Arc Flash Analysis

By R.W. Hurst, The Electricity Forum

Arc Flash Analysis
Arc Flash Analysis

An arc flash analysis is an engineered incident energy study which is conducted to establish safety protocol for qualified electrical personnel required to work on electrical equipment and circuit parts that cannot be placed in an electrically safe work condition. 

Protocol such as proper levels of PPE based on both the shock and arc flash boundaries are defined by the calculated incident energy. Other benefits of an engineered arc flash analysis include a short circuit & coordination study and updated facility electrical documentation including one-line diagrams and electrical equipment locations.

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It is important to understand the process and the “behind the scenes” details of an arc flash study. In general, the following seven steps are required for the completion of a thorough arc flash study:


  • STEP 1: Acquire existing as-built documentation
  • STEP 2: Field verification
  • STEP 3: Loading Information
  • STEP 4: Run a Short Circuit Study
  • STEP 5: Selective coordination
  • STEP 6: Arc Flash Evaluation
  • STEP 7: System Evaluation


A study is best conducted by first collecting data about the components of an electrical power distribution system. This involves the collection of data about electrical equipment which should be found in single line diagrams with nameplate specifications of every piece of equipment.

Other details that are required involves the lengths and cross section area of all cables are also required. Remember, you should contact your electric utility for information including the minimum and maximum fault currents that can be expected at the service entrance. Once all of this data has been collected, a typical short circuit study followed by a coordination study can be conducted. The resulting data can then be fed into the arc flash study equations described by either NFPA 70e or IEEE Standard 1584. These equations will produce the necessary arc flash protection boundary distances and incident energy to determine the minimum personal protective equipment (ppe) that is required.



  • Collect system and installation data
  • Determine system modes of operation
  • Determine bolted fault current
  • Calculate arc fault current
  • Find protective device characteristic and arc duration
  • Select working distances
  • Calculate incident energy
  • Calculate flash protection boundary
  • Determine PPE (risk hazard) category

There is software available on the market that automatically estimates the Incident Energy released in the event of an arc fault and determines the required Flash Protection Boundary.

Such studies are performed in conjunction with either ANSI/IEEE or IEC 3-phase bolted short circuit calculations. It determines the required Personal Protective Equipment (PPE) Arc Rating (ATPV) along with the suitable NFPA 70E Approach Boundaries to live parts for shock protection.

Analysis software also helps to design safer power systems and to comply with OSHA regulations by using the NFPA 70E-2004 or IEEE Std. 1584 and 1584a calculations.

An analysis is performed in conjunction with either ANSI/IEEE or IEC 3-phase bolted short circuit calculations. It determines the required Personal Protective Equipment (PPE) Arc Rating (ATPV) along with the suitable NFPA 70E Approach Boundaries to live parts for shock protection.

Electrical hazards and worker safety continue to be a highly discussed topic. Recent changes to recognized industry codes and standards along with an increased interest by the Occupational Safety and Health Administration (OSHA) have highlighted the concern and need to reduce potential hazards with circuit parts and circuit breakers. Visual presentations, an explanation of how to reduce hazards by utilizing the proper overcurrent protective device and a review of Personal Protective Equipment (PPE) and safe work practices, can all be used to reduce hazards.

The calculations and data in calculators and procedures used for determining incident energy exposure, level of PPE, protection boundary are based upon IEEE Standard 1584, Guide for Performing Hazard Calculations. The methods for determining incident energy exposure from this IEEE 1584 standard were created so that the level of PPE selected from the calculated arc flash incident energy would be adequate to protect the torso against incurable burns for 98 per cent of incidents. In up to 2 per cent of incidents, serious injury, incurable burns to the torso, and death could result. (Equations are also provided in IEEE 1584 to cover 95 per cent of incidents, but this calculator utilizes the more conservative equations related to 98 per cent of incidents.) Calculations are based upon PPE with standard ATPVs of 1.2, 8, 25, 40 and 100 cal/cm2. PPE with intermediate ATPV values can be utilized, but at the next lower standard ATPV rating.

PPE must be utilized any time that work is to be performed on or near energized electrical equipment or equipment that could become energized. Voltage testing while completing the lockout/tagout procedure (putting the equipment into an electrically safe work condition) is considered as working on energized parts per OSHA 1910.333(b). As a general work practice, it is suggested that, at the very minimum, the worker utilize voltage rated gloves with leathers, long sleeve cotton shirt, heavy-duty cotton pants, a face shield, safety glasses and hard hat, in addition to the recommendations from NFPA 70E (even though NFPA 70E requirements do not require all these items for the lower Hazard/Risk Categories).

Note: Employees must wear and be trained in the use of appropriate protective equipment for the possible electrical hazards with which they may face. Examples of equipment could include a hard hat, face shield, flame resistant neck protection, ear protectors, Nomex™ suit, insulated rubber gloves with leather protectors, and insulated leather footwear. All protective equipment must meet the requirements as shown in the latest edition of NFPA 70E. Protective equipment, sufficient for protection against the potential electrical fault, is required for every part of the body. The selection of the required thermal rated PPE depends on the incident energy level at the point of work.

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