question about grounding cable size from high mast/lighting pole to grounding rod

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mustafa said:
Please help about method to determine grounding cable size from high mast and or lighting pole to the grounding rod?
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the nec does not require a grounding rod or other grounding electrode for a pole mounted light.

if the spec requires a ground rod, one would think the spec would tell you what size wire to connect to it. best bet is to ask whomever is making you do this unnecessary work.
 
On our high mast luminaires we run a 2/0 to the ground ring from the pole and thre ring is also a 2/0

This is just to "eliminate static charges and dissipate the energy from a lightning event":thumbsup:
 
Since there is no NEC requirement for a ground rod at a lighting pole, its considered an auxiliary electrode and thus the rules for a GEC don't apply.
However for lighting protection, due to is high frequency, there is little difference in the impedance between 6 AWG and 4/0. I have a slide chart from Polyphaser that calculates the impedance. Impedance is drastically lowered by using a flat copper conductor, say 4" wide.
Since you want just a simple and quick answer, I would go with a 2 AWG BCS, its large enough to give you some protection against damage. Cell towers typically use a 2/0 BSC, and both would be cad welded.
 
mustafa said:
This article didnot show grounding cable size
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Sure it does.

(5) Metal raceways or other equipment grounding conductors
shall be bonded to the metal pole with an equipment grounding conductor recognized by 250.118 and sized in
accordance with 250.122.

Is the NEC the appropriate set of standards for Saudi Arabia?
 
410.30B is for equipment bonding (grounding), and does not apply to your question, other than a EGC is required with the circuit supplying the pole . What you are asking about is in 250.64

250.54 Auxiliary Grounding Electrodes. One or more
grounding electrodes shall be permitted to be connected to
the equipment grounding conductors specified in 250.118
and shall not be required to comply with the electrode
bonding requirements of 250.50 or 250.53(C) or the resistance
requirements of 250.53(A)(2) Exception, but the
earth shall not be used as an effective ground-fault current
path as specified in 250.4(A)(5) and 250.4(B)(4).

Since what you are asking about is not required, its up to you to determine how to do it. 2/0 BSC cadwelded would be suitable.
(Although its likely the concrete pole base is a far better ground than your ground rod) One other recommendation is to bond the rebar in the foundation to the pole base bolts
 
410.30(B) is the requirement. 250.54 is optional. I would agree with Tom but would also point out that since 250.66(A) will not require a GEC connected to a rod to be larger than #6 why would a 3/0 be considered for a supplemental earth reference?
 
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I think we should refer to NFPA 780 about this regard as long the cable will be used to discharge the electrical strike,bonding the bolt to pole steel foundation could lead to galvanic corrosion, i am still searching for the article about that .
 
mustafa said:
I think we should refer to NFPA 780 about this regard as long the cable will be used to discharge the electrical strike,bonding the bolt to pole steel foundation could lead to galvanic corrosion, i am still searching for the article about that .
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I am sorry but it is not required by 780 either unless you want to shoehorn it to fit here:

5.2 Masts,Spires,Flagpoles.
5.2.1 These slender structures shall require one strike termination device, down conductor, and grounding electrode.
5.2.2 Electrically continuous metal structures shall require
only bonding to grounding electrode(s).

The answer will be the same. If you must do it I would use the same size as your EGC appropriately sized up with the circuit conductors for voltage drop or no larger than a #6.

Read Me.
a little dated but still relevant.
 
BTW, the bonding conductor size for Class 1 structures (75' or less) is 26,240 cir. mils or a #6 awg so if 780 does fit you are still OK with #6 awg

Capture.jpg
 
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mustafa said:
What about the high mast 30meter long and fitted by air terminal at the top to protect the lighting fixtures
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Well if you put an air terminal up there it will need a full size down lead conductor at min 115,000 cir. mils but frankly it will not protect the light from damage in a strike rather may provide limited protection to surrounding structures. But once again this is optional IMO.

5.2.2 Electrically continuous metal structures shall require
only bonding to grounding electrode(s).
 
luckylerado said:
Well if you put an air terminal up there it will need a full size down lead conductor at min 115,000 cir. mils but frankly it will not protect the light from damage in a strike rather may provide limited protection to surrounding structures. But once again this is optional IMO.

5.2.2 Electrically continuous metal structures shall require
only bonding to grounding electrode(s).
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High masts shall be equipped with an air terminal of the correct height to provide the required zone of protection for the mast head frame and fixtures . The air terminal shall be bonded to the mast to ensure the discharge is dissipated via the earth connection and system without damage to the steel winch ropes or the electrical cables. but i am still asking about the two issues

Can i use mast steel body as down conductor if continuity is ensured, if the answer is no what is the down conductor size is required by the code
if the answer is yes what is the grounding cable size from mast stud to rod?:happyno:
 
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