Reference
Transformer and switchgear standards, and what each one governs
A distribution project answers to several documents at once. The usual error is the right standard applied to the wrong object.
The equipment you buy, the installation you build around it and the connection to the network are each governed by different documents. A specification that quotes the installation standard to a manufacturer of type tested equipment asks for evidence that standard was never written to produce.
Every scope in these tables was read from the publisher's own catalogue record. The standards themselves are copyright and are sold by their publishers.
Transformers
| Standard | Title | Scope as published |
|---|---|---|
| IEC 60076-1:2011 | Power transformers, Part 1: General | Three phase and single phase power transformers, including auto transformers, except certain small and special transformers |
| IEC 60076-11:2018 | Power transformers, Part 11: Dry type transformers | Dry type power transformers with highest voltage for equipment up to 72.5 kV and at least one winding above 1.1 kV |
| IEC 60076-7:2018 | Power transformers, Part 7: Loading guide for mineral oil immersed power transformers | Loading of mineral oil immersed transformers |
| IEEE C57.12.00-2021 | General requirements for liquid immersed distribution, power and regulating transformers | Electrical and mechanical requirements for liquid immersed transformers |
| IEEE C57.12.01-2020 | General requirements for dry type distribution and power transformers | Ventilated, non ventilated and sealed dry type transformers |
| IEEE C57.12.34-2022 | Pad mounted, compartmental type, self cooled, three phase distribution transformers | 10 MVA and smaller, high voltage 34.5 kV and below, low voltage 15 kV and below |
| EN 50708-1-1 and EN 50708-2-1 | Additional European requirements for power transformers and medium power transformers | Replaced EN 50588-1:2017, which was withdrawn on 28 May 2020 |
A specification that still cites EN 50588-1 cites a withdrawn standard.
Switchgear and substations
| Standard | Title | Scope as published |
|---|---|---|
| IEC 62271-1 | Common specifications for alternating current switchgear and controlgear | AC switchgear and controlgear above 1000 V, service frequencies up to 60 Hz |
| IEC 62271-100 | Alternating current circuit breakers | Three phase AC circuit breakers on systems above 1000 V |
| IEC 62271-200 | AC metal enclosed switchgear and controlgear above 1 kV up to and including 52 kV | Prefabricated metal enclosed assemblies, indoor and outdoor |
| IEC 62271-202:2022 | AC prefabricated substations above 1 kV up to and including 52 kV | Service conditions, ratings, structure and tests of prefabricated substations, operated from inside or outside |
| IEC 61439-1:2020 | Low voltage switchgear and controlgear assemblies, Part 1: General rules | Definitions, service conditions, construction and verification of low voltage assemblies |
| IEC 61439-2:2020 | Power switchgear and controlgear assemblies | Rated voltage up to 1000 V AC or 1500 V DC |
| IEC 60947-2:2024 | Low voltage switchgear and controlgear, Part 2: Circuit breakers | Circuit breakers on circuits up to 1000 V AC or 1500 V DC |
Protection, enclosures, voltages and installation
| Standard | Title | Scope as published |
|---|---|---|
| IEC 60255-1:2022 | Measuring relays and protection equipment, Part 1: Common requirements | Common rules for measuring relays and protection equipment |
| IEC 60529 | Degrees of protection provided by enclosures, the IP code | Classification of the protection enclosures provide |
| IEC 60038 | IEC standard voltages | Preferred nominal voltages of supply systems, including 230/400 V and 11 kV |
| IEC 61936-1:2021 | Power installations exceeding 1 kV AC and 1.5 kV DC, Part 1: AC | Design and erection of installations above 1 kV AC. It does not cover the design of prefabricated, type tested switchgear or prefabricated substations |
Equipment standard or installation standard
IEC 61936-1 governs the design and erection of the installation as a whole. Its own scope excludes the design of prefabricated, type tested switchgear and prefabricated substations, because separate standards exist for them. The station you buy is proven by its manufacturer to IEC 62271-202, and the installation you build around it is designed to IEC 61936-1.
UK network documents and regulations
| Document | What it governs |
|---|---|
| ENA TS 35-1, Issue 8 (2026) | Distribution transformers for UK network operators: two winding, liquid immersed, naturally cooled, 25 to 2000 kVA, at 7.2, 12, 24 and 36 kV |
| ENA TS 41-41, Issue 2 (2026) | Ground mounted distribution substation RMUs and extensible switchgear rated 12 to 24 kV, for 11 and 20 kV systems; replaces TS 41-36 for this equipment |
| ENA TS 41-36, Issue 3 (2012) | Switchgear for service up to 36 kV, cable and overhead conductor connected |
| ENA EREC S40, Issue 2 (2026) | Prefabricated substations, with switchgear up to 36 kV and transformers up to 2000 kVA |
| ENA EREC G99, Issue 2 (2025) | Connection of generation to GB distribution networks, including the operating modes of standby sets |
| ESQCR 2002 | Substation security, notices and fire precautions (regulation 11) and the declared supply voltages and frequency (regulation 27) |
Titles and issues read from the Energy Networks Association catalogue and legislation.gov.uk on 2 October 2026. ENA documents are written for the GB distribution network operators; a customer owned installation uses them where its specification adopts them.
EU regulation
| Regulation | What it governs |
|---|---|
| (EU) No 548/2014, as amended by (EU) 2019/1783 | Maximum losses and minimum efficiency for power transformers placed on the market, still applied in Great Britain |
| (EU) 2024/573 | Fluorinated gases, including the prohibition on putting into operation new medium voltage distribution switchgear with fluorinated gas, up to 24 kV from 1 January 2026 and above 24 kV up to 52 kV from 1 January 2030 |
Sources
| Record | Where it was read |
|---|---|
| IEC standards | IEC webstore publication records |
| IEEE standards | IEEE Standards Association standard pages |
| EN 50588-1 and EN 50708 | BSI Knowledge and NBS records |
| EU regulations | EUR-Lex, and legislation.gov.uk for the GB position |
Verified on 16 September 2026. Standards are revised, so check any row that matters to a decision against the current edition.
How to cite
- Cite as
Daverlan Power Systems (2026). Transformer and switchgear standards, and what each one governs. https://daverlan.com/technical-resources/standards/
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