Hazards presented by fault arcs

Since June 2009 (see  KANBrief 3/09), a KAN working group comprising representatives of the German accident insurance institutions, regional authorities, test bodies, the research community and industry has been intensively addressing the issue of protection against the effects of fault arcs. The group's original aim was to discuss the parameters for the type-testing of clothing for protection against thermal hazards presented by fault arcs. Ultimately, however, the discussions extended beyond this original task.

Fault arcs may arise during work on or near live parts, or may be caused by lightning strikes or foreign objects in electrical installations. They result in the release of huge amounts of energy which can destroy the installation and seriously injure or even kill people in the vicinity.

Protective measures on different levels

Fault arcs are frequently caused by a failure to perform maintenance properly, and occasionally also by the unrestricted addition of further equipment to installations. For this reason, organizational measures taken among users are a very effective way of improving the situation.

However, the hazards should not be reduced by organizational and personal measures alone, but also at the source, primarily by engineered measures such as compartmentalization, insulation or systems for protection against fault arcs. The progressive trend towards reducing the dimensions of installations, particularly in the low-voltage area, may even have increased the overall risk of fault arcs. It would therefore be advantageous for companies to make even greater use of risk assessment in order to identify these causes and effects and to motivate their purchasers to procure fault-arcproof installations.

The accident insurance institutions will issue an information brochure (BGI/GUV-I 5188, "Unterstützung bei der Auswahl der Persönlichen Schutzausrüstung bei Arbeiten in elektrischen Anlagen", publication planned for mid-2012) shortly based upon the latest findings and containing recommendations for the selection of PPE against thermal hazards associated with fault arcs. The brochure is intended to facilitate risk assessment, and also to enable the impact upon human beings to be determined from the characteristics of the installation and the potential emissions.

Further findings of the KAN working group

• Fault arcs give rise to ultraviolet, infrared and visible radiation at high intensities, which may lead to irreversible injury to the skin and eyes. However, visors in accordance with EN 166 (EN 166:2001, "Personal eyeprotection – Specifications") for protection against fault arcs do not provide adequate protection against visible and infrared light. The addition of corresponding provisions to this standard constitutes a major challenge.
• A fault-arc incident may give rise to peak sound-pressure levels of up to 150 dB(C). Only highly effective ear muffs are able to provide any degree of protection against such exposure levels. This situation presents employers with problems. Firstly, acceptance among employees of highly effective hearing protection merely for the very occasional event of a fault arc is likely to be low. Secondly, consideration should be given to the impairment by hearing protection of communication, and the resulting increase in other hazards.
• The fusion and vaporization of materials in the vicinity of a fault arc gives rise to toxic gases and particles. The KAN working group has however chosen not to give priority to these hazards, since current knowledge suggests that other hazards, such as those presented by heat, pressure, noise or radiation, have a much greater impact.

The findings of the KAN working group confirm that even better protection needs to be provided against hazards associated with fault arcs.

No progress at CENELEC

To date, the standardized procedures available at European level have been limited to those for testing of the materials used for protection against thermal hazards. From the perspective of prevention, it is crucial that a harmonized standard also be published to serve as a test specification for the protective clothing. Unfortunately, the required work on prEN 61482- 2 (prEN 61482-2:2007, "Live working – Protective clothing against the thermal hazards of an electric arc – Part 2: Requirements") ground to a halt over two years ago. KAN urgently calls upon the secretariat and chair of CLC/TC 78 to revise and adopt this document. Success may be expected however only if the OSH stakeholders of other European countries also motivate their national delegations to adopt the same approach.

Corado Mattiuzzo
mattiuzzo@kan.de