmented, often PDF-based information that creates real barriers to connections, planning and wider system coordination.

The core problem LTDS reform is solving

The issue we started with was not a simple reporting gap. It was a fragmented, largely non-machine-readable set of network information, often locked in PDFs, inconsistent across DNOs and difficult for stakeholders to use in any meaningful way. What we are now building through LTDS is a transition away from that towards structured, interoperable, machine-readable data using CIM, with a clear pathway from current state to target state that the whole sector can realistically deliver.

The regulatory journey

LTDS reform has been a multi-decade effort. From the original SLC25 obligation through to the 2024 Direction requiring CIM grid model data, each milestone reflects a step-change in what is expected of distribution network operators. This timeline shows the key regulatory moments.

Understanding CIM

The Common Information Model (CIM) organises physical grid data into a hierarchy of containers. Think of it like a postal address: a region contains substations, each substation contains voltage levels, and each voltage level contains the actual equipment (transformers, cables, breakers). This tree structure means every piece of equipment has a unique location in the model. The diagram below shows how the key CIM classes relate to each other.

Think of it like a postal address

A SubGeographicalRegion is like a county. A Substation is like a building on a street. A VoltageLevel is like a floor in that building. And the equipment (transformers, cables, breakers) are like the rooms on that floor. Every piece of equipment has a unique address in this hierarchy, which means anyone reading the data can find exactly where it sits in the network. This structure is what makes CIM data interoperable: two different software systems can understand the same model because they share the same addressing scheme.

Why CIM, and the GB CIM profile

CIM is an internationally recognised IEC standard (IEC 61970/61968) enabling consistent machine-readable data exchange across transmission and distribution systems. Moving to CIM allows network data to be structured, validated, and exchanged using a shared ontology. But CIM alone is not enough. A national profile is needed.

The interoperability problem

Multiple CIM implementations internationally diverge on naming conventions, equipment parameters, and exchange artefacts. ENTSO-E maintains the Common Grid Model Exchange Specification (CGMES) for transmission. Nordic TSOs and continental DNOs use variants aligned to their market arrangements. These differences prevent direct model interchange without a national schema extension. Without a common GB profile, each DNO could implement CIM differently, recreating the fragmentation problem in a new format.

The GB CIM profile for LTDS

Ofgem, in consultation with ENA and industry, established a CIM profile for LTDS based on a GB CIM information model. This profile builds on CGMES v3 but includes LTDS-specific extensions to ensure consistency across all DNOs and interoperability with NESO's whole-system models. The GB-specific extensions cover fuel types, seasonal rating limits, LTDS equipment details, system fault levels, and load forecasts, none of which exist in the base CGMES specification.

Aspect	Base CGMES v3	GB CIM LTDS Profile
Scope	Transmission system exchange (TSO-TSO)	Distribution-to-transmission and distribution-to-stakeholder
Maintained by	ENTSO-E	BSI (under Ofgem governance) with ENA input
Fuel type modelling	Generic GeneratingUnit only	Extended with LTDS-specific fuel type enumerations
Seasonal limits	Single rating	Seasonal and cyclic rating limits per equipment
System fault levels	Not included	Included with make/break levels per busbar
Load forecasts	Snapshot only	5-year forecast profiles with growth scenarios
Validation	QoCDC rules (ENTSO-E)	SHACL constraints with GB-specific severity rules
Profiles defined	EQ, SSH, TP, SV, DL, GL, SC	EQ, SSH, TP, SV, DL, GL, SC plus SYSCAP (system capacity)

LTDS CIM profile architecture

Stage 1.3 artefacts (November 2025)

The Stage 1.3 release is the current baseline for LTDS CIM data. All artefacts are hosted on the BSI Engagement Hub. Only Equipment (EQ) profile data is required at this stage. No Short Circuit, Geographical Location, Steady State Hypothesis, Topology, State Variable, System Capacity or Diagram Layout profile data is included yet. No capacity heatmap data is in scope for Stage 1.3.

