Protecting systems small and big from electromagnetic disturbance

IEC TC work on EMC protects covers multiple domains

By Morand Fachot

Electromagnetic interference can adversely affect many electronic and electrical systems and equipment. Ensuring the electromagnetic compatibility (EMC) of these systems and equipment is essential today.

High-altitude nuclear explosions can have the same destructive impact... IEC SC 77C develops Standards to protect from the effects of high altitude electromagnetic pulse

EMC: what is it all about?

Electromagnetic compatibility (EMC), the ability of electronic and electrical systems or components to work correctly when they are close together, is important in many systems, in particular when it affects their reliability and safety.

EMC implies limits on electromagnetic disturbances emitted by a component or system as well as immunity from this component or system to electromagnetic disturbances from other equipment operating in its proximity.

The disruption created by electromagnetic interference (EMI) may be little more than annoying when it has an impact, for instance, on radio or television reception, but it may be critically important when it affects the safety of systems and users.

International Standards, Technical Reports and Technical Specifications in the field of EMC "with particular emphasis on general application and use by product committees (horizontal function)", are developed by IEC TC 77: Electromagnetic compatibility.

IEC TCs and SCs refer to a number of IEC TC 77 publications, and to IEC Guide 107:2014, Electromagnetic compatibility – Guide to the drafting of electromagnetic compatibility publications, developed by the Advisory Committee on Electromagnetic Compatibility (ACEC), to prepare specific International Standards for their products.

IEC TC 77 was established in February 1981 and held its first meeting in February 1983.

Some 260 experts are currently active in this TC and its three Subcommittees (SCs), each one covering specific areas. 

Low and high frequencies, and high power

IEC SC 77A develops International Standards in the field of EMC with regard to low frequency phenomena, i.e. lower than (or equal to) 9 kHz). Over 150 experts participate in the work of its five Working Groups (WGs) which cover harmonics and other low-frequency disturbances, voltage fluctuations and other low-frequency disturbances, low frequency immunity tests, description of the electromagnetic environment associated with the disturbances present on electricity supply networks, and power quality measurement methods.

IEC SC 77B for its part, develops International Standards "in the field of EMC with regard to high frequency continuous and transient phenomena", i.e. higher than (or equal to) to 9 kHz.

Some 70 experts are active in SC 77B single WG on radiated and conducted continuous phenomena immunity tests, in its Maintenance Team for transient phenomena immunity tests and in its three Joint Task Forces (JTFs) with the IEC International Special Committee on Radio Interference (CISPR).

IEC SC 77C: High power transient phenomena, prepares International Standards in the field of EMC "to protect civilian equipment, systems and installations from threats by man-made high power transient phenomena including the electromagnetic fields produced by nuclear detonations at high altitude (High Altitude Electromagnetic Pulse (HEMP)) and sources of Intentional Electromagnetic Interference (IEMI)." Some 30 experts are involved in SC 77D activities. SC 77D publications number over 20 International Standards, Technical Reports and Technical Specifications. 

Essential work in countless domains

All International Standards and other documents developed by IEC TC 77 and its SCs are essential to reliable and safe operations of countless systems and equipment in many industrial and other domains, such as the medical environment.

In a very specific field IEC SC 77C work is seen as absolutely essential by governments and organizations that seek to protect infrastructures from high power EM threats.

This can be observed in documents and references provided to the UK House of Commons Defence Committee by IEC SC 77C Chairman Radasky and Secretary Dr Richard Hoad. They figure prominently in the Committee's 10th Report of Session 2010–12: "Developing Threats: Electro-Magnetic Pulses (EMP)". In addition, earlier work by the US Congressional EMP Commission included contributions from IEC SC 77C. Their work is published in two reports available at

As regards standardization and other organizations, IEC SC 77C publications have been adapted in recent years to the needs of the telecommunications industry by the International Telecommunication Union (ITU) in ITU T Recommendations K.78, and K.81, and to the needs of the international power industry in the International Council on Large Electric Systems (Cigré) WG C4.206 where work is underway.

EMC test chamber EMC testing chamber for electronic components (Photo: Philips)
High-altitude nuclear explosions test IEC SC 77C develops Standards to protect from the effects of high altitude electromagnetic pulse