Corner Ground Delta

Rjryan said:
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.
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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.
 
electrofelon said:
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.
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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.
jim dungar said:
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.
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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?
 
pipe_bender said:
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?
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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.
 
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