I AM A CONTRACTOR SALES REP. ONE OF MY CUSTOMERS HAS ASKED ME TO PROVIDE A SOLUTION FOR THIS APPLICATION. HE WANTS INDICATION LIGHTS SO HE CAN TELL IF ONE OF THE LEGS GOES TO GROUND, BUT DOESN'T WANT THE SYSTEM TO SHUT DOWN WHEN THIS OCCURS. DOES ANYONE HAVE ANY SUGGESTIONS AS TO WHO MAKES SOMETHING LIKE THIS?
GROUND FAULT INDICATION FOR 480V UNGROUNDED DELTA SYSTEM
- Thread starter bbbowen
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Re: GROUND FAULT INDICATION FOR 480V UNGROUNDED DELTA SYSTEM
Actually an old-fashioned electrical system, but there are still plenty of them around. It has always been a good design practice to install ground detection lights on this type system, but do not think it has ever been an NEC requirement.
Basic parts of system are usually:
(3) small 480-120V. xfmrs connected wye primary - wye secondary, (3) standard 120V. xfmr-type pilot lights with clear or white lenses, & a test pushbutton for testing the pilot lights.
There are variations of course, including using full size medium base incandescent lamps.
The assembly can be built-up, but believe that some companies like G.E./Yokogama, etc. that still sell 4-1/2" analog meters, offer these in a package.
A true 480V. 3-phase 3-wire ungrounded delta system does not "shut down" if one leg goes to ground. This was one of the reasons for the older popularity of this system, mainly in industrial applications. I think most now consider it less desirable than a solidly grounded 480/277 wye for most applications.
Actually an old-fashioned electrical system, but there are still plenty of them around. It has always been a good design practice to install ground detection lights on this type system, but do not think it has ever been an NEC requirement.
Basic parts of system are usually:
(3) small 480-120V. xfmrs connected wye primary - wye secondary, (3) standard 120V. xfmr-type pilot lights with clear or white lenses, & a test pushbutton for testing the pilot lights.
There are variations of course, including using full size medium base incandescent lamps.
The assembly can be built-up, but believe that some companies like G.E./Yokogama, etc. that still sell 4-1/2" analog meters, offer these in a package.
A true 480V. 3-phase 3-wire ungrounded delta system does not "shut down" if one leg goes to ground. This was one of the reasons for the older popularity of this system, mainly in industrial applications. I think most now consider it less desirable than a solidly grounded 480/277 wye for most applications.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: GROUND FAULT INDICATION FOR 480V UNGROUNDED DELTA SYSTEM
You can get Ul Listed ones from Erickson Electrical Equipment. They are in the accessories section.
[ October 20, 2004, 09:47 PM: Message edited by: jim dungar ]
You can get Ul Listed ones from Erickson Electrical Equipment. They are in the accessories section.
[ October 20, 2004, 09:47 PM: Message edited by: jim dungar ]
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
Re: GROUND FAULT INDICATION FOR 480V UNGROUNDED DELTA SYSTEM
We occassionally have a spec that says we have to provide ground detection. I will have to remember the package Jim pointed out. much nicer then building it up yourself.
The last one I did I remember testing it with the installing electrician. He was very leery when I put an alligator clip between a hot leg and the ground bar and then closed the main disconnect. Even when the first one did not explode (or whatever he thought might happen) he was still visibly nervous as I tested the ground fault indication on each leg.
Its probably true for many cases but most industrial plants are very leery of having the whole place shut down because of a ground fault. Most of the plants I put equipment in have ungrounded delta.
We occassionally have a spec that says we have to provide ground detection. I will have to remember the package Jim pointed out. much nicer then building it up yourself.
The last one I did I remember testing it with the installing electrician. He was very leery when I put an alligator clip between a hot leg and the ground bar and then closed the main disconnect. Even when the first one did not explode (or whatever he thought might happen) he was still visibly nervous as I tested the ground fault indication on each leg.
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