FREQUENTLY ASKED QUESTIONS

What is arc flash?

• NFPA 70E: “A dangerous condition associated with the release of energy caused by an electric arc”
• Blinding flash of light followed by a deafening explosion
• Large amount of energy discharged from electrical equipment with hot gases and molten metal
• It will leave an indelible impression on you for the rest of your life

How is arc flash caused?

• Electrical insulation failure or insulation system can no longer withstand the applied voltage
• Inserting tool in wrong place or dropping into an energized area
• “Accidental” contact with energized electrical parts

What type of damage does it cause?

• Serious bodily injury or death
• Permanent irreparable equipment damage
• Loss of plant production
• Plant wide outages

What are the latest arc flash injury statistics?

• Capelli-Schellpfeffer: 10 to 15 workers in U.S. injured daily
• 1 to 2 deaths every day

What can you do to protect yourself against arc flash?

• Avoid energized electrical work if possible
• Use properly rated PPE for given task
• Know hazard risk involved before working

Can the energy from an arc flash be predicted before it occurs?

• Yes, can be computed using power system analysis
• Dependent on OCPD tripping time and available fault current
• Routine PM of electrical equipment is key

Can arc flash energy be mitigated?

• Yes, by adjusting OCPD settings or using device with more “flexibility”
• Must keep equipment protective boundaries and load inrush requirements intact

Is an arc flash study expensive? How much does it cost?

• Study cost is dependent upon size, configuration, and sophistication of electrical power system under study
• Determine total number of electrical components installed by examining existing single line electrical drawings (SLD’s)
• Study completion time is proportional to total number of electrical components installed

What if we do not have any drawings of our plant’s electrical system?

• Developed a MS Excel spreadsheet for “document challenged” clients to help us prepare a cost proposal
• Allows clients to enter quantities for each specific type of electrical component installed

What if the drawings provided for the proposal are inaccurate?

• IEEE-1584 requires that power system SLD’s are field verified prior to performing AFHA
• If SLD’s provided by client are inaccurate, we cover ourselves by providing a disclaimer that states our proposal is based upon a specific component quantity
• Change order will be requested if this number is exceeded

After the AFHA is done, what type of information will be provided?

• Warning labels for all applicable equipment where energized work may be performed (NEC-2008 Art. 110-16 )
• Comprehensive written report of the arc flash and short circuit study results
• AFHA mitigation study to reduce the IE levels of the hazard and an overcurrent protective device coordination study to insure that devices trip in the correct sequence

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