Measuring and setting EMC limits

By Philippa Martin-King

CISPR, the international special committee on radio interference, is one of two IEC TCs (Technical Committees) that deals with EMC (electromagnetic compatibility), the other being IEC TC 77: Electromagnetic compatibility. CISPR deals with interference, or rather the unwanted effects of it. In a world of increasing electrification, CISPR is faced with new challenges to ensure that limits are adapted and standardized in line with the technologies being developed. One of the key areas for new EMC work concerns renewable energies, where the flow of energy generated for the grid is often irregular and inconsistent.

The waveform of an AC power circuit is a sine wave.
The waveform of an AC power circuit is a sine wave.

Controlling the noise in an electromagnetic world

CISPR sets the limits for electrical interference that is caused or emitted by all types of electrical appliances on radio reception so that different devices can function as expected in the same electromagnetic environment. 

Electrosmog, as it's sometimes called, can be transmitted through the air on any radio-controlled device such as a phone, or it can be fed back into the power grid in the form of electronic noise that interferes with the useful sinusoidal waves being transmitted.

New challenges include the Smart Grid and renewable energy

CISPR also deals with the instrumentation and the various methods used for measuring the relevant emission levels. With the advent of the Smart Grid and new methods for generating energy from renewable sources, CISPR is faced with the challenges of ensuring that minimal limits are adapted and integrated in line with the new technologies being developed.

Differentiating noise from the data in Smart Grid transmission

Sources of interference include ignition and electricity supply systems, electric transport systems and industrial, scientific and electromedical radio frequencies, sound and television broadcast receivers, IT (Information Technology) equipment and so on.

Inherently, all electronic equipment – because of the electricity it uses – generates unwanted radio emissions. Any radio receiver such as a television, for example, needs to have its emissions defined by relevant limits that will enable it to receive the air-transmitted signals from all the radio and TV stations to which it is tuned.

When it comes to dealing with the needs of the Smart Grid, CISPR's work involves not only radiated emissions, but also those that are conducted. In order to provide the Smart Grid with the necessary intelligence about when and where power is needed, what is available and so on, it is necessary to be able to exchange and communicate the relevant data along the power lines.

Using the sun's energy brilliantly

The current generated by a PV (photovoltaic) module, for example, is DC (direct current) and has to be converted to AC (alternating current) by inverters in order to be useful for running electrical equipment. The solar inverters are often the most expensive component of a solar energy system.

PV energy can originate from a few simple modules mounted on the roof panels of an isolated house. Alternatively, it may come from a solar farm where there is an entire field of modules converting the energy gathered from the sun. PV power is thus inherently variable in quality due to the wide variety of the installations at which it is generated.

Because the inverters used for the DC to AC conversion for PV energy vary tremendously in wattage and electronic quality, the quality of the AC electricity produced for integration into the Smart Grid also fluctuates. In comparison, power generated from another renewable energy source, hydroelectricity, is purer and more consistent since the sinusoidal waves are produced electronically.

Sensors in meters transmit data for intelligent use

Using PV modules is not just about generating renewable energy, however, it's also about being able to re-inject the power into the Smart Grid. Thus, when there is a surplus of supply it's possible to recuperate some of the costs of the installation by selling it to the utility.

To do so, it's necessary to be able to measure what has been produced and how much of the electricity has been consumed. This type of system relies on sensors mounted in a meter. The meter is connected to the Smart Grid and the information sent through broadband communication to a centre where it can be processed. The intelligence of the system relies heavily on being able to differentiate the frequency and the voltage of the data signal that is sent along the broadband power line from any extraneous electronic noise that happens to be there.

CISPR is working on ensuring that common household appliances and lighting equipment, for example, are designed so that when they are switched from stand-by mode to active mode they do not create any disturbance or trigger unwanted events in the meters that might then be communicated falsely over the Smart Grid.

Setting immunity levels that allow data to be transmitted without interference

The role of CISPR in this respect is to set the immunity levels, and to define and allocate the various acceptable frequency ranges for transmitting the data. In turn, IEC TC 77, is working on defining the International Standards that will allow the electronic noise to be filtered properly so that the data that travels along the line can be recognized and not confused with the noise.

CISPR has set up a Steering Committee Working Group to coordinate future Smart Grid work and ensure that it takes an international uniform approach in protecting the entire spectrum of radio frequencies. The committee is presently drawing up a list of all International Standards it has produced to date that are relevant to the Smart Grid which it will submit to SMB (Standardization Management Board) ACEC (Advisory Committee on EMC).

Annual meeting highlights new challenges

CISPR's annual meetings of subcommittees and working groups and its main plenary held in Seoul, Republic of Korea, in October 2011, presented an opportunity for CISPR to look again at its policy and the driving forces behind its work.

It was also an occasion to present two of its TC experts, Philippe Lancelin and Heesung Ahn, with the IEC 1906 award in recognition of the work they have carried out respectively in SCs (subcommittees) I and B.

Over the two weeks in Korea, 76 experts from 22 countries, together with the CISPR Chairman, Don Heirman of the US (United States), Secretary Stephen Colclough of the UK (United Kingdom) and Technical Officer Pierre Sebellin from IEC Central Office in Switzerland, discussed a variety of new strategies for taking into account the new challenges of connecting devices to the Smart Grid on a global level and transporting the relevant data about the generation and use of energy without interference.

The waveform of an AC power circuit is a sine wave. The waveform of an AC power circuit is a sine wave.
Reading the meters. Reading the meters.
Recipients of 1906 award: Phillipe Lancelin (left) with Heesung Ahn (right) and Don Heirman (centre). Click for larger version. Recipients of 1906 award: Phillipe Lancelin (left) with Heesung Ahn (right) and Don Heirman (centre). Click for larger version.