Sign of the times

From symbols to communication in a digital world

The work of IEC Technical Committee 3 has much evolved since the early days of the IEC, partly as a result of the gradual digitalization of our societies.

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Stand-by symbol developed by IEC TC 3

IEC TC 3 is one of the early technical committees of IEC. It was set up in 1911 to produce standards for graphical symbols. The aim was to provide those working in the budding electrical industry with the same graphical representations to be used on electrical devices, systems and parts. Graphical symbols were necessary for technical documentation as well as to help human interaction with equipment.

The power of symbols

One of the most well-known representations developed by IEC TC 3 is the standby symbol, indicating a sleep mode or low power state on electrical devices. This world-famous symbol has become a bit of an icon for techies around the globe. Like all the other symbols used for electrotechnical equipment, it can be found in a database published by both IEC and ISO (IEC 60417 and ISO 7000). The IEC part of the database is maintained by subcommittee (SC) 3C. “We also provide a database of symbols for diagrams, IEC 60617. It includes around 1900 symbols,” explains IEC TC 3 Chair Eirik Selvik from Norway. Both are horizontal documents used across IEC by all the various TCs.

A validation team including representatives from IEC National Committees checks the symbols on an ongoing basis. “Each symbol is standardized separately and we have to make sure that they continue to be used throughout industry,” Selvik adds. The symbols represent conductors and connecting devices, semiconductors and electron tubes, measuring instruments, lamps and signalling devices, etc… Each symbol is shown “as is” in the databases. “Rules for the application of these symbols, especially in documentation, are provided in IEC 61082, a horizontal publication specifying the preparation of documents used in electrotechnology,” Selvik says.

Changing focus

The work of TC 3 does not stop there, however. Its emphasis has shifted towards the management of information and the creation of computer interpretable classification and identification systems used during the whole life cycle of a device, system or plant.

IEC SC 3D works on the Component Data Dictionary (CDD) specified in the IEC 61360 series of standards. It is a technical dictionary for use in the electrical and electrotechnical domain. This work is essential for enabling the exchange of technical data and facilitating interoperability.

“The move from a paper to a digital world started in the 1980s. We gradually changed our focus to finding a way to convey information so that it meets new digital needs,” adds Selvik.

2019 has already been a busy year for the TC, with several new editions of standards. “We issued a new version of IEC 61293 at the end of the summer. The initial standard was published in 1994 by TC 16. The group was disbanded in 2012 and TC 3 took over that part of its work. It is a horizontal publication which establishes minimum requirements and general rules on marking electrical equipment with ratings. We had to include new information concerning AC and DC supply aspects which had changed. The publication is part of the work we do on safety applications for human machine interfaces.”

Another new edition is IEC 81346-2. “Part 2 of the standard deals with classification schemes and their associated letter codes for the defined classes. This second edition states how to define classes and make different classes of objects. We have defined a hierarchy, including entry classes, sub-classes and sub-sub classes,” Selvik describes.

Like IEC 61293, the new edition of IEC 81346-2 is a horizontal publication which can be used by all IEC TCs but, even more, can be applied throughout all technical areas and branches of industry, whether energy, chemical, construction, automotive, shipbuilding and marine, etc. "This standard is widely used throughout different industries. We are very glad to have published this second edition. We share the work with ISO on the overall series. ISO/IEC 81346 part 1 and 2 is managed by IEC, while ISO deals with other parts, such as 10 and 12,” says Selvik.

Cooperation with ISO is a routine occurrence. “It is rare to have documentation which is only relevant to electrotechnical issues. We work a lot with ISO TC 145 on graphical symbols, for instance,” Selvik says. The TC also works with the Institute of Electrical and Electronics Engineers (IEEE). “We developed the IEC/IEEE 82079-1 standard together. We worked on the second edition, which was issued in May, with  ISO TC10/SC 21 and the Institute. We cooperated with its systems and software engineering standards committee. This second edition is much broader than the previous standard.”

General Meeting: we need feedback!

IEC TC 3 will be holding a workshop in Shanghai to present topics the committee is working on. It will take place on October 24 at 9:00 in the Pudong Shangri-la River Wing building. "We really want people from other TCs to attend because they are our customers, to some extent. We would like them to express their specific needs for graphical symbols, documentation and representations. Our ultimate goal is for end users to receive consistent, unambiguous and coherent documentation providing the knowledge they need.”

Feedback is therefore required and there is no better place to start than at the IEC GM.