G1

Grid Modelling Annex 1: Grid Modelling Guidelines

How DNOs should model their distribution networks in CIM, including equipment naming, container hierarchy, and modelling conventions.

Version 5
G2

Grid Modelling Annex 2: Data Exchange Specifications

File formats, packaging, metadata headers, and exchange protocols for submitting LTDS CIM data.

Version 5
A1

Appendix 1: CIM100v111 UK LTDS AllProfiles

The full Enterprise Architect information model defining all CIM classes, attributes, and relationships for the GB LTDS profile.

Version 8 (Enterprise Architect .eap)
A2

Appendix 2: Information Model Extension Definitions and Diagrams

GB-specific extensions to the base CIM model, including fuel type enumerations, seasonal limits, and LTDS equipment details.

Version 3
A3

Appendix 3: LTDS Profiles in RDFS

Machine-readable profile definitions in RDF Schema format. Covers all 8 profiles: EQ, SC, GL, SSH, TP, SV, DL, and SYSCAP. These define which CIM classes and properties have meaning within LTDS.

7 profile files
A4

Appendix 4: Difference Profile Definitions and Diagrams

Documents the delta between the base CGMES v3 model and the GB LTDS profile, making it clear what has been added, modified, or constrained.

Version 4
A5

Appendix 5: Merged Profile Class and Attribute Lists

Consolidated spreadsheet listing every CIM class and attribute used across all LTDS profiles, with cardinality and datatype.

Version 5
A6

Appendix 6: Constraints in SHACL

The complete SHACL constraint ruleset for the Equipment (EQ) profile (Edition 6). Expresses validation rules for attribute ranges, required associations, subtype checking, and cross-object relationships.

EQ Edition 6 (complete ruleset)
A7

Appendix 7: Constraints Descriptions

Human-readable documentation of each SHACL constraint, explaining what it checks, why it matters, and what severity level applies.

Version 4
PN

Stage 1.3 Publication Notes

Release notes explaining what changed between Stage 1.2 and 1.3, including scope decisions, known issues, and applicability guidance.

Version 1
AP

Stage 1.3 Artefact Applicability

Matrix showing which artefacts apply to which DNOs and which profiles are in scope for Stage 1.3 submissions.

Version 1

All Stage 1.3 artefacts are published on the BSI Engagement Hub: cim.bsigroup.com/releases/ltds/november-2025/

DNO LTDS data status

Find your DNO and see whether they publish LTDS data in machine-readable format. All 14 licence areas are required to provide CIM-format data following the 25 November 2024 LTDS Direction. Click any DNO to see format details, coverage, and Stage 1.3 readiness.

How SHACL validation works

Machine-readable LTDS data is only useful if it is consistent and complete. SHACL (Shapes Constraint Language) is the W3C standard used to validate LTDS CIM data against the GB profile rules. The Stage 1.3 SHACL constraints (Appendix 6) provide the complete EQ Edition 6 ruleset. Understanding how validation works is critical for anyone producing or consuming LTDS data.

What RDFS profiles define

The RDFS profiles (Appendix 3) define which CIM classes and properties have meaning in LTDS. They act as a vocabulary: if a class or attribute is not in the RDFS profile, it is not part of LTDS. This boundary ensures that only relevant data is exchanged and validated.

What SHACL constraints express

SHACL constraints go beyond vocabulary to express complex rules: attribute value ranges (e.g. voltage must be positive), subtype selection (e.g. GeneratingUnit must be associated with a valid fuel type subclass), cardinality (e.g. exactly one BaseVoltage per busbar), and cross-object relationship checking (e.g. every SynchronousMachine must link to an appropriate GeneratingUnit subtype).

1

Define the expected shape

A Substation MUST have a name (string), a region association (SubGeographicalRegion), and contain at least one VoltageLevel. Each VoltageLevel MUST have a BaseVoltage association with a positive nominal voltage value.

