Many users of LV switchgear and controlgear assemblies have underlined the question of safety in electrical assemblies with reference to one of the most severe and destructive electrophysical phenomenon - the electric arc. This very complete ABB technical paper explains the issues and shows how the LV assemblies concerned should be designed, built and tested in compliance with the state-of-the-art:
Many users have underlined the question of safety in electrical assemblies with regard to electric arcs. Unlike tripping devices, for which arc phenomena represents one of the standard operating conditions, in LV switchgear the electrical arc is a rare event. But, if an arc occurs inside LV switchgear, it generates internal overpressures that result in local overheating that may cause high mechanical and thermal stresses in the equipment. Moreover, the involved materials can generate hot decomposition products, gases or fumes, which, because of the overpressure, are almost always ejected to the outside of the enclosure - jeopardising operator safety.
European Directive 2006/95/EC states the fundamental safety requirements for low voltage electric materials (from 50V to 1000V AC, from 75V to 1500V in continuous current) to be put on the market within the EC. Among the essential safety requirements defined by this Directive, particular importance is given to the need of taking technical measures to prevent 'temperature rises, electric arcs or radiations which may result in hazards' from occurring. This aspect has always been highly considered for apparatus, but it has been wrongly neglected for electrical switchgear, and only in the last 10-15 years it has been catching on.
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