This paper is prepared to give a nonengineering description of Electrical Arc Flash. The hazards associated with an Electrical Arc Flash can be significant resulting in equipment damage, loss of production, bodily harm or even death. This paper is arranged as a series of typical questions and their associated answers.

What is an Electrical Arc Flash?
An Electrical Arc Flash is defined as a condition when electric current passes through ionized gases in the air. Everybody is familiar with naturally occurring Electrical Arc Flashes —lightning; our discussion shall be confined to the unnaturally occurring variety of Arc Flashes—electrical faults. The essential need to first reconcile utility bills and then calculate charges for each tenant is often stymied by an avalanche of confusing rules, rates, and end user surcharges. To make matters worse, many buildings have obsolete or unreliable metering systems to track data.

What causes Electrical Arc Flashes?
An Electrical Arc Flash occurs when current flows through ionized gases in the air between conductors. These may be opposing phase conductors and/or ground. This condition is normally referred to as an electrical fault or 'short circuit.'

Does every 'short circuit' produce an Arc Flash?
No, electrical faults come in two varieties. The first type of electrical fault is known as a ‘bolted fault’. A bolted fault occurs between solidly connected conductors and simply results in excessive current flowing beyond the design limits of those conductors. This type of fault can be as simple as an overload or the result of an installation error.

The second type of fault is an 'arcing fault.' An arcing fault occurs when the distance between conductors is reduced to the point where the voltage present causes the air to ionize and establish a path for the current to flow. This type of fault normally results from accidental contact between conductors.

How long do Arcing Faults last?
Typically arcing faults have a duration of 0.2 seconds or less, however, based upon the available energy and the condition and reliability of the overcurrent protective device the arc may be sustained until the distance through the air the arc must travel exceeds the ability of the ionized gases to provide a current path.

Can the use of Personal Protective Equipment (PPE) prevent injuries?
The use of proper personal protective equipment will mitigate the effects of an arc flash, however, their use may not eliminate the risks involved. Serious injury or death may still occur even when proper PPE is utilized.

Are there rules governing Electrical Arc Flash protection?
YES! The federal government has established rules for safe work practices, they are listed as part of the Occupational Safety and Health Act (OSHA) 29 CFR 1910, it’s the law. A voluntary standard also exists prepared by the National Fire Protection Association (NFPA). The standard for Electrical Safety in the Workplace is NFPA 70E.

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Who is responsible for Electrical Arc Flash protection?
Everyone is responsible. The standards indicate that responsibility has 'dual' ownership. In simple terms this means that the owner, contractor and employee may all share responsibility equally.

How can the risk of Electrical Arc Flash be reduced?
Shutdown and lockout all sources of energy prior to proceeding with the work. The standards allow for work on energized conductors under very specific situations only and economic hardship is not a valid reason.

How can I comply with the standards?
To comply with the standard you must first know what you have. An Electrical Hazard Survey of your facility will include an inventory of electrical equipment, a short circuit & coordination study, labeling of equipment and its location for degree of risk and identification of the proper PPE required to perform work on energized conductors.

Can the effects of Electrical Arc Flash be reduced?
Yes, several methodologies exist to reduce the amount of energy available or the time that energy is available. These may include changing fuses, modifying equipment to separate conductors, increasing ground impedance or increasing circuit resistance.

Is this going to be expensive?
Costs associated with complying with the standards are going to be relative to the size of the facility and the type, condition and operating voltage of the equipment involved. The costs associated with a single Arc Flash incident (no matter whose fault) can easily reach the $1.5 million mark in direct and indirect expenses. No matter how large or complicated the facility it will not approach that order of magnitude, and besides compliance with OSHA regulations is not voluntary – IT’S THE LAW!