May 10, 2018
By: Jeson Pitt
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Employee safety is of paramount importance to any industry. One way to ensure this is by conducting arc flash risk assessment. Referring to Arc Flash Hazard Study and Analysis will be helpful as this document defines equations and methods that have become key components of the arc flash study.
Let’s look at the processes involved in Arc Flash Hazard Study and Analysis.
1. Short Circuit Calculations: Data is gathered to make calculations to identify the bolted and arching fall levels at key points in a power distribution system.
2. Protective Device Coordination: An electrical systems coordination study is performed to determine the duration of the arching faults.
3.Arc Flash Hazard Calculations: The incident energy level, the flash hazard boundary, and the PPE required is calculated for each location.
4. Documentation: All the information gained from the studies are turned into a comprehensive report that contains all the necessary information required to comply with regulatory requirements.
5. Unsafe Work Locations: This report will identify all the work locations that have the incident energy level in excess of available PPE ratings.
6. Arc Flash Hazard Mitigation: In this step, recommendations are made for minimizing the arc flash hazards caused by changes in system protection or operational procedures.
7. Arc Flash Hazard Labels: Field labels will be given to the customers. These labels contain the flash hazard boundary distance, PEE category, incident energy level, shock category and shock hazard for each location.
Steps to Complete an Arc Flash Analysis
In order to perform an arc flash hazard analysis, you must collect necessary data about the facility’s power distribution system. This data includes the details of the arrangement of components on a one-line drawing and nameplate specifications of every device. The lengths and cross-section of all cables are also included.
You can contact the utility team for details about the minimum and maximum fault currents that can be expected at the entrance. Further, you must study the modes of operation to study the worst case scenarios which may cause arc flash.
Engineering Analysis of the Data
After you collect the data, perform a short circuit analysis that is followed by a coordination study. Feed the resultant data into the equations described by NFPA 70E-2000 or IEEE Standard 1584-2002. These equations produce the necessary flash protection boundary distances and incident energy to determine the minimum PPE requirement.
Conduct a short circuit study to determine the magnitude of current flowing throughout the power system at all the critical points at different time intervals after a ‘fault’ occurs. Use these calculations to determine the bolted fault current as it is important to calculate the incident energy and interrupting ratings of the equipment. Comparing equipment ratings with calculated short circuit and operating conditions will identify underrated equipment.
Protective Device Coordination
Perform protective device coordination to ensure selection and arrangement of protective devices to limit the effects of an overcurrent situation to the smallest area. Use the results to make recommendations for mitigating arc flash hazards.
Arc Flash Calculations
Determine the incident energies and flash protection boundaries for all your equipment. The incident energy is the energy needed for an arc flash to cause second-degree burns and flash protection boundary is the distance where the incident energy or second-degree burns are caused. Complete the calculations of incident energy levels and flash protection boundaries for all relevant equipment busses.
Arc Flash Study and Analysis Report
Once the calculations are done, prepare the Arc Flash Report, which provides a short review period during which your team can evaluate modifications. Deduce the reports results carefully.
Lastly, create and install arc flash warning labels which pinpoint incident energy and working distance, arc flash boundary, and nominal system voltage. Include Limited, Restricted and Prohibited approach boundaries, date, upstream protective device and recommended personal protection equipment (PPE) as well.
Numerous industrial, institutional and commercial electrical systems and construction electrical products are prone to arc flash hazards. By individually analyzing these systems and labelling the arc flash boundary, you can increase personnel and workplace safety tremendously along with reducing shock hazards and arc flash injuries.