2

Load actual LTDS CIM data

Your LTDS CIM/XML file is parsed into an RDF graph. Each equipment record becomes a graph node with typed properties. The RDFS profiles determine which nodes and properties are in scope for validation.

3

Validate against SHACL shapes

Each graph node is checked against its corresponding SHACL shape. Does it have all required associations? Are the data types correct? Are numeric values within the valid range? Are the right subtypes used? Missing, invalid, or out-of-range values are flagged with a severity level.

4

Generate validation report with severity levels

The validation report classifies each finding by severity. Violation means required data is missing, wrong datatype, or cardinality is violated. Warning means undefined data is present or soft guidance is not followed. Info means uncommon but valid data patterns are detected.

Violation: required rule broken

Warning: soft guidance not followed

Info: uncommon but valid

Sample validation output (based on known SHACL messages)

Pass: Substation GN001 has valid name, SubGeographicalRegion association, and contains VoltageLevel with BaseVoltage at 11 kV.

Warning: PSRType.name=BSP not found in this dataset. This is expected in Scottish licence areas where Bulk Supply Points do not exist in the distribution network model.

Violation: SynchronousMachine SM-0042 is not associated with an appropriate GeneratingUnit subtype. Expected one of: ThermalGeneratingUnit, HydroGeneratingUnit, WindGeneratingUnit, SolarGeneratingUnit, NuclearGeneratingUnit.

Warning: BaseVoltage association present for ACLineSegment in circuit section outside substation container. This is valid but uncommon; verify whether the circuit component is correctly associated with a Line container rather than a Substation container.

Info: ACLineSegment AS-CONN-0003 has very short length (0.5m) with thermal limit set to 9999 MVA. This pattern is recognised as a modelling workaround for very short connectors with no operational constraints.

Known data population workarounds

Very short connectors with no operational constraints are modelled as ACLineSegments with dummy high thermal limits (e.g. 9999 MVA). This is a recognised workaround in the Grid Modelling Guidelines.

Protected switches in circuits may be associated with Substation containers instead of Line containers. This is an artefact of how some GIS systems export circuit topology and does not affect electrical connectivity.

Try the mock validator

Select your DNO and a data category to see how validation results are presented. This demonstrates the type of quality checks that the real SHACL validation engine performs against the EQ profile constraints defined in Appendix 6.

DNO Group

Data Category

From PDFs to machine-readable data

LTDS data was historically published as PDF documents that were nearly impossible to analyse for connection feasibility. The issue was not just the format. It was a fragmented, largely non-machine-readable set of network information, inconsistent across DNOs and difficult for stakeholders to use in any meaningful way.

Today, standardised electronic formats use the Common Information Model (CIM) per IEC 61970/61968 and Common Grid Model Exchange Specification (CGMES) per ENTSO-E, allowing computers to read, validate, and analyse the data automatically. The GB CIM profile for LTDS builds on CGMES v3 with extensions for fuel types, seasonal limits, equipment details, fault levels, and load forecasts. These technical artefacts are hosted on the BSI Engagement Hub (Stage 1.3 published November 2025), providing a single source of truth for the LTDS data model.

The standardisation of LTDS data also supports the Centralised Strategic Network Plan (CSNP) methodology. The CSNP provides a unified view of network investment needs across distribution and transmission systems. Without consistent, machine-readable LTDS data from all 14 licence areas, the CSNP would have no reliable inputs.

Why this matters

If your DNO publishes machine-readable LTDS data using the GB CIM profile, you can answer your most important questions in minutes: Is there spare capacity at your substation? What are the fault levels? Who else is connected ahead of you? Machine-readable data saves time and money for developers and improves outcomes for everyone connected to the distribution network.

Connection applicants

Developers and network users rely on timely, accurate LTDS data to understand constraint locations, maximum demand forecasts, and planned reinforcements. Standardised CIM data reduces delays in the connection application process and enables automated feasibility screening.

Flexibility providers

Constraint locations and network capacity information directly inform where flexible generation or demand-side resources are most valuable. Capacity heatmaps (coming in future stages) will make this even more accessible.

