Things you need to know...

Q. What is an arcing fault?

A. An arcing fault is the flow of current through the air between phase conductors or phase conductors and neutral or ground. An arcing fault can release tremendous amounts of concentrated radiant energy at the point of the arcing in a small fraction of a second resulting in extremely high temperatures, a tremendous pressure blast, and shrapnel hurling at high velocity (in excess of 700 miles per hour).

Q. What causes an Electrical Arc?

A. An arc occurs when electric current flows between two or more separated energized conducting surfaces. Some arcs are caused by human error including dropped tools, accidental contact with electrical systems, and improper work procedures. Another common cause of an arc is insulation failure. The fault current's magnetic effect causes conductors to separate producing an arc. Build-up of dust, impurities, and corrosion on insulating surfaces can provide a path for current. Sparks produced during racking of breakers, replacement of fuses, and closing into faulted lines can also produce an arc. Birds, bees, and rodents can also cause the snapping of leads at connections. Back to top.

Q. What can happen if I am exposed to arc flash?

A. Exposure to an arc flash frequently results in a variety of serious injuries and in some cases death. Workers have been injured even though they were ten feet or more away from the arc center. Worker injuries can include damaged hearing, eyesight, and severe burns requiring years of skin grafting and rehabilitation. Equipment can be destroyed causing extensive downtime and requiring expensive replacement and repair. The cost of treatment for the injured worker can exceed $1,000,000/case. This does not include very significant litigation fees, insurance increases, fines, accident investigation, etc. This also does not include process loss to the employer.

Q. What can I do to reduce my risk to arc flash exposure?

A. Worker training, preventive maintenance and an effective safety program can significantly reduce arc flash exposure. Preventive maintenance should be conducted on a routine basis to ensure safe operation.

Q. How do you determine what PPE is required?

A. In order to select the proper PPE, incident energy must be known at every point where workers may be required to perform work on energized equipment. These calculations need to be performed by a qualified person such as an electrical engineer. All parts of the body that may be exposed to the arc flash need to be covered by the appropriate type and quality of PPE. Proper PPE can include Flame Resistant clothing, helmet or headgear, face shield, safety glasses, gloves, shoes, etc. depending upon the magnitude of the arc energy.

Q. What standards regulate arc flash hazards?

A. There are four main regulations governing arc flash.
They include:

• OSHA Standards 29-CFR, Part 1910. Occupational Safety and Health Standards. 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices and references NFPA 70E.
• The National Fire Protection Association (NFPA) Standard 70 - 2002 "The National Electrical Code" (NEC) contains requirements for warning labels.
• NFPA 70E 2000 provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized.
• The Institute of Electronics and Electrical Engineers (IEEE) 1584 - 2002 Guide to Performing Arc-Flash Hazard Calculations.

Q. Who enforces these new standards?

A. OSHA is an enforcer of safety practices in the workplace OSHA 1910.132(d), and 1926.28(a) states that the employer is responsible to assess the hazards in the work place, select, have, and use the correct PPE, and document the assessment. Though OSHA does not, per se, enforce the NFPA 70E standard, 2000 Edition, OSHA considers the NFPA standard a recognized industry practice and the administration's field inspectors carry with them a copy of the NFPA 70E and use it to enforce safety procedures related to arc flash. The employer is required to conduct hazard assessment in accordance with 29CFR1910.132(d)(1). Employers who conduct the hazard/risk assessment, and select and require their employees to use PPE, as stated in the NFPA 70E standard, 2004 Edition, are deemed in compliance with the Hazard Assessment and Equipment Selection OSHA Standard. Electrical inspectors across the country are now enforcing the new labeling requirements set forth in the 2002 National Electric Code (NEC).

Q. What data is required to be on the new arc flash warning labels?

A. 110.16 only requires the label state the existence of an arc flash hazard. It is suggested that the party responsible for the label include more information on the specific parameters of the hazard including:

• Available Short-Circuit Current
• Flash Protection Boundary
• Incident energy at 18" expressed in cal/cm2 PPE required
• Voltage shock hazard
• Limited shock approach boundary
• Restricted shock approach boundary
• Prohibited shock approach boundary

Q. What is the difference between NFPA 70E and IEEE 1584 calculations?

A. NFPA 70E method estimates incident energy based on a theoretical maximum value of power dissipated by arcing faults. This is believed to be generally conservative. In contrast, IEEE 1584 estimates incident energy with empirical equations developed from statistical analysis of measurements taken from numerous laboratory tests.

Q. What is a flash hazard?

A. A flash hazard is defined in NFPA 70E as a dangerous condition associated with the release of energy caused by an electric arc.

Q. What is the flash protection boundary?

A. The flash protection boundary is the distance from the arc source at which the potential incident heat energy from an arcing fault falling on the surface of the skin is 1.2 calories/cm2.

Q. What is "Limited Approach Boundary"?

A. The limited approach boundary defines a boundary around exposed live parts that may not be crossed by "unqualified" person unless accompanied by "qualified" persons.

Q. What is "Restricted Approach Boundary"?

A. The restricted approach boundary is the area near the exposed live parts that may be crossed only by "qualified" persons using appropriate shock prevention techniques and equipment.

Q. What is "Prohibited Approach Boundary"?

A. The prohibited approach boundary is the area near exposed live parts that may be crossed only by "qualified" persons using same protection as if direct contact with live parts is planned. This is defined by the nominal voltage.

Q. What is the definition of a "qualified" person?

A. A qualified person is one who has received documented training in the hazards of working on energized equipment in general, and has been trained in the hazards of the particular equipment to be serviced. Training must include the use and proper application of PPE.

Q. What is an Arc Flash Study/Analysis?

A. An Arc Flash Study/Analysis is an engineering study that determines the amount of current that could flow at any point in an electrical system, and the timing required for the nearest circuit protective device to operate to clear a fault.

Q. What is the hazard/risk category?

A. The hazard/risk category is specified as a number representing the level of danger, which depends upon the incident energy. The category ratings range from 0 to 5 where category 0 represents little or no risk, and category 5 is the most dangerous.

Q. What is "incident energy"?

A. Incident energy is defined in NFPA 70E as, "the amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event."