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The Energy Networks Association (ENA) represents the interests of all electricity network operators in the UK. The Document Catalogue System is an online catalogue of engineering and Safety Health and Environment (SHE) documents available from the ENA. The engineering documents that you can access from the site are:Engineering Recommendations (EREC)Engineering Reports (EREP)Technical Specifications (TS)ACE ReportsEngineering Technical ReportsEngineering Equipment Assessment Lists
The Safety Health and Environment (SHE) documents that you can access from the site are:SHE StandardsSHE Position PapersSHE Briefings
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WARNING! Some of the older (pre 2003) documents available on this site were originally published by the now defunct Electricity Association. Please note that the ENA cannot take responsibility for the condition and content of these older documents and you are advised to seek advice before acting upon information held in them.
Information Exchange between Distribution Network Operators
Connections in Constrained Areas: Technical Guidance on the Options for Managing Curtailment at the Boundary between Network Operators
Live Tank Circuit Breakers to use on 400 kV Transmission System
Guide to the Application of Engineering Recommendation P28 Issue 2
Functional Test Requirements – Transformer Differential Protection
Functional Test Requirements – Voltage Protection
Protection of telecommunication lines from power lines
Engineering Technical Report 132 Issue 3 2025 Improving resilience of overhead networks under storm conditions.
Application Guide for Wildlife Protection Schemes for HV Overhead Lines
Reporting of incidents to the Health and Safety Executive (HSE) in accordance with regulation 31 of the Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR)
Functional Test Requirements – Busbar Protection Relays
Managing the Risks Associated with the Provision of Multiple Connections in Close Proximity
Standard Application Form - Connection of Power Generating Modules to DNO Distribution Networks in accordance with EREC G99
Wildlife Protection Product Specification for HV Overhead Lines
Safe Working on the Low Voltage Electrical Distribution System
Power Quality Information Required for Heat Pumps and their Assessment
Working in or Near Water (including Flood Water)
Voltage Measurements for Assessment of Compliance with Statutory Voltage Limits
Instructions for Reporting to the National Fault and Interruption Reporting Scheme
Guide to the practical aspects of quality management associated with assessment of power system plant & products
Guide to the assessment of power system products for use by the ENA Member Companies
Part 2D: Procedure for the conformity assessment of protection products
Requirements for the connection of Fully Type Tested Micro-generators (up to and including 16 A per phase) in parallel with public Low Voltage Distribution Networks on or after 27 April 2019
EREC G98 Application Forms
Distributed Generation Connection Guide: G98 & G99
Requirements for the connection of generation equipment in parallel with public distribution networks on or after 27 April 2019
EREC G99 Application Forms
Separation between Wind Turbines and Overhead Lines: Principles of Good Practice
Code of practice for overhead to underground optical cable connections
Code of practice for the installation of ADSS optical cable
Post Trip Manual Reclosing of High Voltage Electrical Distribution Circuits
Distribution Network Operator Response to Reports of Low or Grounded Overhead Lines
Testing approach for merging units for protection sampling of instrument transformers in accordance with BS EN IEC 61869-13
Telecommunication Providers and Distribution Network Operators joint use of poles
Design and use of temporary scaffold guards and conductor support systems
Distribution cables of rated voltage 0.6/1/ (1.2) kV with XLPE insulation, concentric waveform copper wire and solid aluminium conductors
Environmental test requirements for protection and control equipment and systems
Guidelines for the Provision of Low Voltage Connections to Multiple Occupancy Buildings
Switchgear for use on 66 kV to 132 kV distribution systems Part 5 Inductive voltage transformers, capacitor voltage transformers, combined unit transformers and current transformers for use on 72.5 kV to 145 kV distribution systems
Power installations exceeding 1 kV a.c. – Design of high-voltage open-terminal stations
Aerial bundled conductors insulated with cross-linked polyethylene for low voltage overhead distribution
Specification for single circuit overhead lines of compact covered construction on wood poles for use at high voltage up to and including 33 kV
XLPE covered-conductors for overhead lines (having rated voltages Uo/U greater than 0.6/1 kV up to and including 19/33 kV)
Single core cables for use in substations having extruded insulation and rated voltages of 6350/11 000 volts, and 19 000/33 000 volts
Environmental classification and corrosion protection of structures, plant and equipment
Fittings for covered conductors for overhead lines (having rated voltages U0/U greater than 0.6/1 kV up to and including 19/33 kV)
Portable earthing equipment for overhead lines and substations
Complexity of Distribution Circuits Operated at or above 22kV
Stay strands and stay fittings for overhead lines
