Service 480v 3ph or straight 480 ?

[Hv&Lv]

Does anyone have a schematic of this type of 480v grounded or ungrounded system ?
it only has 480 line to line no low voltage at all

This schematic is all over the web.
Can you check the voltages with the disconnects open, no load? See the readings for yourself? Sitting here, I can't understand why one said the pot is bad and the other said it is good, unless one checked it under load, and the other checked it without load. Besides, in order to correctly check the pots, they need to be seperated.

 

[Part-Time]

Does anyone have a schematic of this type of 480v grounded or ungrounded system ?
it only has 480 line to line no low voltage at all

so i should get 480 to ground right ?

 

[Hv&Lv]

Does anyone have a schematic of this type of 480v grounded or ungrounded system ?
it only has 480 line to line no low voltage at all

Note the voltage after the GES and the GEC

 

[Part-Time]

i was told an Electrician that is 40 years my senior that it is an ungrounded 480v Delta
that was used to supply refinery type plants and that trying to read to ground would give me
incorrect voltages to ground this is normal for this system he said and not a common system any more, most have been replaced
to 480/277 i will take his answer as truth since he has worked on this type before and took the time to educate me,

 

[Part-Time]

i was told by an Electrician that is 40 years my senior that it is an ungrounded 480v Delta
that was used to supply refinery type plants and that trying to read to ground would give me
incorrect voltages to ground this is normal for this system he said and not a common system any more, most have been replaced
to 480/277 i will take his answer as truth since he has worked on this type before and took the time to educate me,

 

[texie]

Is it possible that the OP has an ungrounded system at his end that was originally fed from an ungrounded 480 delta POCO bank and at some point the bank was changed to a 480Y grounded bank? Maybe it just worked and now a ground fault has developed on his end and since it is not solidly grounded at his end he gets strange readings. Just a thought-I have not thought this all the way through and, of course, we may be missing some critical info here.

 

[ptonsparky]

Sounds like an ungrounded delta if the POCO is telling him no low voltage, ie 277v. There should be a set of lights at the service entrance to indicate when one oc the phase goes to ground. I have only seen one of those systems and it has been at least 25 years ago.

 

[iceworm]

i was told an Electrician that is 40 years my senior that it is an ungrounded 480v Delta that was used to supply refinery type plants and that trying to read to ground would give me incorrect voltages ...

Yeah that was my thought.

... I didn't see any failure modes that would give 510, or 484 to neutral/ground. ...

...An un-grounded delta can - but this ain't that. ...

Or an un-grounded bank.

I guess the neutral and ground are not:

Neutral and ground bonded at service.

So now you can go look for something else taking out your control transformers.

ice