Should the NEC ditch grounding electrodes?

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Dennis Alwon said:
I agree kwired the grounding electrode conductor especially to a rod is not very necessary, however there are many things in the nec that are not dangerous or urgent if left undone. If I have a strap or staple 2 inches beyond the nec requirementm no one is going to loose sleep over it but the code needs to have guidelines. To eliminate the grounding electrode conductor IMO, may not be the worst thing in the world but it does have some purpose and can help to some degree. Why would we eliminate it?
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In my instance it wasn't that I had no intention of connecting a GEC, it just had not been done yet when this inspector happened to show up. I didn't feel it was that important that it be done immediately, but he seemed to think I should have never even thought of energizing my new service equipment without an GES connected to it.

petersonra said:
I agree that the added level of safety, if any, is very limited, but I also think we have way too many grounding electrodes to go back and redo all of your electrical systems to come up with something better.

There have been some incremental improvements such as requiring 4 wires to go to outlying structures.

For those that think that an 800 foot service run creates some kind of issue, how is that any different than running a feeder underground from the main panel board for 800 feet to another structure. Don't you have the same potential voltage difference there between the two earth points?

And what about delta systems that have no earth reference at all? Are they somehow inherently unsafe now?
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Ungrounded systems still need to have all non current carrying metal objects bonded together to form an equipment grounding system as well as bond that to a grounding electrode system. The reasons are the same as they are for a grounded system - the need to have grounding electrodes may still be just as questionable, but we still need to bond non current carrying objects together whether we earth them or not.
 
mbrooke said:
That's actually how and why arc logic came about years before we saw it in homes. POCOs were the first to use "sensitive earth fault protection" which looks for the arcing signature of downed wires.
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See you took what I said and made it not funny.
I had absolutely nothing intellectual to add to the thread and it took me 20 min to come up with that,,,
Nope no partying with you EE or not.
 
kwired said:
In my instance it wasn't that I had no intention of connecting a GEC, it just had not been done yet when this inspector happened to show up. I didn't feel it was that important that it be done immediately, but he seemed to think I should have never even thought of energizing my new service equipment without an GES connected to it.

Ungrounded systems still need to have all non current carrying metal objects bonded together to form an equipment grounding system as well as bond that to a grounding electrode system. The reasons are the same as they are for a grounded system - the need to have grounding electrodes may still be just as questionable, but we still need to bond non current carrying objects together whether we earth them or not.
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For ground (earth) free systems I used DC injected in to the AC lines to monitor any possible stray ground fault on any of the lines. Without monitoring a ground fault could remain, not causing any problems until a second fault occurred on another line. The MPFC was 95KA, I didn?t fancy being around if it went bang. I?ve seen the aftermath of a line to line fault, it bit lumps out of 8x?? busbars.

As you say, the system was in grounded metallic containment. The above fault didn?t do the containment any favours.
 
electricalist said:
See you took what I said and made it not funny.
I had absolutely nothing intellectual to add to the thread and it took me 20 min to come up with that,,,
Nope no partying with you EE or not.
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But its true, even if meant as a joke (which I appreciate you making none the less). Because POCOs set zero sequence pickup values close to phase-to-phase values to handle neutral imbalance, downed conductors and broken insulators go unnoticed 1/3 of the time. I think we can all attest to seeing downed primaries smoking and arcing with fire trucks standing by waiting for POCO to disconnect the power. The solution to this has been reclosers and feeder relays with arcing signature analysis. Engineers have been working on this concept will before residential AFCIs came to be which I think speaks a lot.
 
Tony S said:
For ground (earth) free systems I used DC injected in to the AC lines to monitor any possible stray ground fault on any of the lines. Without monitoring a ground fault could remain, not causing any problems until a second fault occurred on another line. The MPFC was 95KA, I didn?t fancy being around if it went bang. I?ve seen the aftermath of a line to line fault, it bit lumps out of 8x?? busbars.

As you say, the system was in grounded metallic containment. The above fault didn?t do the containment any favours.
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I have a question. Are ground rods required in your codes? ;)
 
Tony S said:
For ground (earth) free systems I used DC injected in to the AC lines to monitor any possible stray ground fault on any of the lines. Without monitoring a ground fault could remain, not causing any problems until a second fault occurred on another line. The MPFC was 95KA, I didn?t fancy being around if it went bang. I?ve seen the aftermath of a line to line fault, it bit lumps out of 8x?? busbars.

As you say, the system was in grounded metallic containment. The above fault didn?t do the containment any favours.
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My situation was a 100 amp 120/240 grounded three phase service for a small pumping station. Utility transformer was pole mounted on a pole only 30 feet or so from my service disconnect and was an open delta composed of a couple of 10 or 15 KVA transformers. The pole did (or at least should have) had an electrode bonded to both primary and secondary circuit grounded conductors. I was not intending to leave this installation without a grounding electrode system - I just had not connected one yet when the inspector had arrived to the site - somewhat unexpected. My beef with him was that this temporarily missing electrode was not as critical as he seemed to think it was to overall safety of the system. Setting up additonal equipment to detect any fault to earth would have been much more time and expense then just driving a rod (or two) or bonding to the piping that eventually did get bonded as well because it also was a qualifying electrode.
 
mbrooke said:
I have a question. Are ground rods required in your codes? ;)
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Ground rods are only a requirement for TT supplies, that said there is no reason a rod can?t be included in other systems. A common situation would be where a TT supply is converted to PME (CNE), if the rod(s) are in place then it makes sense to use them.
For TN-S and TN-C-S it is the responsibility of the DNO (POCO) to maintain an effective earth. They?re famous for trying to avoiding their duty to maintain an effective earth.


kwired said:
My situation was a 100 amp 120/240 grounded three phase service for a small pumping station. Utility transformer was pole mounted on a pole only 30 feet or so from my service disconnect and was an open delta composed of a couple of 10 or 15 KVA transformers. The pole did (or at least should have) had an electrode bonded to both primary and secondary circuit grounded conductors. I was not intending to leave this installation without a grounding electrode system - I just had not connected one yet when the inspector had arrived to the site - somewhat unexpected. My beef with him was that this temporarily missing electrode was not as critical as he seemed to think it was to overall safety of the system. Setting up additonal equipment to detect any fault to earth would have been much more time and expense then just driving a rod (or two) or bonding to the piping that eventually did get bonded as well because it also was a qualifying electrode.
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Like others it seems to me someone was acting officiously without good reason.

My experience of pump houses, if the installed plant if correctly bonded will form a much better earth return than any rod.

The systems I was working on were for induction furnaces where due to the high currents involved the flexible cables had water pumped through them. This made it necessary to have a truly earth free system. We had an intermittent earth fault which when detected by the monitoring opened the 11KV OCB feeding the 2600KVA 660V transformer. It took me nearly three months to find the fault and that was down to pure luck.
 
Tony S said:
Ground rods are only a requirement for TT supplies, that said there is no reason a rod can?t be included in other systems. A common situation would be where a TT supply is converted to PME (CNE), if the rod(s) are in place then it makes sense to use them.
For TN-S and TN-C-S it is the responsibility of the DNO (POCO) to maintain an effective earth. They?re famous for trying to avoiding their duty to maintain an effective earth.
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But it doesn't necessarily to be ground rods correct? As long as Ze of the DNO neutral or PE is a stable 0.5 ohms a simple wire back to the star point is sufficient?
 
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