Utility Xfmers

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FaradayFF

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Greetings, Sparkies!

Are utility distribution transformers grounded at the green box? We're talking delta-wye, 12kV to 480V. Is there ground rod under the box or is the neutral grounded at the service panel(or MCC)?

Thank you,
EE
 
Yes pretty much always. The primary and secondary grounded conductors (if they exist) will be connected to the transformer case (that connection may be internal in the transformer)and will be tied to rods.
 
FaradayFF said:
Greetings, Sparkies!

Are utility distribution transformers grounded at the green box? We're talking delta-wye, 12kV to 480V. Is there ground rod under the box or is the neutral grounded at the service panel(or MCC)?

Thank you,
EE
Click to expand...



Yes, the neutral is grounded with a ground rod, and interconnected to the utility neutral when fed via a multi grounded neutral system.
 
As far as I know, every POCO device is bonded to an electrode, either a rod or a pole basket, or boot, or whatever it's called.

Just about every pole has a #6 cu wire running into the earth; certainly every one with a transformer, switch, recloser, etc. on it.

I imagine that they have one or more driven electrodes under a pad-mounted transformer. The neutral is grounded everywhere.
 
Interesting. If the neutral conductor is also tied to service entrance ground rod(at MCC), then neutral wire is grounded to earth at two places. I gotta research that one..
 
FaradayFF said:
Interesting. If the neutral conductor is also tied to service entrance ground rod(at MCC), then neutral wire is grounded to earth at two places. I gotta research that one..
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Sometimes it's "grounded" at a whole lotta places (see "multi grounded neutral").

What does "grounded" mean here? I means connected to a grounding electrode, it does not imply a metallic path between the multiple connection points (although I suppose there could be one).

Is there a concern or just the quest for knowledge?
 
FaradayFF said:
If the neutral conductor is also tied to service entrance ground rod(at MCC), then neutral wire is grounded to earth at two places.
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As the earth is considered to not be conductive to rely on as a conductor, it is also considered to not be a parallel pathway for neutral currents.

That's related to why not having a metallic pathway between buildings when using a 3-wire feeder is part of the exception to the 4-wire rules.
 
I recently saw some graphics in a Mike Holt book that, along with the text, explained it very well. I’m not sure if I read this in the same book or not, but the neutral in the utility’s distribution system is grounded everywhere. In fact, the earth does conduct some of the current. I think I came across this while I was learning how a clamp-on ground resistance tester works... it was very interesting. I’d like to learn more about power distribution.
 
LPS said:
I recently saw some graphics in a Mike Holt book that, along with the text, explained it very well. I’m not sure if I read this in the same book or not, but the neutral in the utility’s distribution system is grounded everywhere. In fact, the earth does conduct some of the current. I think I came across this while I was learning how a clamp-on ground resistance tester works... it was very interesting. I’d like to learn more about power distribution.
Click to expand...

I'd argue the majority is through the water pipes, gas pipes and TELCO shields. The MGN is nothing more then a bonding jumper to let the current get to those.
 
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