continuous grounding conductor

[Ed MacLaren]

Re: continuous grounding conductor

My definition of single point ground is single point ground (as in earth) not as in buss bars.

The term "single point grounding" does not mean that the Grounding Electrode Conductor (GEC) is connected to the earth at one point only.
In order to accomplish this, metal enclosures, conduits, and cable sheaths would have to be isolated from the earth, and everything in contact with the earth. That is clearly impractical.

As long as there is a "single connection" at one point in the GEC there can't be objectionable current flow.

It is much more practical to make the "single connection" at one point on the grounded (neutral) conductor, and isolate the neutral from ground thereafter.

The term "single point grounding" means that the GEC/GECs is/are connected to the grounded (neutral) conductor at one point within each facility.

The grounding electrode "system" can be comprised of any number of individual grounding electrodes, the more the better, as long as they are interconnected with the correct size wire.

Ed

[ April 14, 2003, 09:28 AM: Message edited by: Ed MacLaren ]

 

[dereckbc]

Re: continuous grounding conductor

Ed, I partially agree with your definition of SPG. I believe it should be broken down into two definitions, one for power supplies and one for load equipment. SPG for power supplies is practical in any application, it is the load that is not practical in most applications.

SPG (for Power Supplies)
When one current-carrying member of a separately derived power source is connected to a ground reference at only one point, it is single-point grounded. (In contrast to this, grounded conductors having more than one connection to a ground reference along their length are classified as multi-grounded systems) Currents from lightning, external faults, and external load currents cannot flow on single-point grounded current-carrying members.

Examples of SPG power supplies.
? The entrance ac power to a building by a single connection from its neutral to the main grounding electrode system.
? Transformers to a building by a single connection from its neutral to the main grounding electrode system.
? Generators to a building by a single connection from its neutral to the main grounding electrode system.
? Battery plants to a building by a single connection from its neutral to the main grounding electrode system.
? Solar photovoltaic system to a building by a single connection from its neutral to the main grounding electrode system.

SPG (for load equipment)
A method used to ground an individual equipment load or a set of equipment loads that can have only one grounding connection from the given load to a planned ground reference. Because the load equipment does not have multi-connections (either planned or incidental) to other ground references, it is classified as an isolated ground plane.

 

[lwciak]

Re: continuous grounding conductor

Separately Derived System. A premises wiring system whose power is derived from a battery, from a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.

There are other references in the 2002 NEC that make mention and help define a SDS including a switched neutral.

I interpet this to mean as long as there is no common bonding or grounding it is a SDS.

 

[don_resqcapt19]

Re: continuous grounding conductor

Iwciak,

I interpet this to mean as long as there is no common bonding or grounding it is a SDS.

This is a problem with the wording of the code. A grounding conductor is not a "circuit conductor" and the fact that there is common grounding between systems does not prevent one of them from being SDS.
Don