Definition Of Conductors

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tnt8197

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Good Afternoon Everyone,

I am having a friendly debate with an electrical counterpart regarding what the conductors on the attached are defined as. What we have is a 1/4" x 4" continuous copper bar around the perimeter of the substation room and from that copper bar we have 4/0 conductors to the associated substations. I am trying to keep my question as vague as I can, so as not to influence anyone's answer.

Your assistance is appreciated.

Thank you.
 

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tnt8197 said:
Good Afternoon Everyone,

I am having a friendly debate with an electrical counterpart regarding what the conductors on the attached are defined as. What we have is a 1/4" x 4" continuous copper bar around the perimeter of the substation room and from that copper bar we have 4/0 conductors to the associated substations. I am trying to keep my question as vague as I can, so as not to influence anyone's answer.

Your assistance is appreciated.

Thank you.
Click to expand...

I don't understand the question. Is this a feeder vs. branch circuit thing question?
 
My apologies, the copper bar around the substation room is a ground bar and this is the main point the system. Hope this clarifies.

Thank you
 
Here is the full drawing of the area. I was trying not to show this so as not to influence anyone's answers.

Thank you again.
 

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tnt8197 said:
Good Afternoon Everyone,

I am having a friendly debate with an electrical counterpart regarding what the conductors on the attached are defined as. What we have is a 1/4" x 4" continuous copper bar around the perimeter of the substation room and from that copper bar we have 4/0 conductors to the associated substations. I am trying to keep my question as vague as I can, so as not to influence anyone's answer.

Your assistance is appreciated.

Thank you.
Click to expand...

I'm not sure what the official term would be if there is one, but I consider it a supplemental EGC. (off subject a bit, I've been on this rant for awhile) The gas and oil industry seems to like supplemental grounding, including ground rings in the earth, connected to every metallic object in a plant including a metallic MCC/PDC building. I understand the importance of grounding and bonding, but in a building with switch-gear, etc. already grounded per NEC, this supplemental grounding system adds a parallel path for fault currents which doesn't follow the supply conductors, which seems to me to be a negative. The NEC has been altered over the years for instance to make sure this doesn't happen on SDSs, etc. Thoughts? If this should be a new thread, I understand.
 
Jim1959 said:
I'm not sure what the official term would be if there is one, but I consider it a supplemental EGC. (off subject a bit, I've been on this rant for awhile) The gas and oil industry seems to like supplemental grounding, including ground rings in the earth, connected to every metallic object in a plant including a metallic MCC/PDC building. I understand the importance of grounding and bonding, but in a building with switch-gear, etc. already grounded per NEC, this supplemental grounding system adds a parallel path for fault currents which doesn't follow the supply conductors, which seems to me to be a negative. The NEC has been altered over the years for instance to make sure this doesn't happen on SDSs, etc. Thoughts? If this should be a new thread, I understand.
Click to expand...

I've done a lot of work on cell sites and they have a similar earthing scheme, along with everything, and I mean every single cotton picking thing, metal having a copper bonding jumper above and beyond the normal EGC back to a big copper buss. I don't see any problem with it.
 
iwire said:
.........
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Why would you consider this a bonding jumper in lieu of a grounding conductor? The conductors are going from the main grounding bus bar to the downstream portion of the unit substations? Wouldn't that be the main grounding conductor for the separately derived system?
 
iwire said:
Bonding Conductor or Jumper. A reliable conductor toensure the required electrical conductivity between metal
parts required to be electrically connected.
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Click to expand...

tnt8197 said:
Why would you consider this a bonding jumper in lieu of a grounding conductor? The conductors are going from the main grounding bus bar to the downstream portion of the unit substations? Wouldn't that be the main grounding conductor for the separately derived system?
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How are we supposed to know what the units are? 'Substation' is not a descript NEC term. Now if you say the units are SDS's, then we have the possibility of one being a GEC, another being an BC/BJ (likely an EBJ), while another being an SSBJ or an EGC. Note that an SSBJ or EGC will only be run with circuit conductors.

Under the NEC
  • an EGC is required to be run with the primary conductors
  • an SSBJ is required to be run with the secondary conductors
  • a GEC is required for grounding the secondary if it is a grounded system, and it must be run to the same enclosure where the SBJ is located
  • an EBJ could be required but in most cases it is a superfluous and not required in most industrial scenarios
 
Smart $ said:
... 'Substation' is not a descript NEC term....
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For what it's worth...

Article 100, Part II...
Substation. An enclosed assemblage of equipment
(e.g., switches, interrupting devices, circuit breakers,
buses, and transformers) through which electric energy
is passed for the purpose of distribution, switching, or
modifying its characteristics.
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It was new in the 2014 NEC.

And also see 250.191 and 250.194
The term 'bonding jumper' is used.

I'm inclined to agree with iwire.
 
jaggedben said:
For what it's worth...



It was new in the 2014 NEC.

And also see 250.191 and 250.194
The term 'bonding jumper' is used.

I'm inclined to agree with iwire.
Click to expand...
Well, I'll be... :ashamed1:

Thanks for pointing that out.




The answer to the query as posed is IMO as iwire responded: bonding conductor or jumper. As details are revealed, such as being an SDS, more specific acronyms will apply. :happyyes:
 
My concern is that in the event of a fault, current will flow on all parallel paths. Not only will it not all flow with the energized conductor path as it should, but current will flow through the supplemental bonding (or whatever you desire to call them) conductors. This can cause extreme heating as well as the potential to shock a person who might be in contact with the supplemental grounding system, thereby creating an additional path for current flow. With properly engineered over-current/fault current protection, the time frame in which this could happen is minimal, but the NEC has minimized this potential over the years from my understanding. Thoughts?
 
Jim1959 said:
My concern is that in the event of a fault, current will flow on all parallel paths. Not only will it not all flow with the energized conductor path as it should, but current will flow through the supplemental bonding (or whatever you desire to call them) conductors. This can cause extreme heating as well as the potential to shock a person who might be in contact with the supplemental grounding system, thereby creating an additional path for current flow. With properly engineered over-current/fault current protection, the time frame in which this could happen is minimal, but the NEC has minimized this potential over the years from my understanding. Thoughts?
Click to expand...
Despite my gripes about the NEC it is still a good safety standard. I don't need a silver plated Cadillac to get me to work everyday, my old Honda is perfectly safe.

As far as over doing it with the earthing scheme, it doesn't really matter how much you connect to the earth you are not really going to send that much more current into it during a fault.

Check out this old thread, http://forums.mikeholt.com/showthread.php?t=116358
 
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