Recent changes to IEEE 1584-2018 and NFPA-70E 2021 impact how arc flash is handled in industrial facilities. These updates can be complicated, so we’ve laid out three of the most common points of confusion along with recommended actions.
Well Maintained Gear
Gear is required to be “well maintained” for live work, but the term is muddy and can lead to disagreements when setting up safety procedures. One note suggests well maintained means gear that has been maintained in accordance with the manufacturer’s recommendations and applicable industry codes and standards. While this seems straightforward, it really isn’t possible to visually identify if equipment is properly maintained, and maintenance documentation is not generally well tracked.
In practice, well maintained means: breaker testing every three to five years, annual infrared scans, no after-market modifications outside manufacturer specifications, and gear that’s in good condition (i.e., not hit by a skid steer). You should check if gear is well maintained as part of the pre-job hazard assessment (PJHA).
I Create a preventative maintenance (PM) plan for electrical equipment that may need to be opened live.
I Include any critical vendor maintenance recommendations in your plan.
I Review maintenance work to ensure proper hardware is used.
I Label equipment that is not to be opened live due to physical damage or concerns the gear is not well maintained.
PPE Levels vs. Cal/cm2
While there isn’t too much confusion on PPE levels vs. incident energy (Cal/cm2) from a safety-management standpoint, the change to only considering incident energy has led to many inconsistencies in language. To be clear, NFPA 70E only considers the incident energy calculation and states your PPE must be rated higher than the calculated hazard. While most levels match the old level definitions, there are some variations. If the PPE levels match the NFPA 70E PPE requirements, there isn’t a code issue, but it’s good to be aware that the language surrounding PPE levels is variable while the incident energy is consistent.
I Ensure arc flash labeling includes the incident energy.
I If site-specific PPE levels are used, have definitions posted in the electric rooms or by the electrical PPE storage.
Bus Configurations and Live Work
The introduction of bus configurations, based on experimental data and left open to interpretation, is the largest change to arc flash standards in terms of impact on the incident energy. It can be confusing because multiple configurations are often present in a single piece of gear. The configurations that apply to enclosed equipment are vertical conductors in metal box (VCB), vertical conductors with insulating barrier in metal box (VCBB), and horizontal electrodes in metal box (HCB).
When determining which configuration to use, you can generally consider VCB to be present in any equipment with a bus bar, VCBB to be present in any equipment which terminates in a breaker, and HCB to be present in any equipment with a bus bar that points at the opening. HCB is the highest hazard and is typically only applied to draw out switchgear. However, side panel access to MCCs also physically ends up with the bus bars pointed at the opening, so how the gear will be opened matters. Fortunately, the methods of approaching live work are fairly standardized, and the general practice of considering the VCB/VCBB worst case will apply to everything but a few edge cases.
I As part of the PJHA, determine if live work will be done through a standard gear opening or if the sides of the bus (i.e., opening the side panel on an MCC) will be exposed. If you will be outside the standard methods of gear access (front and back panels), consider carefully if live work is necessary.
NOTE: Most work falls under standard access and will be reflected correctly in the arc flash label. This recommendation is meant to ensure the work being done is not an edge case that may expose personnel to an elevated hazard.
If you have questions about how standard changes impact your facility, we’re ready to help. Call Interstates at 712-722-1662 to find expert assistance for all your arc flash needs.
Chris Myers, Project Engineer
This blog was originally published in the Current Connections Fall 2022 issue.