Special National Conditions (SNC)


1.1 As each CENELEC member has the obligation to implement every EN by giving it the status of a national standard and withdrawing any conflicting national standard(s), if a CENELEC member is confronted with a situation where it has to implement an EN or an HD  that is not compliant with a specific, unchangeable condition in its country, it is their right to ask for a “Special National Condition” to clarify or modify a specific provision according to the national conditions.

1.2 A Special National Condition (SNC) is defined as a “national characteristic or practice that cannot be changed even over a long period, e.g. climatic conditions, electrical earthing conditions”. In practice, this means that an annex needs to be written that gives information to the standard user on how that standard has to be applied within a particular national territory.

1.3 SNCs do not release CENELEC members from their obligation to implement the relevant EN or HD.

NOTE: SNCs differ from A-deviations, which are developed because a standard would otherwise conflict with a local legal requirement.


2.1 When it is impossible to avoid SNCs, all relevant information concerning them is included in a normative annex to the EN.

2.2 The exceptional aspect of the SNC should be taken into account as soon as possible, normally when a CENELEC member proposes new work and/or when a CENELEC technical body drafts an EN.

2.3 SNCs only apply to the normative provisions of an EN or HD. An SNC may also apply to all the requirements of the EN or HD.
Normative provisions of European Standards are called requirements. They are introduced by the modal verb "shall" or the use of the infinitive form.

2.4 CENELEC publishes documents other than EN and HD, for instance Workshop Agreements (CWA), Technical Specifications (TS) or Technical Reports (TR) that can be adopted as national deliverables; there is no systematic implementation of such documents, hence a difference due to national conditions should not be a problem.


3.1 Risks of conflicts between national conditions and a future EN or HD should be identified as early as possible, preferably when a new subject of work is proposed. An early notification would allow the technical body to adapt its draft in order to avoid the request for an SNC. Where it is not possible to adapt the draft, CENELEC members should inform the relevant technical body of their need to request (or maintain during revision) an SNC as soon as the drafting starts and at the latest during the Enquiry.
Any late notification of the need for an SNC may result in an amendment to the EN or HD as soon as it is published. (see decision D152/C045)

3.2 The request from a CENELEC member for a possible SNC shall contain:

  • a critical examination of the national situation in regard to its national conditions;
  • the work item(s) affected by this request;
  • the clauses of the draft(s) affected by this SNC.

It is the responsibility of the CENELEC Member to verify that SNCs are still relevant and valid when deliverables are reviewed and to inform the technical body accordingly.

3.4 Any technical body, when receiving such a request, should:

    • try to avoid the SNC (e.g. by adapting the draft);
    • verify whether or not the condition is impacting the EN, i.e. whether there is actually a contradiction between the national conditions and requirement(s) in the (pr)EN (or HD).

3.4.1 In case the SNC does not impact the EN, the technical body informs the notifying member about it.

3.4.2 When the SNC is impacting the EN, the technical body should:

  • list the countries having such an SNC, with all relevant information, in an informative annex to the EN;
  • finalize the draft and send it to CCMC (production@cencenelec.eu) in order to start the Enquiry or Formal Vote procedure.

In justified cases, a modification to, or inclusion of, the SNC might be required after the Formal Vote.
Requests for, or modifications to, SNCs made after the standard has been voted upon or published require BT approval (after TC advice) through a consultation by correspondence. The result is published as an Amendment to the standard if the standard has already been ratified. If the standard is not yet ratified, the results are incorporated into the text before publication.


EN 50122-1:2011, “Railway applications – Fixed installations – Electrical safety, earthing and the return circuit – Part 1: Protective provisions against electric shock”, contains SNCs for Denmark, France and the United Kingdom. These are contained in an informative annex.

The SNCs for Denmark and France both relate to Clause 4.1, “Overhead contact line systems” and give the parameters which define the dimensions of the overhead contact line and current collector zones. The text in Clause 4.1 allows for national definitions of these parameters and so no separate justification is necessary.

The SNC for the United Kingdom relates to Clause 5.2.1, and requires different public area clearances from those in the main body of the standard. A clear justification is given: “The revised clearance is due to restricted infrastructure clearances. In order to comply with the public area dimension in Figure 4 it would be necessary to change a large number of civil engineering structures, at a very high cost.”


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