Regulators

Ofgem can compare investment plans, asset conditions, and network capability across all 14 licence areas. Standardised CIM data supports evidence-based policy decisions and network resilience oversight under RIIO-ED2. SHACL validation ensures data quality is measurable and comparable.

System operator (NESO)

NESO uses DNO LTDS data to forecast transmission system requirements and plan bulk system upgrades. CIM interoperability between distribution and transmission models is essential for whole-system planning. The GB CIM profile ensures distribution data can feed directly into NESO's models.

Academics and innovators

Open, standardised network data enables research into network planning, demand prediction, and optimal placement of distributed resources. The RDFS and SHACL artefacts on the BSI Engagement Hub provide a structured foundation for building analysis tools.

Data standards bodies

BSI maintains the LTDS CIM artefacts under Ofgem governance. A lot of the progress reflects the depth of technical expertise from industry contributors, the discipline and structure introduced through BSI governance, and the increasingly important role of stakeholder engagement through the Engagement Hub.

GC0139: The transmission side

LTDS covers how DNOs publish distribution network data outward to developers and stakeholders. But there is a parallel reform happening on the transmission side. GC0139 is a Grid Code modification that establishes a structured, CIM-based exchange of power system models between DNOs and NESO. Together, LTDS and GC0139 create the data infrastructure for whole-system planning.

What is GC0139?

GC0139: Enhanced Planning-Data Exchange to Facilitate Whole System Planning replaces the existing ad-hoc planning data obligations with a structured bilateral exchange of solved power system models (PSMs) in CIM format. Network Operators send sub-transmission models to NESO, and NESO sends Transmission System models back. This two-way exchange happens twice a year, enabling coordinated network planning across the transmission-distribution boundary for the first time.

Why it matters

Without GC0139, NESO cannot build a complete whole-system model of the electricity network. Distribution networks now host significant volumes of generation (solar, wind, battery storage) that affect transmission system flows. The current approach of exchanging spreadsheets and PDFs between DNOs and NESO does not support the power flow analysis needed for coordinated planning. GC0139 provides the structured data exchange mechanism to solve this.

Proposer

Ian Povey (Electricity North West). Code Administrator Chair: Jess Rivalland (NESO). Proposal form submitted 12 February 2020.

28 workgroup meetings

Workgroup Report published 3 December 2025. Unanimous vote that the Original Proposal better facilitates Grid Code Objectives than the Baseline.

Final Mod Report

Draft Modification Report: 18 February 2026. Final Modification Report: 10 March 2026. Code Administrator Consultation ran 6 January to 6 February 2026.

Implementation

10 business days after Authority decision. New obligations from 1 January 2027. High impact on NESO, Transmission Owners, DNOs, and IDNOs.

PC.9: Network Operators to NESO

Network Operators provide sub-transmission Power System Models (PSMs) to NESO at weeks 2 and 28 each year. Models cover the sub-transmission network (typically 132 kV in England and Wales, 33 kV in Scotland), direct connections, lower voltage equivalents at boundaries, and generation aggregated by energy source. Two scenarios: NETS minimum demands and NETS peak demands.

PC.10: NESO to Network Operators

NESO provides Transmission System PSMs back to Network Operators at weeks 12 and 38. Models include switch-level Transmission model, equivalence of rest of system at boundary nodes, and generation/HVDC modelled as equivalents. Scenarios include peak demand, summer minimum, solar-peak, maximum fault level, and national high/low power transfer dispatch.

