# Ground on 600 volt delta



## sparky105 (Sep 29, 2009)

I finished a RTU service upgrade today turned on my 60 amp disco for 600/208 y tranny and I was testing across the 600 volt taps and found 600 phase to phase all 3. I went to ground and got 23 v a phase, 600 b phase and 610 c phase. went down to the main splitter same thing. went to the main MCC expecting to find a ground light out on the system but all 3 lights were lit.

We call the in house electrican to get some history and find out if he wanted to continue trouble shooting and he told us it was found about 3 yrs ago and that the supervision didn't see the issue being serious enough to shut down the building for.:blink:

I was wondering who has had experience with a 13800 y / 600 volt delta system with a phase going to ground I have not seen this only heard about it because our local poco did away with delta secondaries before my time. How much damage is to be expected when sometime like this goes off.


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## BuzzKill (Oct 27, 2008)

search for "grounded delta" on here.


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## sparky105 (Sep 29, 2009)

BuzzKill said:


> search for "grounded delta" on here.


its an ungrounded delta secondary 
with a ground showing on a phase


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## BuzzKill (Oct 27, 2008)

sparky105 said:


> its an ungrounded delta secondary
> with a ground showing on a phase


oops....


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## sparky105 (Sep 29, 2009)

That's what we thought but they said go ahead commission your rtu and we'll see to it I was just curious if any one had seen one go boom? I do understand how hard they are to find. Just haven't had alot of experience with this type of issue.


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## Big John (May 23, 2010)

sparky105 said:


> ...It was found about 3 yrs ago and that the supervision didn't see the issue being serious enough to shut down the building for.:blink:


 Yeah, I guess it's better for them to wait until a second fault dumps their building in the middle of the day and causes thousands worth of damage before repairing it? :no:


> How much damage is to be expected when sometime like this goes off.


 That depends on where it happens in the system. If it happens on the load side of your 60 amp disco, then they replace some conductors and replace some fuses.

But we had an arcing ground fault on an ungrounded 600V delta that did a tremendous amount of damage. It caused multiple failures throughout several pieces of cable and wiped out two 15HP motors. It was all old equipment, so the insulation definitely wasn't the greatest, which accounts for a lot of that, but I wouldn't want to try that on a new system, either.


> ...Went to the main MCC expecting to find a ground light out on the system but all 3 lights were lit.


 That doesn't make any sense. I'd check the voltage on those lights to see if it matched what you had in your system.

-John


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## sparky105 (Sep 29, 2009)

B That doesn't make any sense. I'd check the voltage on those lights to see if it matched what you had in your system.
-John[/quote said:


> I agree but they are not letting us in it's an in house deal I just hope no one gets hung up on 600 to ground that would be a bad day


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