Corner Ground Delta

[electrofelon]

Interesting, show me a normal three phase wye power disconnect (with overcurrent device ) where the neutral ( grounded conductor )is switched with the ungrounded conductors. Show me a split phase ungrounded conductor (neutral) that in a normal situation is switched with the ungrounded conductors overcurrent device.

Thinking about it more, I realized that I do not understand your position. You point out that there are very few general applications where the neutral of a wye or split phase circuit is switched and/or has an over current device in it. I am not sure if you are making a point about something and what that has to do with the issue of switching or having an OCPD in a corner grounded grounded conductor.

 

[pipe_bender]

Thinking about it more, I realized that I do not understand your position. You point out that there are very few general applications where the neutral of a wye or split phase circuit is switched and/or has an over current device in it. I am not sure if you are making a point about something and what that has to do with the issue of switching or having an OCPD in a corner grounded grounded conductor.

I am stating the obvious but I did not see this mentioned earlier in a wye or split phase system if you open the neutral and not the other phases bad things will happen as your L-N voltages will be all over the place, if you have a corner grounded system and just open the grounded phase the other two phases will keep running normally, a 3-phase motor might even continue to run.

Arc Flash calculations are based on 3-phase Line-Line-Line bolted faults.
The presence or absence of a neutral does not come into the equation.

Are you saying for any given size transformer bank with three equal kVA transformers, say three 100kVA pole mount, the Incident energy contribution would be the same in a 480V corner grounded delta as a conventional 480/277 wye?.
Would all the required PPE / approach boundaries be the same?

 

[jim dungar]

Are you saying for any given size transformer bank with three equal kVA transformers, say three 100kVA pole mount, the Incident energy contribution would be the same in a 480V corner grounded delta as a conventional 480/277 wye?.
Would all the required PPE / approach boundaries be the same?

Yes.

The presence or absence of a neutral impacts the probability of a 3-phase fault occurring. Quite commonly a L-N arcing fault will be cleared before it escalates into a 3-phase fault.