wiigelec
Member
- Location
- Red Desert
Anyone test their high impedance ground system by connecting the load side of a spare bucket to the MCC grounding lug then closing in the breaker?
Anyone test their high impedance ground system by connecting the load side of a spare bucket to the MCC grounding lug then closing in the breaker?
Actually when I saw this in our maintenance plan I thought it was absurd, but if others are doing the same thing...
I just wouldn't do it the way you described in the original post. We had a ground fault detection system fail a few months ago because a PT fried. Of course we had a ground fault and nobody noticed for who knows how long because the only thing people were looking at was the idiot light and ignoring the ground fault ammeter. We have changed our rounds procedures to look at both the idiot light and the ammeter. Personally I would not want to induce a ground fault as part of a regular maintenance procedure since there are other ways to determine if the detection system is working provided it was designed properly. Newer substations have built in test functions if you order them that way. I just finished commissioning a new Eaton substation with a built in test function and the pulser function that ice described.
Actually when I saw this in our maintenance plan I thought it was absurd, but if others are doing the same thing...
I wouldn't either. Commissioning - yes. And, possibly some troubleshooting shooting scenerios - yes. But not for a regular PM.... Personally I would not want to induce a ground fault as part of a regular maintenance procedure ...
I don't think I have ever seen an HRG installation that didn't have test functions (However, I'm sure someone, somewhere has been or is being dumb enough to do that) .... Newer substations have built in test functions if you order them that way. I just finished commissioning a new Eaton substation with a built in test function and the pulser function that ice described.
Most installations I have seen are 58 ohm, 5A continuous resistors. The pulser shorts out half of the resistor. Fault current goes from 5A to 10A - maybe 2 sec ON, 2 sec OFF. No automatic start on the pulser - Acutuated with a front panel test switch. With one fault, systems will stay energized forever. And they should. That is the whole point of a 480Y HRG system.... GE (and others) use a system that locates the ground by pulsing ground currrent by changing the ground resistance slightly. This is done when a ground is detected. The system is usually timed, you have time to find and isolate the fault, if your to slow the system shuts down. ...]
This is the one part of the system that has not changed at least as far back as 60s installations. They still function the same, and they even look the same. I bought one a few years ago and it looked exactly like the ones that came with the 60s installs.... Ge supplies a pulse detector that lets you find and isolate the fault. ...]
The Eaton Medium Voltage HRG test functions only check the health of the control/pulsing circuit, not the detection circuit. A horn could be added to back up the idiot light.
I don't think I have ever seen an HRG installation that didn't have test functions (However, I'm sure someone, somewhere has been or is being dumb enough to do that) .ice
... I don't think I have ever seen an HRG installation that didn't have test functions (However, I'm sure someone, somewhere has been or is being dumb enough to do that). ...
Interesting.... I guess we were dumb enough to do that, none of our older installations have test functions built-in.
What exactly is the "old fasion way" of testing/... That test switch wasn't covered very well in the documentation we recieved so we tested it the old fashion way. ...
Interesting.
First I would say careful with the "we". I've read a lot of your posts and I highly suspect, "you" were not part of the "we" that decided not to put in any test functions.
Second:
No test functions at all? really? No pulser shorting out part of the grounding resistor? No alarm relay across the grounding resistor? Not even phase to ground lights?
Yuk. You got really unluckly inheriting that thing.
ice
What exactly is the "old fasion way" of testing/
ice