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I don't know where they have come up with this. They do say not to exceed five minutes on the test, not five minutes. I would limit the testing to around one minute to avoid possible damage.

I believe you are playing word games with a translation. “is a structure designed for installation of cables” this would be my definition of cable tray. I am not clear what size cable is? 16mm^2 (>#6) or 48mm^2 (>#1) or are you talking about a multi-conductor cable (>3 conductors or >16mm^2...

If the use falls under the definition of “Premises” wiring I would say that 250.20 (b) (1) would prohibit the use of transformer. If not then 250.21 applies and grounding is optional. If choosing to go the ungrounded route, I believe that fuses are out of the picture as they operate...

That was not the greatest explanation, as I could see someone reading a potential on both legs and thinking they were both “hot” legs. All there is before connection is an unreferenced difference in potential. How this appears on a meter, (measured to ground)if the primary side is connected...

nwong16 "There seems to be so much debate about grounding a hot leg here at my company. Does anyone else have additional input regarding groudning the hot leg of a 230VAC secondary of a tranformer." I think the problem is that there is no “Hot leg” or “Neutral leg” until one leg is connected...

I work in the transmission line and substation world (in Colorado and surrounding) and we typically place arrestors where the lines enter the station, high and low side of transformers and all feeder exits. I have not seen an instance where they were distribed on a line.

SilverArc What you have done is the infinite bus method, it is only a good first estimate. In most cases it will give you an upper limit on the non-source side of the transformer. I use it to start my grid design while waiting for information. The maximum fault current depends on the strength...

If you need a number, for some preliminary calculations, I recently was given a quote on an identical transformer with an X/R around 27. are you working on a project in san deigo?

jghrist "I'm not sure exactly why more current flows into the earth from the edges of the station. I like to think of it as the current having more freedom to move out towards remote earth from the edges than crammed into the center, but I'm not sure that this is a valid explanation." More...