Guide to the application of Engineering Recommendation G5/4 in the assessment of harmonic voltage distortion and connection of non-linear equipment to the electricity supply system in the U.K
Calculation of fault currents in three-phase AC power systems (Application Guide to Engineering Recommendation G74)
Issue 3 - Amendment 8
Recommendations for the Connection of Generating Plant to the Distribution Systems of Licensed Distribution Network Operators
Engineering Recommendation G99/NI Issue 1 – Amendment 1 7 December 2023 Requirements for the connection of generation equipment in parallel with public distribution networks in Northern Ireland on or after 27 April 2019
Guidance on the application of Engineering Recommendation P2, Security of Supply
Security of Supply
Requirements for the Application of Protective Multiple Earthing to Low Voltage Networks
Analysis package for assessing the security contribution from distributed generation and electricity storage systems – Users’ guide
Analysis Package For Assessing Generation Security Capability - Users' Guide
Harmonic voltage distortion and the connection of harmonic sources and/or resonant plant to transmission systems and distribution networks in the United Kingdom
AC traction supplies to British Rail
Issue 2 Amendment 3 Recommendations for the Connection of Type Tested Small-scale Embedded Generators (Up to 16A per Phase) in Parallel with Low-Voltage Distribution Systems
Issue 1 Amendment 4 Requirements for the connection of generation equipment in parallel with public distribution networks on or after 27 April 2019
Voltage fluctuations and the connection of disturbing equipment to transmission systems and distribution networks in the United Kingdom
Guidelines for the design, installation, testing and maintenance of main earthing systems in substations
A guide for assessing the rise of earth potential at electrical installations
Framework for new low voltage housing development installations - Part 1 Design and planning
Framework for new low voltage housing development installations - Part 2 Materials specification
Framework for new low voltage housing development installations - Part 3 Installation and records
Framework for new industrial and commercial underground connections - Part 4 Design and planning
Framework for new industrial and commercial underground connections - Part 5 Materials specification
Framework for new industrial and commercial underground connections - Part 6 Installation and records
Framework for contestable diversionary and reinforcement works not exceeding 33 kV - Part 7 Contestable diversionary and reinforcement works
Use of Mechanical Harvesters in Vegetation Management
This document aims to give guidance on work using mechanical harvesting methods within 120 the Red Zone of live overhead power lines that is either instigated by the Network Operator 121 (for enhanced network security for example) or by a Third Party (usually commercial 122 harvesting). In either case these recommendations shall only be used where the work is 123 managed by the Network Operator. In this respect the Network Operator will assume the role 124 of Forestry Work Manager as defined in the FISA booklet, Guidance and Managing Health 125 and Safety in Forestry [N7]. The Network Operator then accepts responsibility for the 126 following tasks in respect of the work: 127 • Use information provided by the Landowner to prepare a risk assessment 128 • Select competent staff or contractors who have made adequate provision for health and 129 safety 130 • Make the machine and system choice 131 • Specify the health and safety measures for staff or contractors working on the site and 132 others who may be affected by the work activity 133 • Liaise with the Landowner 134 • Monitor health, safety and network security using a Network Operator Site Supervisor 135 who will be permanently on the site during work 136 It is recognised that when the Network Operator accepts the role of Forestry Work Manager 137 there will be instances where the work is happening concurrently with other work activities. In 138 these cases provision must be made to ensure that the safety and contractual responsibilities 139 of all parties are clear throughout the operations. Thorough consultation at the planning 140 stage between the Network Operator and the Landowner is essential. This document does 141 not seek to detail the variety of responsibilities that may need to be allocated nor does it seek 142 to give guidance on the collaborative process required to achieve this.
Medium revision to incorporate into the latest ENA template and review and capture any impact from changes in technology and tree harvesting machinery available. This issue includes the following principal technical changes.. Clause 7.3, bullet point 10: The requirement that there be no possibility of a machine being positioned such that it could breach the Vicinity Zone is relaxed to allow such positioning in exceptional circumstances. Guidance added on appropriate control measures to be put in place in such circumstances. Annex B, Hazard 2: Requirement that any operations requiring the machine to be positioned where it could breach the Vicinity Zone can only be done under the supervision of an SAP amended to allow this to be done alternatively by an appropriate Manager approved by the Network Operator.
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