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#16629 - 11/13/02 08:06 PM differnt voltage
doc Offline
Member

Registered: 11/25/00
Posts: 119
Loc: Texas
have a 277/480 3 phase panel feeding a 280 delta 208Y /120 volt transformer which then hooks to a 208/120 3phase panle.
Now across the legs I get 199-200 volts
line to ground I get 1 leg 139 volt 2leg 71 volt 3 leg 150 volt line to neutral I get 115 volts on each leg ,from neutral to ground get 50 volts .If I try to run a neutral wire in conduit it will arc any ideas on why the voltgae is off and why I have it on my neutral
any help appreciated
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#16630 - 11/13/02 09:06 PM Re: differnt voltage
caselec Offline
Member

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
It sounds to me that your transformer is not grounded properly. The voltages from phase to ground should be the same as phase to XO (neutral). The secondary voltages look pretty good phase to phase and phase to X0. There are a little low but your primary voltage is probably a little low. Take a look at 250.30

Curt
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#16631 - 11/13/02 09:31 PM Re: differnt voltage
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Doc,

Could you expand a bit more on this situation?

Are you seeing this at the sub panel?
How far away is the panel from the transformer?
Can you verify the system's grounding?
What loads are on during tests?
Are the loads on the branch circuits connected incorrectly?

TIA!

Scott s.e.t.
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#16632 - 11/13/02 11:18 PM Re: differnt voltage
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Doc! Welcome back, long time no see!

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#16633 - 11/14/02 04:37 AM Re: differnt voltage
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
I'm with caselec.
Probably an improperly bonded/grounded XO. Start there.


[This message has been edited by Redsy (edited 11-14-2002).]

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#16634 - 11/14/02 02:01 PM Re: differnt voltage
bobc Offline
Member

Registered: 02/05/02
Posts: 11
Loc: houston tx
Doc,havent made it out to your site but will try.The 3phase 480/277 bank is this an overhead bank?if supplied from poco is it a three or wire system,i agree with rest of forum there is a voltage inbalance verify grounding on 480 y bank and on 208y bank please keep us up to speed on this one.

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#16635 - 11/14/02 02:11 PM Re: differnt voltage
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
hi doc,
yeah, arcing noodles make for said assumptions....

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#16636 - 11/14/02 03:41 PM Re: differnt voltage
doc Offline
Member

Registered: 11/25/00
Posts: 119
Loc: Texas
ok first off one of these day I will work some place where all the wiring is correct but till then to expand a little.
There are 2 480 volt panels 3 ft from them is the trans and about 3 ft from it is the 2 panels that are 120/208 there is very little power being used out of these panels,no I have not verified that there is even a ground in the system other than the conduit that all the wire is running through
The other thing that gets me is even if I go to an outlet and test it or to abreaker for that matter I will get the same 50 volts to ground 139 ground to hot and yet 115 from hot to grounded conductor{neutral }.
If there is no ground can I just drive a rod down by the trans and ground it or do I need to run one back to the serviceanother thing would it make a difference if it is a subpanel feeding the trans again I am not sure.
oh last we have equipment that has been running for months on that 71 volt line
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