480V service with no ground

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Jesse7623

Senior Member
Location
eastern Mass
I am on a farm replacing a service (120/240V)As I looked around the farm I discovered a 480V underground service in pvc.The service is earthed at the pole but no ground wire is run in the pipe.at the indoor transformer about 1/4 mile away thereis a ground rod.I think this is a pretty dangerous scenario as there is no way to clear a ground fault on the primary side of the transfomer.But maybe its not as bad as I am thinking.I would like some input in this matter.
thanks in advance,
 
Jesse7623 said:
I am on a farm replacing a service (120/240V)As I looked around the farm I discovered a 480V underground service in pvc.The service is earthed at the pole but no ground wire is run in the pipe.at the indoor transformer about 1/4 mile away thereis a ground rod.I think this is a pretty dangerous scenario as there is no way to clear a ground fault on the primary side of the transfomer.But maybe its not as bad as I am thinking.I would like some input in this matter.
thanks in advance,
Click to expand...

Is it 3? 4 wire?
 
I guess a key question would be is there a neutral at the transformer and is it bonded to that groud rod? (which adresses chris' answer)
 
480 no nuetral
1/0 copper
I am not there right now but my boss is.
I think he intends to get on this thread in a little while and explain a little more.
 
Jesse,

Sounds like a 250.21, ungrounded system. Sometimes farms will have a water pumping

system that an ungrounded system is ideal for. 250.24(E). Are you familiar with ungrounded

systems?
 
Jim W in Tampa said:
Without neutral i too see a problem. How would you clear a phase to case short ? No ground rod could do that.
Click to expand...
If it's a true "ungrounded system" (the transformer has no neutral) then phase to case short does not create a immediate concern... one reason for such systems.. there is monitoring required to detect such "leakage" as it poses a potential hazard. (SEE 250.21{B} )
 
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augie47 said:
If it's a true "ungrounded system" (the transformer has no neutral) then phase to case short does not create a immediate concern... one reason for such systems.. there is monitoring required to detect such "leakage" as it poses a potential hazard.
Click to expand...

That sucks, no 277 for my lights . Why would they do this ?
 
It's normally done to allow equipmemt to continue to operate even with a line to "ground" short. The monitor is there so such "shorts" can be fixed before a second phase goes to "ground" also (and for safety)
 
Jesse7623 said:
I am on a farm replacing a service (120/240V)As I looked around the farm I discovered a 480V underground service in pvc.The service is earthed at the pole but no ground wire is run in the pipe.at the indoor transformer about 1/4 mile away thereis a ground rod.I think this is a pretty dangerous scenario as there is no way to clear a ground fault on the primary side of the transfomer.But maybe its not as bad as I am thinking.I would like some input in this matter.
thanks in advance,
Click to expand...


My guess it that it was installed before the 2008 was adopted.
 
I vote for corner ground.

A couple years ago after an ice storm wiped out most of the center part NE some of those old systems were replaced with Wye transformer banks. It was up to the customer to update his underground to the wells. Hope yours doesn't fall into that category.
 
This would make sense

This would make sense

acrwc10 said:
Is this system a corner grounded delta ?
Click to expand...

Running a separate ground wire would be redundant if one of the legs are equal to ground. The question then is what to bond metal enclosures and raceways for the 480v equipment...
 
augie47 said:
If it's a true "ungrounded system" (the transformer has no neutral) then phase to case short does not create a immediate concern... one reason for such systems.. there is monitoring required to detect such "leakage" as it poses a potential hazard. (SEE 250.21{B} )
Click to expand...

I am not sure about whether it was for irragation pumps but as of now it is being used to power a packing house.and when I looked at the system it looked petty scary.Like I said earlier I am not there I am back east but my boss is there and he is going to get on the forum and make things a little clearer hopefully...
 
gmsoucy said:
i am trying to post....
Click to expand...

And you're doing a good job of it. :D

Your first few posts will need to be approved by a moderator before they will appear when you submit them

Roger
 
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