solidly grounded

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petersonra

petersonra

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Semi-retired engineer
I have been going thru a spec the last few days.

It refers to the power as being 480V, 3 wire, solidly grounded. I am thinking corner grounded delta.

However, later in the same spec it refers to the power as being 480V, 4 wire, solidly grounded. I am thinking 480/277V wye.

As a practical matter it does not change anything for us other than some minor details.

How many of you would interpret the phrase "solidly grounded" the way I did, given the context? Just curious.

Does solidly grounded actually mean anything specific? i can't say I have seen the phrase before.
 
petersonra said:
I have been going thru a spec the last few days.

It refers to the power as being 480V, 3 wire, solidly grounded. I am thinking corner grounded delta.

However, later in the same spec it refers to the power as being 480V, 4 wire, solidly grounded. I am thinking 480/277V wye.

As a practical matter it does not change anything for us other than some minor details.

How many of you would interpret the phrase "solidly grounded" the way I did, given the context? Just curious.

Does solidly grounded actually mean anything specific? i can't say I have seen the phrase before.
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NEC defines solidly grounded as ...Grounded, Solidly. Connected to ground without inserting any resistor or impedance device.

To What point of the source (corner tap, midpoint wye) ground is solidly connected to is up to more information in defining the source connection.

I'm with you, sounds like a conflict.
 
markstg said:
NEC defines solidly grounded as ...Grounded, Solidly. Connected to ground without inserting any resistor or impedance device.

To What point of the source (corner tap, midpoint wye) ground is solidly connected to is up to more information in defining the source connection.

I'm with you, sounds like a conflict.
Click to expand...

I never thought to look it up in the code. The phrase makes sense to be as defined in the code. Just never saw it before.

I can't think of any way to have 3 wire 480 that is solidly grounded other than corner grounding though.

I have never actually run across a 480V corner grounded system before. Maybe a new first for me.:)
 
I would read the 480 volt, 3 wire, solidly grounded as a wye system that does not feed any line to neutral loads and does not have a neutral run out of the transformer. I would read the 480 volt, 4 wire, solidly grounded as a wye system with a neutral extended to the loads.
 
don_resqcapt19 said:
I would read the 480 volt, 3 wire, solidly grounded as a wye system that does not feed any line to neutral loads and does not have a neutral run out of the transformer.
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If the neutral is bonded to an electrode or MGN at the transformer but not fed to the building, would this not set up potential through earth with the grounding at the building? never ever heard of doing this.:confused:
 
hurk27 said:
If the neutral is bonded to an electrode or MGN at the transformer but not fed to the building, would this not set up potential through earth with the grounding at the building? never ever heard of doing this.:confused:
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An EGC is run to the building. This is a common industrial distribution installation. You can't use this method for a service because the code requires the grounded conductor to be run to the service disconnect, but you can use it for SDS installations.
 
Unless it is ungrounded or impedance ground system it is solidly grounded no matter what the voltage is or number of phases.

In a solidly grounded system if an ungrounded conductor contacts a grounded/grounding conductor or other well grounded object there is high level of current in the fault.

In other than solidly grounded system if an ungrounded conductor contacts a grounded object there is no hazardous level of current - but there should be a detection system to indicate there is a ground fault so the equipment can be shut down in a timely manner to repair the fault.
 
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