Do you supply products into Europe? If you supply products that come within the scope of the EMC Directive 2004/108/EC, the application of harmonized standards provides the simplest means of demonstrating conformity with the protection requirements (emission and immunity) of the Directive.
This article will provide you with essential information on the selection and use of the appropriate standards for your product.
How do standards and directives interact?
Directives such as the EMC Directive are so called “new approach” directives. These were introduced from 1985 onwards as a means of speeding up the creation of technical requirements that could be applied throughout Europe. Before that date the regulations contained all the technical requirements for products within their scope. Agreeing on these requirements was a lengthy process, and the legislation was inflexible, incapable of responding quickly enough to technical innovation.
New approach directives set out only the essential requirements in general terms; the technical requirements are contained in harmonized standards that underpin them. However, an important feature of new approach directives is that the use of harmonized standards is always voluntary. The manufacturer can demonstrate conformity with the essential requirements by other means provided that they justify their approach in technical documentation that shows the technical analysis that they have followed.
Most manufacturers apply the requirements of the harmonized standards because they define the technical requirements clearly and are the equivalent of carrying out the electromagnetic compatibility assessment required by the EMC Directive. They also have the advantage that compliance in full with the requirements of all the relevant harmonized standards provides a “presumption of conformity” with the essential requirements of the directive. This means that the market surveillance authorities must presume that a product that is stated to meet the requirements of the harmonized standards meets the technical requirements of the directive, and they cannot remove products from the market unless they can demonstrate that a product does not comply. Where the harmonized standards have not been applied in full, this presumption does not exist.
What is a harmonized standard?
Europe has a series of standards prefixed “EN” – European Norm. These are written by the European Committee for Standardization (CEN), the European Committee for Electrotechnical Standardization (CENELEC), and the European Telecommunications Standards Institute (ETSI). The vast majority of ENs that are relevant for the EMC Directive are produced by CENELEC.
Harmonized standards are ENs produced by CEN, CENELEC or ETSI, following a mandate issued by the European Commission, for use with one or more directives. The lists of harmonized standards suitable for each Directive are published from time to time in an official publication called the Official Journal of the European Union, often referred to as “the Official Journal” or “the OJ”.
This article will describe the application of the standards produced by CENELEC to products in order to meet the requirements of the EMC Directive. The principles for the standards produced by CEN are similar. ETSI standards are produced entirely in Europe and do not have international equivalents.
Why doesn’t Europe use international standards published by IEC?
The majority of ENs are not written exclusively in Europe, but are based on international standards; in many cases the technical content is identical. In the case of CENELEC in 2008, 78.1% of standards published were identical to IEC standards (including CISPR) and a further 4.5% were based on IEC standards (including CISPR), with some modification for European requirements.
An agreement between CENELEC and IEC ensures that any new standardization work required to be produced by CENELEC is first of all offered to IEC, to allow an international version to be produced. CENELEC then takes the text of the international standard in order to produce the EN. Only if IEC rejects the offer, or cannot complete the work to required deadlines, does CENELEC work on the production of the standard.
European legislation is constructed in a manner that requires harmonized standards setting out the technical requirements of a directive to be voted on as European standards. As a consequence, international standards are subject to two votes in Europe, once as the international standard and once as the EN. If both votes are positive, two versions of the same standard are published, the IEC and the EN.
If the international vote is positive, but the voting in Europe shows that there is insufficient support for publication as an EN, then changes are made to the requirements in the EN until a positive vote is achieved. These differences are called “common modifications”. Common modifications may consist of addition of, deletion of, or changes to requirements or test methods.
Another reason why the EN version is published is that IEC standards are recommendations that come into effect immediately; the superseded standard is withdrawn when the new version is published. If this were to have the legal status of a harmonized standard, the change in requirements would be too abrupt to allow industry time to adapt their products to the new requirements. The European versions have a (usually) three year transition period from the date the standard is ratified to the date that the superseded standard is withdrawn. This period applies to all types of standards, and the date of withdrawal of the superseded standard is published inside the front cover of the EN standard. In the case of harmonized standards listed in the Official Journal, the date published in each list in the OJ becomes the relevant date in respect of the application of the standard under that particular directive (see below).
Types of Standards
EMC standards are of several different types: product, product family, generic and basic. Product and product family standards define the requirements and test methods for a small range of products. Generic standards define the requirements and test methods for those product types that are not covered by the more specific product and product family standards. Generic standards are based on types of environment rather than product categories. Finally, basic standards set out test methods or provide guidance and background information. They may contain recommendations but do not set absolute requirements. Consequently, basic standards do not of themselves provide a presumption of conformity. Rather they provide standardized test methods that can be referenced from the other standard types.
How to Select Harmonized Standards – The List in the Official Journal of the European Union
The latest list of harmonized standards that provide a presumption of conformity under the EMC Directive (at the time of writing this article) is available in PDF format, although there has been a change in the date in respect of the 1998 edition of EN 55022.