LTDS vs GC0139 comparison

Dimension	LTDS	GC0139
Regulatory instrument	SLC25 (Distribution licence)	Grid Code (Planning Code PC.9, PC.10)
Proposer / owner	Ofgem	Ian Povey (ENWL), NESO workgroup
Who publishes	14 DNOs (outward to stakeholders)	DNOs and NESO (bilateral exchange)
Who consumes	Developers, stakeholders, NESO	NESO + DNO planning teams
Data content	Equipment topology (EQ profile)	Solved power system models (PSMs)
CIM base	CGMES v3 + GB LTDS extensions	CGMES v3 + GB transmission extensions
Exchange frequency	Annual (November cycle)	Twice yearly (weeks 2/28 and 12/38)
Status (Mar 2026)	Stage 1.3 live (EQ profile only)	Final Mod Report published, awaiting Authority decision

Four types of Power System Model data

Structural

System components and their characteristics: transformer ratings, voltage limits, cable impedances, switch types. Describes what the network is built from.

Diagram

Visual representation of structural data. Network diagrams showing how equipment connects. Used for human review and validation of model topology.

Situation

Operating state at a point in time: customer demand levels, stored energy, switch positions, generator dispatch. Describes what the network is doing right now.

Solution

Analysis results from power flow studies: active and reactive power flows on every branch, voltages at every node, losses, and loading levels. This is what makes GC0139 different from LTDS.

How LTDS and GC0139 data flows connect

The whole-system picture

LTDS and GC0139 are not standalone reforms. They are building blocks in a larger data architecture that connects a connection applicant checking local capacity all the way through to national strategic energy planning. This diagram shows the end-to-end flow of data from a connection application through to the Strategic Spatial Energy Plan, and how the outputs feed back into DNO investment decisions.

What the Engagement Hub provides

All Stage 1.3 artefacts (RDFS profiles, SHACL constraints, modelling guidelines, data exchange specs), release notes, applicability matrices, and a structured forum for technical queries and change requests. It is managed by BSI under Ofgem's governance framework.

Who should be using it

DNO data teams preparing CIM submissions, connection developers building automated screening tools, flexibility market operators, energy system modellers, academic researchers, and anyone working with GB distribution network data. Registration is open via the BSI platform.

Methodology and sources

This page draws on the following regulatory and technical sources:

Regulatory instruments: Standard Licence Condition 25 (SLC25) of the Electricity Distribution Licence (original Aug 2002, Direction 13 Sep 2011). LTDS Direction issued 25 Nov 2024, requiring grid model data using CIM and capacity heatmaps. CIM regulatory approach letter published 10 Jan 2022 confirming CGMES v3 with GB extensions. Consultation on new Form of Statement published 29 Aug 2023.

Technical standards: IEC 61970 (Energy Management System Application Program Interface) and IEC 61968 (Application Integration at Electric Utilities) for CIM. ENTSO-E Common Grid Model Exchange Specification (CGMES) v3. W3C Shapes Constraint Language (SHACL) for validation. W3C RDF Schema (RDFS) for profile definitions.

Stage 1.3 artefacts (November 2025): Grid Modelling Guidelines v5, Data Exchange Specifications v5, CIM100v111 UK LTDS AllProfiles v8, Information Model Extension Definitions v3, LTDS Profiles in RDFS (7 profiles), Constraints in SHACL (EQ Edition 6), Constraints Descriptions v4, Publication Notes v1, Artefact Applicability v1. All hosted on BSI Engagement Hub: cim.bsigroup.com/releases/ltds/november-2025/

GC0139 sources: NESO GC0139 modification page. GC0139 Workgroup Report, 3 December 2025. GC0139 Final Modification Report, 10 March 2026. Ofgem CIM Regulatory Approach Letter, 10 January 2022. Grid Code Review Panel Headline Report, 11 December 2025.

Industry governance: ENA Data and Digitalisation Steering Group (DDSG). BSI governance framework for GB CIM artefact management. Industry working group on LTDS reform (convened Aug 2021). GC0139 requires establishment of a CIM interface point agreement system and a CIM governance body for GB.

DNO compliance status: Based on published LTDS datasets and ENA DDSG progress reports as of March 2026. Coverage percentages are illustrative and based on publicly available information about CIM adoption progress. Mock validation data is synthetic but modelled on the CIM class and property structures defined in the Stage 1.3 RDFS profiles.