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Arc Flash and Arc Blast
10 questions By Tony R. Kuphaldt
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Question 7 of 10
What type of personal protective equipment (“PPE”) is recommended for protection against arc flash and arc blast?
Reveal answerThe PPE recommended for arc flash/blast protection is very similar to the “bunker gear” worn by professional firefighters. Research this and be prepared to discuss the particular details with your classmates.
Notes:The hazards of arc flash and arc blast are quite similar to the hazards faced by professional firefighters in their jobs, hence the similarity in protective equipment.
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Question 8 of 10
Arc flash may occur when using a voltmeter to measure voltage in a 480 volt electrical system, if there happens to be a power line transient (from a lightning strike, perhaps) at that time. Some industrial voltmeters carry a “CAT” rating (CAT I, CAT II, CAT III, CAT IV, etc.) specifying their tolerance for overvoltage transients, and subsequent safety provisions.
Describe in detail the meaning of these “CAT” ratings, and the nature of the hazard posed by a meter that fails under transient conditions.
Reveal answerThere is a substantial amount of information available on this subject on the internet, and through meter manufacturer publications. I will leave the research to you!
Notes:This question makes the point that personal protective equipment (PPE) is not the only line of defense against the hazards of arc flash. Test instruments also play an important role in electrical safety (or may contribute to the danger!). It is very important that electrical workers use quality tools for their work. A CAT-rated multimeter will cost more than one without a similar safety rating, but tell your students that the medical expenses incurred by an arc flash accident are far greater!
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Question 9 of 10
A potential cause of arc flash, and perhaps even arc blast, is improper meter use. Describe how an ammeter could be mis-applied to a live circuit in such a way that it causes an arc flash or arc blast.
Reveal answerNever, never connect an ammeter across two points in a circuit with substantial voltage between them!
Notes:Discuss with your students why an ammeter should never be connected across a voltage source, especially a voltage source in an electrical power system. Relate this to the ideal input resistance of ammeters, and to Ohm’s Law.
