Replacing ABB commercial inverters

Ok so what are the implications of this bastard grounded system? To review, say we have the wye point earthed several hundred feet from the building, with no bonding/grounded conductor run to the building. The building has all metal bonded and earthed to a GES.
They treat it as an ungrounded system. What are the implications of the utility having made a ground connection? It actually seems like it might be taking some of the best of both worlds.
 
Seems basically like it would essentially be an impedance grounded system no? The big risk I see is first fault current taking paths of other than just the dirt, such as communication cable Shields and what not, could do lots of damage during a fault. If this was an MGN distribution system, then you open the door for many more potential parallel paths such as water lines.
 
electrofelon said:
Seems basically like it would essentially be an impedance grounded system no? The big risk I see is first fault current taking paths of other than just the dirt, such as communication cable Shields and what not, could do lots of damage during a fault. If this was an MGN distribution system, then you open the door for many more potential parallel paths such as water lines.
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Just for clarification, in the system I was describing although there was no neutral run to the buildings there was an EGC back to the service.
 
ggunn said:
Just for clarification, in the system I was describing although there was no neutral run to the buildings there was an EGC back to the service.
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Ok so then it is like I described in post #36. It's just a regular grounded service although the only difference is they / you are calling the grounded conductor an EGC. Is there a grounding electrode system at the building or is the only Earth connection at the transformer? Regardless of the system grounding topology there should be a grounding electrode system at the building.
 
electrofelon said:
Ok so then it is like I described in post #36. It's just a regular grounded service although the only difference is they / you are calling the grounded conductor an EGC. Is there a grounding electrode system at the building or is the only Earth connection at the transformer? Regardless of the system grounding topology there should be a grounding electrode system at the building.
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Yes. There was a junction box on the wall at the building on the other end of the feeder that fed three or four 3P3W disconnects. There was a ground bar in the box that had EGCs to the discos and into the conduit from the service, and it also had a bare copper conductor going into the dirt below it. I don't remember if there was a visible ground rod there or not.
 
jaggedben said:
Where was the service point?
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The transformer and utility meter were 200-300 feet away. A correction that I do not know if makes a difference is that I have possibly been incorrectly referring to this as a service configuration. There was switchgear near the transformer and what I was dealing with was a feeder from the switchgear; there was a breaker in the switchgear that powered the feeder. Upon reflection (it was five years ago and all this is all from memory) I don't know if there was a neutral run to the switchgear or not, only that there was no neutral in the feeder. I am also remembering that someone at the site told me that there had been a fire in the original transformer some years before and it had been replaced.
 
ggunn said:
There was switchgear near the transformer and what I was dealing with was a feeder from the switchgear; there was a breaker in the switchgear that powered the feeder.
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Everything you described is normal and required for a 3P3W feeder to a separate building. Namely EGC in the feeder, and a GES at the building, connected to the EGC.

ggunn said:
Upon reflection (it was five years ago and all this is all from memory) I don't know if there was a neutral run to the switchgear or not
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If the switchgear was the service disconnect, as it sounds like, then there was if the install was NEC compliant. The switchgear should contain the MBJ, which connects the EGC to the grounded service conductor; as none of the loads on the feeder required a neutral, no neutral was required for the feeder.

Cheers, Wayne
 
Just a comment relating to this: I have wondered why the NEC requires the grounded conductor always be run to the service disconnect even if not used. Yes there needs to be a bonding/fault clearing conductor, but why can't we run a SSBJ like we can for an SDS?
 
electrofelon said:
Just a comment relating to this: I have wondered why the NEC requires the grounded conductor always be run to the service disconnect even if not used. Yes there needs to be a bonding/fault clearing conductor, but why can't we run a SSBJ like we can for an SDS?
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When the service point supplies only one service disconnect, the only difference is terminological; electrically it's the same.

When the service point supplies multiple service disconnects, I do think it would be a useful option to install a single MBJ in a common location on the utility side of more than one service disconnect.

Cheers, Wayne
 
electrofelon said:
Just a comment relating to this: I have wondered why the NEC requires the grounded conductor always be run to the service disconnect even if not used. Yes there needs to be a bonding/fault clearing conductor, but why can't we run a SSBJ like we can for an SDS?
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It's just the naming convention. If it's on the line side of a service disconnect it's called a grounded conductor. It's minimum sized to 250.102 regardless.
 
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