This week's question is purely hypothetical. The existing IEEE 1584 model is for three phase arc flash calculations only. The new version of IEEE 1584 (a couple of years away yet) will also only be for three phase arc flash calculations.

Here is this week's hypothetical question:

If a single phase IEEE arc flash model was available, would you have any use for it?
-Yes
-No

I'd say yes to both, but...

This question has multiple answers that depend on equipment types that might be more beneficial:
Equipment rated 50-250 VAC....not sure we need to quantify the type of equipment.
Overhead power lines and similar "open" systems where 3-phase faults are difficulty or impossible.
Enclosed single phase systems such as metalclad gear where propagation to other phases does is very unlikely.
High voltage (>69 kV) systems including precipitators.

Methinks that the first category might turn into more of a question of the onset of a self-sustaining arcing fault. Types 2 and 3 are basically extensions of the 3 phase cases. Type 4 is less common but found in a lot of industrial equipment which is exceedingly high voltage but very little no current.

I'd be really, really curious about the results on single phase equipment such as metalclad gear anyways. It has long been touted as being much safer than metal enclosed switchgear. However it is also a royal pain to properly PM and I can't honestly say with most of it that a proper inspection let alone a cleaning can ever be done. Given that with 1584 I have to treat it the same (and some of the test results seem to allude to this) it seems that metalclad switchgear is vastly overblown and simply not worth the substantially extra money for it, but it sure would be nice to see actual arcing test results that confirm this.

If SKM were to offer single phase arc flash evaluation, I would extend the model to some single phase items. However, it isn't really necessary and, for my present usage, I would consider this more a nice to have than a need to have item.

The NFPA 70E-2012 (130.5) requirement for field marking of equipment labels does not really provide an exception for 1PH equipment. It does allow you to use the tables, but the table parameters are such that there is alot not covered. So to be in compliance with that standard, we really need the tools to develop arcing energy and incident energy.

We can definitely say there can be an arc flash event on single phase panelboards & other single phase equipment. The question of whether the arc is sustained would go to defining the clearing time. If the arc cannot be sustained & it extinguishes itself presumably at the zero crossing, then wouldn't t<0.5cy, but only if the cause of the arc is cleared (melted or blasted away). This would usually result in a PPE Level of 0 or 1. But if the arc can be sustained, then using the IEEE 1584 equations, the energy can get pretty high, quite often PPE Level 3.

I've often wondered if a 1 phase equation were developed, if it would differ from the 3PH equations by a factor 1.732 someplace. I haven't researched the technical journals to see if there is a working theoretical or empirical formula out there for it.

SKM can perform 1-phase short-circuit calculations. They refuse to extend arc flash calculations to 1-phase equipment until there is standard in place. Understandable position.

The whole notion of only looking at 3 phase short-circuits as the basis of arc flash calculations needs to be re-evaluated. I find sometimes 3PH SC's aren't the highest available fault, often enough to ask why aren't we looking at LLG or SLG faults.

Then there is the whole part of the process where you're looking for switching scenarios that lower the available SC to see if breakers drop below the instantaneous range, thus increasing clearing time, thus increasing incident energy. Again, why are we only looking at 3PH SC's if we're doing that. The least likely arcing event will be a 3PH event whereas a LL, LLG, or SLG event are more likely.

I think if there is a standard then it will be mandatory to use it, so yes I would have a use for it.

I don't see a need for this in most cases. I believe it is assumed that a 1 phase arc flash could escalate to a three phase arc flash. I doubt if a single phase at 120 v would sustain unless there was a lot of current. It would be interesting to know more about whether it would escalate and under what conditions.

I am curious about what conditions/cases people think they might use a single phase arc flash model?

How about on actual single phase circuits?

I am presently working on a project for an elementary school. Service is 208Y/120 3Ph 4W 800A, which is an upgrade from the original 240/120 3P 4W. All of the branch circuit panelboards, serving the classrooms, are now 120/208 1Ph 3W.