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
- 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
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
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-2014 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 ensure that devices trip in the correct sequence