Grounding Wire Requirements 1

[MIMAN]

What is the code requirement when running grounding wire from industrial equipment that is located outside. Does the ground wire need to be ran through PVC conduit or can it be ran as an exposed wire?

 

[squeeky]

In South Africa you can run a bare copper conductor. If your soil has stray currents in it or acidic, you may wish run a PVC insulated conductor. Failing this, you may wish to bury some sacrificial anodes in the ground.

 

[waross]

Beware if this is a petrochemical installation designed under the American Petroleum Institute code. API grounding is much more demanding than North American basic wiring codes.
One of many instances is the grounding of cable trays. The trays are mounted on and connected to grounded steel structures and would be considered adequately grounded under the CEC. API requires a ground conductor to be run in a single tray and in one of multiple tray runs. The multiple trays must be grounded by jumpers to the running ground cable at regular intervals.
First determine what codes apply to your installation.
The only bare copper that I see is ground grids. Above ground ground cables are insulated to avoid galvanic corrosion from contact with steel and aluminum.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

The following may not be a factor in your area; nevertheless...

Aside from code requirements, you may wish to consider running all copper grounding conductors in thick steel conduit as a means of deterring theft; our utility has an ongoing problem with grounding conductor being stolen.

Despite laser-etching of the grounding conductor itself, use of concealed cameras and proximity detectors and numerous other approaches, loss of grounding conductor continues to be 'issuematic' [a word I coined - grin], and considerable labour cost is being incurred to have it all replaced, along with having to take equipment outages, etc., etc.

CR

 

[waross]

Running grounding conductors in steel conduit is bad practice. The steel encirclement adds considerable inductance and impedance to the ground path. You are putting a very effective choke in series with your circuit. Long ago I read some test results that showed that a 1/2" conduit would choke off the current through a single conductor to 100 or 200 amps. Not a good thing in a ground circuit.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Hi Bill,

I take your point; and I didn't mean to suggest that this be done without applying the necessary corrections to compensate for any electrical effects that encasing in steel conduit might have.

Still: the problem of copper theft remains...so the question becomes whether 'tis better to have to address the altered performance of the ground conductor encased in steel versus that nasty difference of potential that arises between a piece of equipment and earth if a fault occurs when there is no grounding present at all, without even getting too far into the effect this has on the operation of protective schemes...

And not all of the ground conductor needs to be encased, only that part that runs from the point of attachment to a foot [30 cm] or so below grade, since thieves tend to be lazy and won't generally excavate just for copper; they also tend to hate getting caught, and having to do spadework increases their loiter time significantly.

CR

 

[7anoter4]

First of all I think waross is right: run a grounding cable in a steel conduit it is a bad idea. But if this cable run in the same conduit with the all other live conductors of the service feeder is better. But, any way, I would connect this cable to the steel conduit at both ends and care about electric continuity of the steel conduit.
However, the code [NEC] recommends to run the grounding cable close to the service feeder live conductors [that means in the same conduit or raceway, I think]

 

[waross]

Rigid PVC and rigid aluminum conduits are acceptable alternatives to steel. We do a lot of structure grounding in petro-chemical plants with rigid PVC conduit used for mechanical protection.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

Oops...

The OP mentioned grounding industrial equipment out of doors; I related our utility's experience with the grounding of medium- and high-voltage electrical equipment in switchyards, which may not have been apropos.

Mmmm, mighty tasty crow...

CR

 

[racookpe1978]

More than electrogalvanic corrosion, I see a LOT of wear and tear damage (stepping, rubbing, bending, fatigue, etc) on exposed copper. When run inside PVC, that daily damage is prevented. And, true, out-of-sight can reduce the off-of-site theft problems.

 

[squeeky]

PVC is better than the conduit as there is no electromagnetic problems. Aluminum conduit could have problems in soils with high ph as it will corode. This is relevant in agricultural installalations. Aluminium conductors are not permitted due to above reasons. IEC Sstandards do list stainless steel as an alternative.

Conductor theft is a problem here too. They tie the conductor to the junkie (utility vehicle) and drive in the direction that the conductor comes from. When they have run out of time, they cut it off with bolt cutters and continue to drive to a quite location where it is rolled up for disposal. Now some people throw concrete into the trench before they cover up.

 

[dpc]

For a feeder circuit, the ground wire needs to be run in the same conduit as the phase conductors to be truly useful. If run outside the main conduit, the inductance increases drastically. Running the ground wire inside a separate steel conduit would be much worse.

I highly recommend the GE paper linked below written by R.H. Kaufmann. Nothing has changed in the last 50 years.

http://www.powercet.com/uploads/files/GE-More_Specific_Eqpt_Gnd.pdf