Test Set Up

If you've never seen a test set up - this is one from a few weeks ago. It was for single phase arc flash testing.

The copper bus bars are to establish a 1 inch gap at the back of the enclosure. The calorimters are up front. This was a 30 kA bolted fault at 480V/277.

We could not get this single phase event to sustain so it produced an incident energy that was Category 0 mosty because of the duration but the sound pressure and UV light was still very dangerous - we looked away from the light - there could be some serious eye injury - and it was technically a "non-event" I wouldn't want to be in front of it.

Unfortunately, the testing I am involved with is proprietary.

It was a 500 kVA enclosure only. I was testing a new design for a manufacturer where the top and side of the enclosure open up. The open design has quite an effect on the incident energy by allowing it to dispurse in multiple directions instead of at the worker. (similar effect as arc in air vs. arc in a box) Here is the follow up paper about it:

Open Design Pad Mount Enclosure

I guess ingnorance is bliss (and more comfortable) until something goes wrong.

Yes - the results in the paper were three phase.

However, the initial testing began with single phase events at the client's request. I knew this would go nowhere quickly because like you would suspect, the arc did not sustain. I think the longest duration was 1 or 2 cycles and this was at 30 kA bolted (calibration current) with a 1 inch gap at 480 Volts. Some copper bussing was used to "force" a 1 inch gap.

After several uneventful single phase arc flash attempts, I moved them to the three phase set up which was much more impressive.

I know a 1 inch gap is not realistic for a pad mount but the goal was to compare the incident energy with the cabinet in the open configuration and the cabinet in the closed configuration.

The client wanted the clearing time based on their typical primary fuse operation for the fault current that was used. This lead to 13 cycles based on the fault current and TCC of the fuse. I am not sure 13 cycles is realistic in many applications considering the size of many fuses that are used but we set the breaker to trip at 13 cycles. I believe the three phase arc would have sustained longer if we had the breaker set longer. The single phase tests would not sustain.

Again however, we were attempting to measure the difference between the open and closed configuration of the enclosure. Not quite the same objectives as EPRI and PGE.