ScarletPmprnckle
Member
Do the metallic non-current carrying parts of a corner grounded delta system become energized. Since one phase is grounded, therefore being the same potential? Just curious. Thank you if anyone can help.
Corner grounded systems
- Thread starter ScarletPmprnckle
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ericsherman37
Senior Member
- Location
- Oregon Coast
Energized with respect to what? To ground? It's grounded already - same potential.
- Location
- Illinois
- Occupation
- retired electrician
It works the same way as the standard 120/240 volt single phase system. The only potential to ground, from the grounded conductor, on either system, assuming normal conditions, is the voltage drop on the grounded conductor.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Scarlet, welcome to the forum! :smile:
We could intentionally ground any single conductor of a supply, and every other system conductor would measure to earth whatever the voltage difference is between the intentionally-grounded conductor and the other conductor.
If we grounded, for example, one end of a 120/240v secondary, we'd have one conductor that is 120v to earth and one conductor that is 240v to earth. That grounded conductor would behave exactly the same as the center tap we usually ground.
As mentioned above, a grounded conductor is the same in any system, whether it's a center tap or a phase condcutor. The only reason a hot conductor measures hot relative to earth is because we intentionally ground another system conductor.
We could intentionally ground any single conductor of a supply, and every other system conductor would measure to earth whatever the voltage difference is between the intentionally-grounded conductor and the other conductor.
If we grounded, for example, one end of a 120/240v secondary, we'd have one conductor that is 120v to earth and one conductor that is 240v to earth. That grounded conductor would behave exactly the same as the center tap we usually ground.
ScarletPmprnckle
Member
Thank you, that makes sense. What about if you put one one of those little voltage sensors next to the panel can. Would it sense voltage?
ericsherman37
Senior Member
- Location
- Oregon Coast
Those things will sense voltage in the middle of a cow pasture. But for some reason they won't when you stick them in a live plug...
But no, if your panel can is properly grounded and all that, blah blah blah, there should be no voltage to ground on the metal enclosure. That is a dangerous situation as we all know.
Think of it this way... a standard 240/120V residential service utilizes a single phase transformer. The secondary has a tap on one end of the winding, another tap on the other end of the winding 240 volts away, and then there's a tap right in the middle of the winding, 120 volts away from each end. Usually the center tap is grounded. But otherwise, it's still a direct tap off an energized transformer winding isn't it? But when it is referenced to ground it has the same potential as ground, therefore no voltage between neutral and ground.
The corner ground thing is the same deal just in a different configuration (and a different transformer of course). But imagine taking the grounded center tap off the residential service transformer and just moving it to the end of the winding. If it remains grounded it's not going to magically become energized with respect to ground when it's moved. All it means for the residential service is that you wouldn't be able to use 120V anything.
Grounding a phase of a corner-grounded delta system is simply going to reference that phase to ground. You bond all your metal stuff, you install a grounding electrode system which will (among other things) help keep the ground reference stable with respect to the planet, and so forth. The only difference is that you're grounding the end of a transformer winding instead of the middle of it.
ScarletPmprnckle
Member
Thank you, that was a good explanation.
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