Hi folks,

I am new to this board and relatively new to arc flash studies so I was hoping some of you might have some opinions on one of the assumptions I am using in CYME Arc Flash Hazards module - Industrial Analysis. Hopefully there's a few CYME experts on here. I'm looking to get arc flash levels for the LV side of the padmount and the assumptions I am using are as follows:

Method: IEEE-1584
Bus gap: user defined based on measurements
Working distance: 18 inches (glove length)
Connected Equipment Type: Open air

It's the last one, Connected Equipment Type, that worries me -- I originally thought "Open air" because the padmount transformer is outdoor so that made more sense to me than "Switchgear" since switchgear is indoor and also deeper. The options in CYME are "Open Air", "Cable", "Switchgear", or "MCC/Panel". None of these seem 100% suited to my Padmount LV application, but the more I think about it the more I think open air probably isn't right because we'd want to account for reflection off the back of the padmount as well as off the ground. What do you guys think? Now I'm kind of leaning towards MCC/Panel but that doesn't seem 100% right either. I appreciate your advice for this arc flash newbie! Thanks

NKH

Open Air would imply that there is no enclosure which is not the case, so some sort of enclosure is needed. I am not sure with Cyme but the new version of EasyPower released in Jan for the new IEEE 1584-2018 equations allows the actual enclosure dimensions to be used. Perhaps Cyme has the same thing to support IEEE 1584-2018. Are you using the latest Cyme version?

Another option is to use the table from NESC to determine the incident energy as that was based actual testing results and I believe it is 4 cal/cm2 but not in my office this week so can't look it up.

Thanks for your response. I posted my question on CYME forums as well and they said that their Open Air option in the drop down is based on the idea that the energy is dispersed in 5 directions (all directions except the floor). Unfortunately CYME is not updated to IEEE-2018 yet and they said they expect that to happen in late 2019.

With my padmount because it is pretty shallow it's almost like the energy is dispersing in 4 directions so I don't see the results being as conservative as a switchgear, but it does look like I've reached the limit in what I can do in CYME. I'll have to see what other options my company has available. I agree using actual enclosure dimensions would be best. Thanks,

NKH

SKM has new release with options for enclosure type (dimensions) and electrode configurations according to IEEE 1584 2018.

I am also a CYME user among other products. The LV side of the padmount transformer would be classified as a "Switchgear". It is inside a box at this location.

Thanks everyone for your feedback I will use Switchgear in CYME for my padmounts, for now. Going forward I'm hoping CYME will update to 1584-2018 and I can use HOA. Can't wait to see these software updates...

I believe the IEEE1584-2002 designations of Switchgear and MCC/PNL had more to do with default bus bar spacing and working depth than they didwith enclosure sizing.
If you are 'overriding' the default values, it doesn't matter what choice you start with. If you use default values then I agree switchgear makes more sense.