It will be seen that there are four columns in the table, and that there is an entry for each standard, with any amendments being identified separately. The first column identifies the standardization body that publishes the standard. The second column provides the number and title of the standard. Where the standard is based on an international standard the number is shown in brackets below the title. Where the EN contains common modifications, “modified” is shown.
The third and fourth columns deal with the editions of the standards and amendments that provide a presumption of conformity. For each standard or amendment, the third column lists the standard that is superseded by that standard or amendment. Often, in the case of a new edition of the standard, the superseded standard is the previous edition of the standard and any amendments to it, but it can be the relevant generic standards where a new standard is published that covers products that were not previously within the scope of a product or product family standard.
Amendments are dealt with separately, so for example the superseded standard in the case of an amendment 2 is the standard with its amendment 1. Amendment 2 of the standard has to be applied with effect from the date given for the presumption of conformity to be valid.
The fourth column, entitled “date of cessation of presumption of conformity of the superseded standard” provides the relevant dates. The date is chosen by the Commission; it is generally the same as the date associated with the three year transition period set by CENELEC, but is some exceptional cases it is different. The date listed in this column is definitive in respect of the legal position on whether the correct edition of a standard has been selected. In cases where the date of cessation is earlier than the date that the list was published, it is shown as “date expired” and the relevant date is shown in brackets.
Notes to the list explain the requirements in particular circumstances and in contrast to notes in standards, these notes have legislative effect.
Determining Which Standards Are Relevant
The selected harmonized standards should make a complete provision for emissions and immunity, at both high and low frequencies. In selecting standards from the list in the OJ, the manufacturer should be aware that more specific standards take precedence over more general standards and that the harmonics and flicker standards, EN 61000-3-2 and EN 61000-3-3 respectively, apply to all products intended for connection to the public low-voltage mains electricity supply.
An important principle is that the intended function and use of the equipment determines the standard(s) that should be applied, not the technology employed. Therefore, although a washing machine may contain a microprocessor for controlling its operation, it remains a domestic appliance, and is therefore within the scope of the standards EN 55014-1 and EN 55014-2, and not EN 55022 and EN 55024.
In general, the scopes of the product standards are mutually exclusive. However convergence of functionality is creating products for which requirements are not complete within existing standards. New standards such as CISPR 32 and CISPR 35 are being developed for emissions and immunity, respectively, of multimedia equipment, and these will be harmonized in Europe as EN 55032 and EN 55035. Until such time as more comprehensive standards are available, it may be necessary to apply the parts of more than one standard for each aspect. For example, a computer with a broadcast television reception function will come within the scope of EN 55022 and EN 55024 as an information technology product, but parts of EN 55013 and EN 55020 will need to be applied in respect of the broadcast reception functions, in order to make a complete assessment of the EMC performance for all aspects of the equipment. This still represents a simpler approach for the manufacturer than carrying out an electromagnetic compatibility assessment of the product in accordance with Annex II, point 2 of the EMC Directive.
Although the titles of harmonized standards can be a useful indication of appropriate standards, it is often necessary to examine the scope and even the content of a standard to check its applicability to a particular product. For example, the harmonized standard EN 55014-1 is entitled Electromagnetic compatibility – Requirements for household appliances, electric tools and similar apparatus yet within its scope are the following (non exhaustive list): Cine projectors, automatic dispensing (vending) machines, juke boxes, pinball machines, gaming machines with a winnings-payout mechanism, electric fences, cow milking machines, and air conditioners.
The complete list should be examined in its entirety for more specific standards that would take precedence. For example, EN 55022 and EN 55024 apply to information technology equipment, a subset of which is telecommunications equipment. However these standards are not those that should be applied to network telecommunications equipment because the OJ list contains a more specific standard, EN 300 386 produced by ETSI that has the scope of telecommunications network equipment.
Which editions of the standards can/must be used?
In the case of EMC harmonized standards listed in the Official Journal, the standard provides a presumption of conformity with the relevant essential requirements as soon as it is included in the list, and published by at least one national standards body. This may be some months after the standard is actually published by national standards bodies. During the period up to the date of cessation of presumption of conformity of the superseded standard, both the new and superseded editions provide a presumption of conformity. The superseded standard ceases to provide this presumption on the date given, so manufacturers using the standard should update their declarations of conformity accordingly, having first satisfied themselves that their product complies with the requirements of the new edition.
Many harmonized standards refer to basic standards for test methods, and these references may be dated or undated. In the case of dated references the specific edition of the referenced standard, including any amendments specified, must be used, even if a later edition of that standard has been published. With undated references, the latest edition of the referenced standard must be used, although the previous edition may be used up to its date of withdrawal. A dated reference provides more certainty for the manufacturer, and the majority of new EMC standards being produced by the main EMC committees are now adopting dated references. This may not be the case, however, for standards that contain EMC requirements along with other requirements that are produced by the product standards committees.
