Arc flash analysis is conducted by first collecting data about the components of a power distribution system. This data involves the arrangement of electrical equipment found in a single-line drawing with nameplate specifications of every piece of equipment. The details of the lengths and cross section area of all cables are also required. The electric utility should be contacted for information including the minimum and maximum fault currents that can be expected at the entrance to the plant. Once all of this data has been collected, at that time, a short circuit study followed by a coordination study should be conducted. The resulting data can then be fed into the equations described by either NFPA 70e-2004 or IEEE Standard 1584-2002. 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.
Arc flash analysis includes:
- Potential arc flash incident energy levels
- Flash protection boundary distances
- Safety training
- Selecting personal protection equipment
- Electrical equipment labeling recommendations
There is arc flash analysis software available that automatically estimates the Incident Energy released in the event of an arc fault and determines the required Flash Protection Boundary.
Such arc flash analysis 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.
Arc flash analysis software also helps to design safer power systems and to comply with OSHA regulations by using the NFPA 70E-2004 or IEEE Std. 1584-2002 and 1584a-2004 calculations.
It 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. 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 arc flash analysis 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 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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