240v 3 phase. Ungrounded service?

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Kg808

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Came across a type of service that I have never seen before. And was wondering if maybe before I assume something is damaged or calling the utility I would check in here to get some education.
I tested A to B:240v
A to C:240
B to C:240
A to ground: 240
B to geound: 0
C to ground: 240
3 wires coming from mast to utility transformer on pole.
Is this a standard 3 phase system? I’m assuming it’s 240 ungrounded.

Thanks!
 
That is either an ungrounded service with a ground fault on the B phase, or it's a corner-grounded delta where B is intentionally grounded. That's an unusual but legitimate service type. If it's corner-grounded, then the B phase is treated as a grounded conductor ("neutral") rather than a hot phase.
 
mpoulton said:
That is either an ungrounded service with a ground fault on the B phase, or it's a corner-grounded delta where B is intentionally grounded. That's an unusual but legitimate service type. If it's corner-grounded, then the B phase is treated as a grounded conductor ("neutral") rather than a hot phase.
Click to expand...

It's not a neutral. It's a grounded conductor. This is one case where they aren't the same.

It is supposed to be white (or grey).
 
mpoulton said:
That is either an ungrounded service with a ground fault on the B phase, or it's a corner-grounded delta where B is intentionally grounded. That's an unusual but legitimate service type. ...
Click to expand...

If it were an ungrounded delta service, there would need to be a ground monitoring system, and if the B phase is accidentally grounded, it would be in an alarm state.

Your choices in delta systems are either a corner grounded, or ungrounded, in which case it must have that ground monitoring system. Most likely it’s a purposely corner grounded system, that’s cheaper.
 
So this is awesome knowledge!
Now, knowing what to look for, I've done some research.
Heres the next question I cant seem to figure out..

I have a piece of 3 phase equipment a condenser rated at 208/230v. The customer needs this equipment hooked up and had it installed prior to me being on site. He was told by the building manager that he had 3 phase, which seems correct..

However, if one leg is grounded, can I still use this type of service for my equipment?

Also, yes, there is a 200A main breaker and it disconnects all 3 legs.

Thanks!
 
Agreed: yes. With rare exception, the equipment doesn't care about voltage to ground, only line-to-line.
 
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