EMC Good Practice Makes Perfect

22 Apr 2021

EMC Good Practice Makes Perfect

In the European Union, the EMC Directive requires all “fixed installations” to employ “good EMC engineering practices”, as do all national electrical codes (BS 7671, the IET Wiring Regulations, in the UK), and EN 62305 requires the use of good EMC engineering to protect all equipment on sites against damage from lightning. If non-compliance is discovered, site insurance could be problematic.

Keith Armstrong from EMC Standards explains what all this actually means.

EMI Stories has over 800 examples of real-life EMI incidents, which range between hilarious and frightening, and are only the tip of the EMI iceberg. EMC is the discipline of preventing undesirable EMI by both limiting electromagnetic emissions and ensuring adequate immunity to electromagnetic phenomena.

A “fixed installation” can be a commercial or industrial site; a national infrastructure such as electrical, telephone, internet, road or rail networks; or a system within a building, such as a lighting system, computer network, HVAC system, production line, etc.

The EMC Directive requires the owners or operators of each fixed installation to appoint a “Responsible Person” to oversee its EMC compliance. Some sites might have a single person responsible for everything; others might have several people each responsible for different fixed installations.

Each responsible person must ensure their fixed installation does not interfere with radio, telecommunications and other equipment, and operates as intended despite the EMI in its operational environment. They must also ensure that good EMC engineering practices are used, and apply the EMC installation/use instructions provided with supplied equipment. These activities must be documented, and the documents kept ready for inspection by national EMC authorities for the operational life of the fixed installation.

EMC enforcement agents have the authority to immediately close down fixed installations that they think cause EMI problems, and have done so after receiving complaints of EMI.

M&E contractors and installers may see good EMC engineering requirements in their contracts, but need to understand that the EMC Directive only applies to a fixed installation’s owners or operators. So, for example, a specification: “The work must comply with the EMC Directive” is meaningless because no contract can make a law apply to someone not covered by that law.

A specification that states: “Good EMC engineering practices must be used” is also meaningless, because the good EMC practices required depend on a site’s electromagnetic environment, and how the responsible person wishes to control EMI issues.

A problem with the EMC Directive, national electrical codes, and EN 62305 is that they do not describe all the practical good EMC engineering details that are needed. So, any specification for subcontract work should specify exactly the good EMC engineering practices required, in practical detail, plus exactly what verification or validation procedures are required (e.g. inspections; in-situ EMC testing, etc.).

For example, many mistakenly believe that good EMC engineering requires the use of single-point (‘star’) earthing/grounding systems; terminating cable screens at only one end; and connecting filters and cable screens to earth/ground using any length green/yellow insulated wire. But these techniques are decades out of date and are now bad EMC practices in general, and recognised as such in relevant standards.

There is also the mistaken idea that constructing systems and installations from CE-marked equipment and following their suppliers’ instructions is all one has to do for EMC – the so-called “CE + CE = CE approach” – but this has no technical or legal basis. Another mistaken belief is that complying with the EMC Directive also takes care of functional safety risks caused by EMI – which it does not.

There is no escaping the fact that we all need to learn and apply good EMC engineering practices. EMCstandards makes all the necessary information available for free and has books and up-to-date training course notes at reasonable prices.

I am also hosting some on-demand training in May 2021 on the following subjects:-

• Why “CE+CE=CE” cannot be relied upon for EMC compliance
• Low-cost, quick, benchtop EMC testing helps de-risk all project stages
• How to achieve EMC Compliance under the RED
• Practical Electronic Design Techniques for Cost-Effective SI, PI and EMC in 2021  

Please visit EMCUK  to register!

Photo by Brett Jordan on Unsplash

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