The New EMC Directive - Good News for System Integrators?

The New EMC Directive - Good News for System Integrators?

By Ken Webb, TÜV Product Service Ltd
Published: January 2007 - Rail Technologies Magazine

There will no longer be a mandatory requirement for the involvement of a competent third party under the new EMC Directive 2004/108/EC when appropriate harmonised standards are not applied in full. However there will be new mandatory requirements applicable to all manufacturers of equipment within scope, and this article discusses the particular issues faced by system integrators where compliance is based on a combination of in-situ EMC testing and the EMC performance of Commercial Off The Shelf (COTS) apparatus.

What are the Issues?

Change in legislation and requirements
Under the new EMC Directive, the more relaxed compliance r‚gime no longer mandates the involvement of a competent third party (currently a Competent Body, but in future a Notified Body) when appropriate harmonised standards are not applied in full. There will be just one route to compliance, Self Declaration (Internal Production Control), and the involvement of a Notified Body becomes voluntary. While this may be welcomed by many manufacturers and system integrators who currently apply the Technical Construction File (TCF) route to compliance, they should be aware that the new Directive does have some new mandatory requirements applicable to all manufacturers and suppliers whose equipment falls within its scope.

Two key requirements mandated under the Directive involve performing an EMC assessment and the preparation of technical documentation.

Under the existing Directive the only document required under the Self Declaration route is a Declaration of Conformity (DoC). Although EMC Guidelines contain recommendations for other product related information to be produced, the DoC is the only legal requirement apart from a certificated TCF if the manufacturer has followed that route to compliance.

Fig 1: Declaration of Conformity

Under the new Directive there is a legal requirement that technical documentation must be produced enabling the conformity of the apparatus with the essential requirements to be assessed. It must cover the design and manufacture of the apparatus as detailed below:

1. a general description of the apparatus;
2. evidence of compliance with the relevant national standards, if any, applied in full or in part;
3. where the manufacturer has not applied harmonised standards, or has applied them only in part, a description and explanation of the steps taken to meet the essential requirements, including a description of the electromagnetic compatibility assessment, results of design calculations made, examinations carried out, test reports, etc;
4. a statement from the Notified Body, if requested by the manufacturer.

Annex II of the Directive details the conformity assessment procedure and includes a requirement for the manufacturer to perform an EMC assessment of his apparatus. It states that correctly applied relevant harmonised standards or standards which make complete provision in respect of the apparatus, will be equivalent to performing an EMC assessment. However, where the apparatus complies only in part with the relevant harmonised standards or standards, it shall be presumed to comply only with those parts of the essential requirements which correspond to the elements of the relevant harmonised standard or standards with which the apparatus complies.

A typical example where harmonised standards are applied in part only is in-situ testing and a description and explanation of the steps taken to meet the essential requirements, including a description of the EMC assessment will be required. In summary, the EMC assessment shall take into account the following as a minimum:

1. All intended operating conditions of the apparatus
2. Different configurations
3. The relevant phenomena to meet the essential requirements

For systems integrators adopting the TCF route under the current Directive this should be familiar territory. They will know the level of detail and information required by their chosen Competent Body and performing an EMC assessment and preparing technical documentation should not present a problem to them.

However it’s worth reminding ourselves of two key compliance problems faced by system integrators, as they will need careful consideration when deciding how best to satisfy these two new requirements.

The limitations of in-situ EMC testing
Many large systems and items of equipment cannot be tested in a controlled laboratory environment due to their size and/or complexity (for example a complete train or a full flight aircrew training simulator). In such cases testing is performed in-situ either at the manufacturer’s premises or at the final installation site. For a variety of reasons only partial testing can be carried out, and those tests that are performed provide limited data only. Therefore performing EMC testing outside of a controlled laboratory environment invariably results in part application of appropriate harmonised standards and the case for EMC compliance, based on test data obtained in this way, is weakened as a result. Because of the limited EMC test information provided, greater emphasis is placed on the EMC performance of Commercial Off The Shelf (COTS) equipment integrated into the final system.

EMC performance of COTS equipment
Advanced electronic technology is finding applications in many industry sectors and these are commonly supplied as COTS solutions. For example, in order to compete with airlines, Train Operating Companies are looking at a number of ways to improve their service for passengers, including internet access and in-train entertainment systems. This involves the introduction of radio and IT systems onto trains and the rail infrastructure.

This increased use of COTS equipment offers a number of commercial and technical advantages:
1.Readily available, tried and tested technology
2.Relatively cheap compared with bespoke solutions
3.Employs the latest, advanced, technology

However, the advantages gained by using COTS equipment can be significantly reduced in impact if the EMC performance is less than that required by the finished system and this, in turn, results in a requirement for additional documentary evidence, analysis and possibly further testing.

A common problem faced by system integrators is when the COTS equipment is designed to operate in a more benign electromagnetic environment than the final system, and its corresponding EMC performance may be less than that required by the final system. As EMC test standards applied to COTS products may be limited in scope, in terms of frequency range and limits/levels applied during testing, they are more likely to be vulnerable to upset at the higher levels of RF fields and transients experienced in the final system environment. Whilst radiated and conducted emissions from COTS equipment are less of an issue, due to the tighter emission limits imposed on IT, radio and other similar products, the potential to cause interference in co-located systems cannot be ignored, particularly where emissions are in-band of sensitive receiver systems or where COTS radio equipment is installed on a train.

