Arc Flash Studies / NFPA 70E...

What is an Arc Flash?

An Arc Flash is an electrical explosion due to a fault condition or short circuit when either a phase to ground or phase to phase conductor is connected. Arc flashes cause electrical equipment to explode, resulting in an arc-plasma fireball. Temperatures may exceed 35,000° F (the surface of the sun is 9000° F). These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc blast will likely vaporize all solid copper conductors which will expand up to 67,000 times its original volume when it is vaporized. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people.

Why are Arc Flash Studies Required?

  1. 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. OSHA 29CFR 1910.335 (a) (1)(i) requires the use of protective equipment when working where a potential electrical hazard exists and 29CFR 1910.132(d)(1) which requires the employer assess the workplace for hazards and the need for personal protective equipment. OSHA compliance is required by any plant building or facility.
  2. The National Fire Protection Association (NFPA) Standard 70 - 2002 "The National Electrical Code" (NEC) contains requirements for warning labels.
  3. NFPA 70E 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. Part II 2-1.3.3 regarding Arc Flash Analysis states that a "Flash Hazard Analysis shall be done before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrical safe work condition". This Arc Flash Hazard Analysis must be done to determine the level of Personal Protection Equipment PPE that a worker must use, and the Arc Flash Boundary in inches along with the incident energy found at each location. Each panel must be marked with an ANSI z535 approved Arc Flash Warning Label.
  4. The Institute of Electronics and Electrical Engineers (IEEE) 1584 - 2002 Guide to Performing Arc-Flash Hazard Calculations

What steps are required for an Arc Flash Report/Analysis?

Electrical documentation of all systems data and node information. (Following NEC110.22)

  • Conductor sizes, lengths, and quantities
  • Transformer nameplate data
  • Circuit breaker part numbers and trip settings
  • Fuse ratings and other electrical data

What steps are required to complete a Coordination Study?

  1. Development of a Single Line Power Riser
  2. Development of the ARC Flash Report
  3. Documentation of all Electrical Arc Flash Categories
  4. Development of all breaker trip curves
  5. Development of Arc Flash Labels and Reports
  6. Installation of all Arc Flash Labels on all power panels, disconnects, switchgear, and transformers
  7. Delivery of all Arc Flash Reports and Single Line Risers