3 phase transformer grounding

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All right, I cant' restrain myself any further, I tried, but why shouldn't this so significantly important grounded conductor connection be hard-wired?

I mean really, if this thing means so much, why is this somewhat hoky fuse holder connection accepted as a satisfactory means of a permanent grounded conductor connection to a grounding system?

Maybe it's just me.
 
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physis said:
All right, I cant' restrain myself any further, I tried,
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I think you can hire people to help with that. :wink:

I mean really, if this thing means so much, why is this somewhat hoky fuse holder connection accepted as a satisfactory means of a permanent grounded conductor connection to a grounding system?
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My guess is a long history of no problems.

I have never run into one of these dummy fuses, all most all the 3 phase I work with is supplied from Wye systems.
 
physis said:
. . . why shouldn't this so significantly important grounded conductor connection be hard-wired? . .
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When you use this configuration, it is normal to switch the neutral; therefore, you install a dummy fuse (slug) in the grounded conductor position.

If you wanted, you could have used two pole equipment and taken the grounded conductor to the neutral bar. It is fairly common to take a 240 volt corner grounded delta service to a two pole circuit breaker panelboard for a service to a three phase lift station from an open delta bank. The electrician would use two pole fully rated circuit breakers to run two phases and a grounded conductor to the three phase equipment. Everything looked like single phase except it was all full voltage rated and was three phase. :smile:
 
physis said:
All right, I cant' restrain myself any further, I tried, but why shouldn't this so significantly important grounded conductor connection be hard-wired?

I mean really, if this thing means so much, why is this somewhat hoky fuse holder connection accepted as a satisfactory means of a permanent grounded conductor connection to a grounding system?

Maybe it's just me.
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It's you.

J/K.

It's no hokier than any other switch, fuse, etc., in the system.

It's not 'life-critical' to maintain the connection, but think what would happen if a main grounded-conductor fuse opened: the entire what-should-be-grounded-conductor system would become energized.

A corner-grounded Delta's grounded conductor is really no different from any other grounded-conductor system. The typical 120/240v neutral is not 'safer' or 'less mysterious' than the grounded corner.

Think about it: the line-to-ground voltage of a 480Y/277v is higher than that of a corner-grounded 240v Delta system, and nobody seems to be so scared of it. It's just a grounded conductor, like any other.
 
LarryFine said:
It's you.

J/K.

It's no hokier than any other switch, fuse, etc., in the system.

It's not 'life-critical' to maintain the connection, but think what would happen if a main grounded-conductor fuse opened: the entire what-should-be-grounded-conductor system would become energized.

A corner-grounded Delta's grounded conductor is really no different from any other grounded-conductor system. The typical 120/240v neutral is not 'safer' or 'less mysterious' than the grounded corner.

Think about it: the line-to-ground voltage of a 480Y/277v is higher than that of a corner-grounded 240v Delta system, and nobody seems to be so scared of it. It's just a grounded conductor, like any other.
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I understand everything you've said Larry, that's why I ask how this slug is such a good idea. I guess what Bob says about minimal failures makes "some" sense.
 
I just worked on a residensial service sub panel that lost a leg due to corrosion. Isn't this a concern?
 
LarryFine said:
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A corner-grounded Delta's grounded conductor is really no different from any other grounded-conductor system. The typical 120/240v neutral is not 'safer' or 'less mysterious' than the grounded corner.
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Actually I think that the grounded conductor of a corner grounded system is much more like a ungrounded conductor of a more conventional system. (at least the portion of the grounded conductor that is on the load side of the main bonding jumper). It is a phase conductor and the problems caused by a failure of this conductor are the same as the failure of any phase conductor.
 
don_resqcapt19 said:
Actually I think that the grounded conductor of a corner grounded system is much more like a ungrounded conductor of a more conventional system. (at least the portion of the grounded conductor that is on the load side of the main bonding jumper). It is a phase conductor and the problems caused by a failure of this conductor are the same as the failure of any phase conductor.
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But Don, how do you ignore the grounding issue?
 
physis said:
All right, I cant' restrain myself any further, I tried, but why shouldn't this so significantly important grounded conductor connection be hard-wired?

I mean really, if this thing means so much, why is this somewhat hoky fuse holder connection accepted as a satisfactory means of a permanent grounded conductor connection to a grounding system?

Maybe it's just me.
Click to expand...

Maintained isolation against backfeed?
 
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