How Often Do I Need to Conduct an Arc Flash Hazard Analysis?

This month’s blog is going to focus on performing and arc flash hazard analysis.  In order for employees to work on exposed live (energized) circuits, an arc flash hazard analysis is needed to determine the incident energy available at the equipment and what personal protective equipment (PPE) is needed to work safely.

To perform an arc flash study of the electrical system, there are some background items that are required.  The first and foremost is an updated single-line drawing (SLD) or one-line drawing.  A single-line drawing is an electrical schematic of the electrical system of the facility.  This should include all switchgear, switchboards, panelboards, transfer switch equipment (automatic or manual), uninterruptible power systems (UPS), transformers, motors, variable speed drives (VFDs) or adjustable speed drives (ASDs), disconnecting devices.  In addition, information on conductors, e.g. size, number, lengths, supporting mechanisms (tray, conduit, air) are also required.  Information is also required on the service transformers and protective devices used by the electrical utility that feeds your facility.

Overcurrent protective devices, e.g. circuit breakers and fuses, are also required.  For information required for fuses include Class, Ampere Rating, Manufacturer and Type.  For circuit breakers, the information required includes Manufacturer, Type of breaker (LVPB, ICCB, MCCB), trip type (thermal-magnetic, electronic), and all associated settings.

Once the single-line drawing is complete, an electrical model can be constructed – while standards allow for the use of hand calculations or simulations, hand calculations can be become cumbersome.  Once the model is constructed, and arc flash hazard analysis can be conducted.  Standard simulation tools are available from SKM, ETAP, and EasyPower.  The analytical techniques that can be utilized to conduct an arc flash hazard analysis are described in IEEE Guide for Performing Arc-Flash Hazard Calculations, IEEE 1584 and the Standard for Electrical Safety in the Workplace, NFPA 70E.  There are minimal differences between the model calculations.

 

Single-Line Diagram (SLD)

The arc flash analysis of the electrical system in the facility will provide the following outputs:

• Arc flash boundary
• Incident energy
• Shock hazard voltage
• Shock hazard boundaries
• Limited approach boundary
• Restricted approach boundary
• Prohibited approach boundary

Once the arc flash hazard analysis has been conducted, all equipment is labeled, and personnel are trained to work safely around exposed live (energized) circuits, is there more work to be done?

YES, there is more work that needs to be done.  The Standard for Electrical Safety in the Workplace, NFPA 70E states in Article 130.5 that an arc flash study needs to be reviewed every five years or whenever there is a significant change in the electrical system.  The five year interval is straight-forward requirement.  Determining a significant change can be left up to interpolation.

Whenever there are changes to the electrical system, the single-line diagram must be updated and the arc flash hazard analysis needs to be reviewed.  While the addition of small motors or new equipment may not affect the arc flash boundaries or incident energy of existing equipment, you will need this information to label the new equipment.  Major changes to the electrical system, e.g. new electrical service, the addition of large motors, facility expansions, etc. can result in the amount of incident energy at existing equipment.  This can require an update to all equipment labeling, and re-training of employees who work on exposed live (energized) circuits.  Even if there are no changes in the electrical system, a review of the arc flash hazard analysis is required at least every five years [1]. 

The review of the arc flash hazard analysis should be conducted in a formal manner.  This requires documentation.  Documentation can include reports of the analysis, meeting notes, and process reviews associated with any change management system used by your organization.  I recommend that all quality documentation related to the arc flash hazard review be keep on file for at least three cycles – the current arc flash hazard analysis plus to the past two arc flash hazard analyses.

On another note, the numbers of user of the Day-One-Safety checklist continues to grow.  I appreciate everyone who is using this tool.  This is another item in your toolbox to help keep your employees safe when working at various facilities.

If you are unfamiliar with the Day-One-Safety checklist, this software application is intended to assist people with working in new or unfamiliar facilities or locations.  This is a free on-line checklist available to anyone who wants would like to use it – and I will not hassle you to buy something in return.  To request a password send me an email at cole3250@gmail.com or to Login, click here.

References:

1. National Fire Protection Association (NFPA). Standard for Electrical Safety in the Workplace, NFPA 70E-2012.  Quincy, MA USA.