230V Delta?

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PetrosA

PetrosA

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Location
Lancaster, Pennsylvania
I've been trying to wrap my head around a system I recently worked on in an old factory in York, PA. It's a 230V high-leg Delta system from what the on-site electrician explained, but the readings are unlike anything I've ever seen and I'm trying to figure out what's going on. There are three hots and a ground on site, no neutral. Phases A and C read 137V to ground, while phase B reads 157V to ground. Between any phases I get 248V. The open knife switches make it really interesting ;) PXL_20210222_200551344.SMALL.jpg
 
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__dan

Senior Member
I don't have a reference for it but I recall reading that exposed busbar is not grandfathered and an OSHA violation.

Voltage to ground readings will have no meaning if the system is floating. The only way to be sure of this is to look at the source transformer nameplate for available windings and then open it up to see if there is or is not a main or system bonding jumper.
 
drcampbell

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Registered Professional Engineer
Without a neutral, it's not a high-leg system, just a symmetrical 3-phase circuit. Phase B can't be "high" by itself; it can only be high with respect to something. If you needed 208v, where would you connect the return conductor?
(that's not to say that the transformer supplying it isn't configured as a high-leg delta, or that a neutral couldn't be brought out)


__dan said:
... exposed busbar is not grandfathered and an OSHA violation. ...
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path to an electricians heart-text-320x180.jpeg
 
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Frank DuVal

Senior Member
Location
Fredericksburg, VA 21 Hours from Winged Horses wi
Occupation
Electrical Contractor, Electrical Engineer
Just what does the sign under the lamps say?

Anytime I see three lamps I think of paralleling a generator hot. But I highly doubt this is the case here.

I was once in an old substation that was out of service and saw one of those open knife switch panels, several wires removed, sticking out randomly. Reached over and closed one of the knife switches. The lights in the room came on! Hmm, not everything is out of service.... :unsure:

An early lesson in never trust anything to be safe, test, test, test.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Worked on a few of those in my life.
Interesting that there are arc-flash warning stickers... seems the least of one's concern :)
What is the creature above the meter.?. that I have not ever seen !
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
PetrosA said:
Considering that there are only three sets of feeders going into that building, I'm going to go with ptonsparky's theory that this is an non-ground referenced Delta system.
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Yeah I agree. Regarding what you said you were told in the OP, It's interesting how few people seem to understand the difference between open vs closed Delta, high leg Delta, and grounded/ ungrounded Delta. You can theoretically have all 8 combinations. Many mix-up or interchange these terms. I worked on a 600v ungrounded Delta once. The other electrician kept calling it an "open Delta" (it was in fact a closed Delta).
 
Dsg319

Dsg319

Senior Member
Location
West Virginia
Occupation
Wv Master “lectrician”
ptonsparky said:
I believe that is why your voltage to ‘ground‘ is all over the place. It has no reference until something faults. The first fault should light one or more lamps. I’ve only worked with one or two. Forty years ago, plus or minus.
The smart guys will have to step in.
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What is causing the voltage readings to ground if there isn’t any known faults. Phantom voltage with high impedance meter?
 
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