A special case occurs where the referenced standard is itself a harmonized standard listed in the Official Journal. This can occur where for historical reasons a product family standard defines test methods within the body of the standard because suitable basic standards were not available at the time that the first edition of the product family standard was written. Another harmonized standard then makes reference to the product family standard.
The principle to be followed in this case, where the reference is dated, is that the standard for the product in question is the primary requirement, and that the edition of the referenced standard that is to be used is the one determined by the product standard. Thus, the dated reference is followed, irrespective of whether that edition is listed in the currently valid list in the Official Journal.
What is Annex ZA in the European standards?
When an international standard is ratified by CENELEC as an EN, the national standards bodies that publish the standard take the entire international text (subject to any common modifications that have been necessary). This means that throughout the text, references to other standards will be to their international versions. For Europe, it is the EN versions of these standards that are the relevant references, and Annex ZA has been developed to deal with this. It is so designated to ensure that it comes after the normative and informative annexes of the international text.
Annex ZA consists of five columns. The first two provide the number and date of the international version of the standard as referenced in the international body text of the standard. The third column provides the title of the referenced document. The third and fourth columns provide the number and date of the corresponding European version of the referenced standard that must be used for the correct application of the standard. Where no equivalent is published a dash appears in the right hand columns, and the internal version must be used.
If a year is not given in the fifth column, the reference is undated. It is possible for the international version to be an undated reference and for the EN reference to be dated.
It is recognized that the wording of Annexes ZA as currently provided is not entirely clear, and work is in hand in Europe to improve this situation.
The informative Annex ZZ in harmonized standards is a relatively recent innovation that is being introduced as standards are amended or new editions are published. It seeks to provide guidance to users of the standards on the coverage in the standard of essential requirements under various directives. It should be used with care, because it does not indicate whether the standard makes a complete provision in respect of the essential requirements that it identifies, or whether other standards must be applied in addition. For example, EN 55022 contains an Annex ZZ that indicates that it covers EMC emission aspects for the EMC Directive 2004/108/EC and the R&TTE Directive 1999/5/EC. However it does not indicate that the harmonics and flicker standards are applicable, in addition, for equipment within its scope that is connected to the public low-voltage electricity supply.
In some cases, a requirement in a standard is found to be unclear or ambiguous, yet the problem is not sufficient to warrant an immediate amendment to the standard. Such cases are dealt with by an Interpretation Sheet. These are a relatively new development, and may be published to clarify a requirement in a standard, but not to modify it; such changes would be the subject of an amendment.
In the British Standard version of ENs, Interpretation Sheets are included as amendments to the standard, but this is not the case for all national implementations of ENs. The existence of interpretation sheets may be checked in the online catalogue on the CENELEC website www.cenelec.eu, where putting the number of the standard (without “EN”) in the search box on the top right hand side of the home page will produce a list of current and draft documents associated with that standard.
In respect of the application of a standard and the presumption of conformity under a directive, Interpretation Sheets are guidance, and therefore such documents referring to harmonized standards are not listed in the Official Journal. The presumption of conformity is not affected if they are not followed, but since they represent the official opinion of the responsible standards committees, it would be prudent to follow the interpretation.
Alternative Test Methods
Many harmonized EMC standards offer alternative test methods for demonstration with the requirements. The question has arisen in recent years as to how these should be considered, especially if a challenge is made by market surveillance authorities to a declaration of conformity under the EMC Directive that is supported by compliance with such standards.
The subject has proved to be controversial, but the interpretation in Europe is clear, resulting in a statement in the European Commission’s Guide for the EMC Directive 200/108/EC. This states “alternative test and measurement methods, when introduced into a harmonized standard for the same purpose are considered, together with their associated limits, as equivalent regarding the provision of a presumption of conformity with the protection requirements”.
European standards are being checked for consistency with this position, and in some cases this results in a change (by common modification) from the international equivalent. The wording in EN 55022:2006 dealing with this issue reads as follows: “Where alternative test methods are described in the following subclauses, compliance with the requirements of the subclause may be demonstrated by either or any of the methods described.”
Documents Providing Further Guidance
CENELEC has produced Guides 24 and 25 to provide explanations of the use of harmonized standards for EMC. They may be downloaded free of charge.
Guide 25 Guide on the use of standards for the implementation of the EMC Directive will be the most useful for manufacturers, although Guide 24 EMC standardization for product committees also provides useful background information.
The third editions of these guides are about to be published, and may be available by the time this article appears in print. These update the references to the new EMC Directive 2004/108/EC and to other documents.
Brian Jones is an independent EMC Consultant, specializing in compliance with European legislation and standards. He is also secretary to the CENELEC EMC committee TC210, but is writing here in a personal capacity, and his views do not necessarily reflect the views of any organization. He may be contacted at emc @brianjones.co.uk.