Arc flash hazard for single phase load

How do you evaluate single phase load in your arc flash study? Do you put labels on single phase panels? Thanks!

Is it too easy to answer?

You would have to use the 3 phase calculations which would be over kill. What voltage is the load? How much short circuit current is available? My experience has been to model to the panels, mcc's switchboards etc. and stop there. Perhaps other's have gone down to the single phase load level but I'm not sure it is necessary unless it is a huge load with a big breaker and lots of short circuit current. Plus, I'm not sure how you would do it with only three phase formulas.

Single Phase

As far as I know there is no method for calculating a single phase load to date. I do this method, label as CAT#0 PPE 4ft AF boundary with the correct voltage gloves (Shock protection) when working in the restrictive area.
Personaly, there are no right or wrong methods just set up a program go with it.

Single Phase Load calculations

You can calculate with ArcPro Software but check to see if the transformer meets the requirements of exclusion under IEEE 1584. LV single phase often will and you can use the Tables for PPE and labeling. Many folks are labeling even single phase panels. Others are only labeling 3-Phase.

For unqualified workers it is wise to put some kind of label on all panels.

I'm at a fairly large University/Medical Center in the midwest. I am using a software program by the name of "Volts" from Dolphin Software. We are labeling everything from 3 phase transformers to single phase 30 load centers at our medical center. The logic is the guy with the least amount of electrical experince will be resetting the breaker, that's the guy I'm trying to protect.

ETAP 7.0 (the latest version) does single phase arc flash calculations. See http://etap.com/downloads/ETAP_70_Brochure.pdf . Single phase arc flash is shown on page 3 under new features. I haven't had a chance to try it yet though.

Single Phase Load calculations

Don't know what ETAP is doing. SKM has added a calc which extrapolates the ArcPro Values from the NESC standard. Sweet way to do it but I don't know if the values hold up outside of the NESC table list. If you want them to be accurate you should use ArcPro directly. I think all the original IEEE work was on 3 phase but they did very little testing. I think around $60K of the $500K was on testing. Most is administrative overhead.

pressure relief

Hello sir/madam,

I am currently studying ARC flash in the panel and I have read that many panel builders provides Pressure relief to discharge the pressure, created during arc.

I want to know,

1. Is there any standard to design pressure releif?
2. How to decide area of opening for pressure relief.

Thanks
sanjeet

Single Phase

There are three solutions to the problem of single phase arc flash (Assuming that you are fed from a 240 volt source, or a 208 volt source with a transformer 125 kva or larger)
1) use the tables for 240 volt equipment and below. Beware though of the notes and limitations of that table.
2) calculate three phase, and divide by the square root of 3 (for 240 or 208 volt) or by 3 (for 120 volt). This could also be used for 480 volt systems.
3) take the position that sustained arc fault on a single phase source is not a practical concern, and label it a Cat 0.
Bear in mind, only 1 and 2 give you some level of technical backing. 3 may be reasonable and safe, but you are out on a limb.

Arc Flash Pressure Relief on Panelboards

To my knowledge the standards for panelboards don't provide for pressure relief sufficient to vent an arc away from a worker. The test methods for panelboards only cover bolted fault which has much less pressure than an arc fault.

Only the arc resistant standards have venting for worker protection in arcing fault. Take care when interpreting equipment tests and claims. The standards are really just catching up in the US on arc flash and equipment but the IEEE standards are starting to catch up.

Arc Resistant means something for arcing fault. Normal fault tests don't have much meaning.