Due to the issues raised above, the level and detail of the EMC documentation supporting the COTS equipment takes on added importance. The system integrator needs to assess whether the shortfall in the EMC performance of the COTS equipment is significant, and whether mitigating measures such as shielding, filtering or special cables are necessary. Typically, this is done via a simple ’gap analysis’, comparing the stated EMC performance of the COTS equipment against the final system EMC requirements. Particular attention is paid to those electromagnetic phenomena that can’t easily be tested during final system in-situ testing, e.g. radiated immunity or surge testing.

Although there is a legal requirement for suppliers of COTS apparatus to raise a valid and current Declaration of Conformity (DoC), as many system integrators have found out, obtaining this document is not always easy. It is not unknown for COTS equipment to be procured with no supporting EMC information or only the minimal information provided in a product specification. Even where DoCs are obtained, performing the gap analysis can still be difficult as many suppliers list only the applicable product specific, product family or generic EMC standards; the basic standard tests are not listed.

There is nothing legally wrong with this approach, but if the ’basic’ standards are not listed this presents the system integrator with a problem; namely which EMC tests have been applied under the listed product or generic standards?

For example EN 55024 specifies 14 individual immunity tests grouped together on a port by port basis. In order to compare the EMC performance of COTS equipment with the intended EM environment of his equipment, the system integrator will need to know which of the 14 tests specified in EN 55024 have been applied. In an ideal world system integrators would have access to their supplier’s EMC test reports, but experience shows that a request such as this is normally given short shrift by COTS equipment suppliers.

In summary, identifying the shortfall in EMC performance between the final system and the supplied COTS equipment is not an easy task on most large projects due to the inadequacies of the supporting documentation. Nevertheless a case for compliance must be prepared and under the current Directive this is described in the technical rationale, or technical argument, of the system integrator’s TCF. Currently, a Competent Body effectively underwrites the system integrator’s case for compliance.

Fig. 2: New EMC Directive requirements bring new responsibilities for manufacturers

Under the new Directive the system integrator is still faced with the problem of compiling a case for compliance based on inadequate documents, but the new regime will allow him to self declare; Notified Body involvement will be voluntary.

What can be Done?
The new Directive places a mandatory requirement on suppliers of apparatus, including systems, to perform an EMC assessment and prepare technical documentation. Two key problem areas for large systems have been outlined above, and this begs the obvious question, what can be done to improve the process?

Firstly, open up lines of communication so that those involved in different projects share information and experience. There is particularly a problem with some large, project-driven companies where project teams work in isolation, with no common practices. If one project team has adopted a rigorous, efficient and successful COTS integration process, other project teams probably won’t know about it.

Secondly, companies can raise awareness of the compliance issues from purchasing onwards and ensure that procedures are in place to assess the information provided by suppliers. Procedures may include, for example, specifying exactly what documentation must be produced - at the very least a DoC plus installation instructions - and ensuring that test standards, levels and limits are in line with the requirements of the final system. NB merely checking that bought-in equipment carries CE marking is not an adequate purchasing procedure!!

In some exceptional cases, system integrators will come to the conclusion that they cannot get adequate information from suppliers, and know they never will, no matter how hard they try. In this case, the standards gap analysis is modified to include a ranking scheme and an assessment of the design of the COTS equipment in terms of its primary function and how well or badly it is engineered and built. The gap analysis may suggest mitigating measures, which can be implemented to achieve a smoother road to compliance. If doubts remain the only option may be to test incoming COTS equipment.

Final Thoughts

It is too early to tell whether system integrators who currently use Competent Bodies for assessing their TCFs will view the relaxation to conformity assessment as an opportunity to go it alone thereby saving money on the Notified Body assessment. Some system integrators, particularly those involved with larger projects, e.g. trains, full flight simulators etc, have indicated that they may continue with an approach similar to the current regime whereby having an independent third party assessment of their technical documentation represents good value for money, particularly in terms of ’risk sharing’.

Obtaining the necessary information and assembling the arguments to fill the identified gaps can be excessively onerous for the system integrator, often under intense pressure to complete the project. Familiarity with standards, and knowledge of EMC measurement and mitigation techniques, do not form part of the system integrator’s core business, and therefore may not be available in-house.

However, those system integrators who wish dispense with an independent assessment of their system need to ensure they have robust processes and procedures in place for performing EMC assessments and compiling technical documentation. Expertise can easily be lost through staff turnover, which is then further compounded by the lack of on-going training. As project timescales get squeezed resource gets diverted onto ’more important’ deliverables and the risk of placing non-compliant systems on the market place can increase.

Clearly there are costs associated with contracting-out the EMC compliance assessment of a project. But for larger projects in particular, they will be a drop in the ocean by comparison with the overall project budget. The benefits, however, are substantial. By separating the compilation of the technical documentation from the main thrust of a project, the provider can focus on the delivery of the project, with the assurance that its EMC compliance will still receive the required specialist attention. As many system integrators have found, forming a partnership with a technically competent and professional notified organisation is a cost-effective way of bringing core competence and experience to a project and, significantly reduces the risk of severe penalties due to delivering a non-compliant system.