Arc flash hazard analysis

01/01/2008 - Volume IV - Issue I

NFPA 70E Article 130.3 requires that an electrical flash hazard analysis be performed to assure that workers are properly protected whenever they work on or near equipment that is not in an "electrically safe condition." A flash hazard analysis helps provide employee safety against dangers associated with the release of energy caused by an electrical arc.

 

What is an arc flash event?

 

An arc flash event, or an arcing fault, is the movement of electricity through air between two conductors.

 

What are the dangers of an arc flash event?

 

An arc flash event is caused by a breakdown or loss of insulation integrity between two energized sources or an energized source and ground that will allow current to flow through air between the two. Some arc faults are due to human error, such as accidental contact with energized parts and dropped tools. Arcing faults can also be caused by a buildup of impurities on insulating surfaces that allow for a current path. Wildlife can also cause arcing faults by damaging insulation or by crossing between phases.

 

What is an arc flash hazard analysis?

 

Arc flash hazard analysis is a study to determine potential energy that personnel could be exposed to at specific points in an electrical system.

Key elements of arc flash hazard analysis are:

  • Calculating arc energy levels, flash hazard boundaries, and NFPA based level of personal protective equipment (PPE) at each evaluation point.

  • Communicating PPE and approach distance to exposed energized equipment through a warning label system.

  • Identifying analysis points where arc flash energy levels may be reduced by improvements to system protection.

Is there anything I can do to reduce the arc flash hazard?

 

In many cases, a settings adjustment on a circuit breaker, a relay, or switching to a current limiting fuse can reduce the arc flash energy. Setting circuit breakers and relays can be changed manually, but some protective devices also feature multiple set-points that can be changed with a switch.

 

What information do I need to have an arc flash hazard analysis done for my facility?

 

In order to perform an arc flash hazard analysis, the following information is required:

  • One line diagram of the power distribution system

  • Setting of existing devices

  • Current copy of power system short circuit and coordination study

  • Preliminary close estimate desired at each location

  • Upstream protective device type, size, and settings (if any).

What can I do if I do not have this information?

 

If you do not have the available short circuit currents or the protective device information, you will need to contact a trusted industry partner such as Siemens that performs short circuit studies as well as arc-flash studies. You can help mitigate risks with a comprehensive arc flash hazard study by Siemens. With over 100 years of experience in analyzing power systems, Siemens employs only proven data collection methods, detailed calculations, and thorough software-based analysis to identify the calculated incident and NFPA based PPE for each potential hazard.

 

Sample of customer deliverables:

  1. Calculating arc energy levels, flash hazard boundaries, NFPA based level of personal protective equipment (PPE) at each evaluating point.
  2. Communicating PPE and approach distance to exposed energized equipment through a warning label system.
  3. Identifying analysis points where arc flash levels may be reduced by improvements to system protection.