480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
(OP)
Working at a new facility that is using 480V 3-phase ungrounded distribution power to the MCC's. Not really seen this before.
So the new MCC we ordered has these ground indication lights.
One side of each light is wired to the ground. The other to the phase. So there is 480V across each of the three lights. If the phase it's connected to goes to ground this would cause both to be at the same potential and the light goes out. Right?
Is there anything new in technology to replace these? Is there any type of remote indication available for these that a burnout has occurred? Should there be warnings on the lights indicating they are not 120V?
Would appreciate anyone's experience with these kind of lights and known issues. Thanks!
So the new MCC we ordered has these ground indication lights.
One side of each light is wired to the ground. The other to the phase. So there is 480V across each of the three lights. If the phase it's connected to goes to ground this would cause both to be at the same potential and the light goes out. Right?
Is there anything new in technology to replace these? Is there any type of remote indication available for these that a burnout has occurred? Should there be warnings on the lights indicating they are not 120V?
Would appreciate anyone's experience with these kind of lights and known issues. Thanks!






RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
Yes, you can spend a lot more money on a Ground Dectection Relay that basically tells you the same info. The main advantage is if you have a network like Ethernet/IP, the GDR can any use it across the network. Many Feeder Protection Relays offer this function, so if you are using one anyway, just make sure it has this.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
However it is not the only means of ground detection. ... each ungrounded system load center also has a ground detection relay fed from PT's for alarm.
The lights are only a redundant/diverse indication.
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(2B)+(2B)' ?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
I have seen volt-meters used also.
The meters normally read 277 Volts. In the event of a ground fault one meter goes to zero volts and the other two meters go to 480 Volts.
Bill
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"Why not the best?"
Jimmy Carter
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
In the IEC market the push is to go to insulation monitoring systems. They inject a low frequency monitoring current and measure the system impedance to ground. They report the resistance and capacitance to earth. They are setup to alarm once the resistance drops below a set value. Here is one brand: vigilohm - Schneider Electric that is UL listed. In the IEC market they also use surge limiters that convert the system from ungrounded to grounded on over-voltage. This protects in case the transformer faults. However, I haven't seen any that are UL listed so they are out for use in the US.
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: 480V, 3ph, Ungrounded, GROUND INDICATION LIGHTS - is this the only way to detect?
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington