Electrical Apparatus magazine, November 2004 Dealing With Workplace Arc Hazards

We usually think of "electrical safety" as avoidance of shock. However, in the industrial workplace, many persons are injured or killed each year without ever contacting energized conductors. Instead, they are victims of the explosive effects of electrical arcs.

Flash burns can be serious at distances of several meters from an arc, the current in which may be 50,000 to 100,000 amperes. Arcing faults are a growing concern because:

1. Economic pressure has reduced the frequency of electrical maintenance and the time allotted to its performance.

2. Personnel cutbacks have reduced the number of experienced technicians

3. Electrical systems are capable of producing higher fault currents.

4. Electrical equipment is aging.

5. Workplace safety standards in general have assumed growing importance in U. S. industry.

New standards deal with arc hazards in several ways. The 2004 edition of Standard 70E (National Fire Protection Association) specifies workspace boundaries defining several degrees of risk and the required distances between workers and energized conductors. An important one is the flash protection boundary at which maximum radiant energy from an arc will cause only curable (second degree) burns. Working within such a boundary requires protective equipment such as face shields or hoods and melt-resistant clothing.

To determine the safe distance, complex calculations in IEEE Standard 1584 (based on extensive laboratory tests) involve electrical system characteristics such as available fault current and protective device clearing time.

A second important consequence of high-power arcing is the blast pressure wave. Explosive pressure on an exposed person can collapse lungs and rupture eardrums, even though the victim may not be burned. That impact can also throw a worker off balance or against a wall to suffer serious injury. As with any explosion, flying fragments of metal can be damaging at even greater distances. A new Fire Protection Research Foundation project has been undertaken to more thoroughly investigate the blast effect.

These standards, applied with caution in conjunction with strong safety training, should reduce the electrical accident rate, But sound system design and maintenance practices remain essential to this effort.

Industry news...

Featured Technical Article
November 2004

On this page is a summary of the Electrical Apparatus November 2004 featured technical article, by Richard L. Nailen, P.E. , "Dealing With Workplace Arc Hazards" Der Umgang mit den Gefahren der Bogenentladung am Arbeitsplatz ... Comment adresser les risques d'arc électrique au lieu de travail ... Cómo enfrentar los riesgos de arco eléctrico en el lugar del trabajo...

To order backissues which contain the foreign language summaries and the full article, call 312-321-9440 or visit our online webstore. See also links to additional technical summaries, below.

For our international readers, summaries of the technical articles are provided in German, French and Spanish. (Summaries do not appear when the article is U.S.-specific.)

 

Advertising for the March Electrical Apparatus closes February 15. Classified ads close February 20. (Space is sometimes available after the closing date - call 312-321-9440.)