Solidly grounding

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cppoly

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Trying to understand this statement from an article I'm reading, "Solid grounding facilitates the automatic clearing of ground faults by circuit protective equipment (fuses and circuit breakers) because solid grounding results in the highest magnitude of ground fault current".

I thought solidly grounding refers to connecting the neutral of a system directly to ground without any resistance in between this connection. How does this assist in clearing faults quickly??? I thought bonding does that.
 
cppoly said:
Trying to understand this statement from an article I'm reading, "Solid grounding facilitates the automatic clearing of ground faults by circuit protective equipment (fuses and circuit breakers) because solid grounding results in the highest magnitude of ground fault current".

I thought solidly grounding refers to connecting the neutral of a system directly to ground without any resistance in between this connection. How does this assist in clearing faults quickly??? I thought bonding does that.
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It is both together that do that. Bonding makes all conductive materials that do not intentionally carry current, electrically continuous. Solid grounding establishes that the neutral conductor is electrically continuous at exclusively one point, with the non-current-carrying conductive materials (EGC system). Such that if an ungrounded live wire faults to any piece of metal in the EGC system, it short circuits through the EGC system and exceeds the trip rating of its OCPD.

Had there been no current-carrying conductors connected to ground anywhere, just one instance of a current-carrying-conductor faulting to ground will go undetected. The remaining conductors will float in voltage relative to the now solidly grounded conductor (that was never intentionally connected to ground).
 
cppoly said:
I thought solidly grounding refers to connecting the neutral of a system directly to ground without any resistance in between this connection. How does this assist in clearing faults quickly??? I thought bonding does that.
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You have it right. All of the bonding comes back to one point, the Main Bonding Jumper, at the service creating what we call a solidly grounded system. This is different than someone trying to use a distant ground rod to carry fault current.
 
You are correct in your understanding of the physics. It is the solid bonding of conductors that aren't supposed to be current carrying, and the solid bonding of one of the transformer terminals to these conductors that provides for high fault current and rapid operation of protective equipment.

My understanding is that the term 'solid grounding' refers to the connection between the transformer and the bonded non-current carrying metal.

Since all of the bonded non-current carrying metal is supposed to also be connected to earth, it is not unreasonable to call the non-current carrying metal 'grounded', to call this bonding process 'grounding', and to call the circuit conductors connected to the bonded terminal 'grounded conductors', but I agree: the connection to soil is not what assists in clearing faults quickly.

-Jon
 
While we just say "grounded system" in most everyday usage, most grounded electrical systems are in fact more technically "solidly" grounded systems. This is important as the NEC recognizes both solidly grounded systems and resistance grounded systems.
 
texie said:
While we just say "grounded system" in most everyday usage, most grounded electrical systems are in fact more technically "solidly" grounded systems. This is important as the NEC recognizes both solidly grounded systems and resistance grounded systems.
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And more recently, it recognizes functionally grounded systems, where the current carrying conductor at ground voltage is connected to ground through a ground fault OCPD.
 
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