Fence Grounding

nhee2

Senior Member
Location
NH
Beyond substations with exposed/energized equipment/busses, (and maybe swimming pools) is there any other condition where the NEC requires fencing to be grounded? Just reviewed a plan for perimeter fencing around a large gas facility, which specs grounding of fence posts. I'm not sure of the basis or technical justification for this.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Beyond substations with exposed/energized equipment/busses, (and maybe swimming pools) is there any other condition where the NEC requires fencing to be grounded? Just reviewed a plan for perimeter fencing around a large gas facility, which specs grounding of fence posts. I'm not sure of the basis or technical justification for this.
Often, the basis and justification for doing something is that "we have always done it that way".

AFAIAC, you can't get much better grounded that a metal pole stuck in some concrete in the ground.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Beyond substations with exposed/energized equipment/busses, (and maybe swimming pools) is there any other condition where the NEC requires fencing to be grounded? Just reviewed a plan for perimeter fencing around a large gas facility, which specs grounding of fence posts. I'm not sure of the basis or technical justification for this.
To limit sparking as an ignition source would be a SEWAG.
 

nhee2

Senior Member
Location
NH
To limit sparking as an ignition source would be a SEWAG.
I don't know what would be the initiator of the spark, if there are no electrical sources in the vicinity. and if they are just grounding every few posts (not every post) then it seems to not provide any value.
 
Often, the basis and justification for doing something is that "we have always done it that way".

AFAIAC, you can't get much better grounded that a metal pole stuck in some concrete in the ground.
Did a 2 MW solar farm two years ago. Had whatever it was - almost a mile perimeter of fencing. Metal posts in concrete. We had to drive a ground rod every 200 feet to "ground" the fence :slaphead:
 

paulengr

Senior Member
This is usually IEEE driven. In a substation environment IEEE 80 states that fencing should be bonded and grounded and makes a big deal about the fence. There are also vague questions about how far the equipment should be from a fence. And the whole ground grid thing is crazy once you get away from overhead tubular construction. Might be due to induced voltages. In testing around 230 kV subs once in a while and by this I mean 2-3% of the time I will find maybe one rod that has a high resistance and they’re all bonded together but this is rare.

So might want to start with that standard. IEEE standards are a little annoying because often they are more of a cookbook with little or no guidance and it’s up to the end user to find the right recipe. There were even 2 partial sentences in the IEEE arc flash standard (1584-2002) where a couple things were mentioned more or less in passing like the 2 second rule. They became almost enshrined as requirements.


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nhee2

Senior Member
Location
NH
This is usually IEEE driven. In a substation environment IEEE 80 states that fencing should be bonded and grounded and makes a big deal about the fence. There are also vague questions about how far the equipment should be from a fence. And the whole ground grid thing is crazy once you get away from overhead tubular construction. Might be due to induced voltages. In testing around 230 kV subs once in a while and by this I mean 2-3% of the time I will find maybe one rod that has a high resistance and they’re all bonded together but this is rare.

So might want to start with that standard. IEEE standards are a little annoying because often they are more of a cookbook with little or no guidance and it’s up to the end user to find the right recipe. There were even 2 partial sentences in the IEEE arc flash standard (1584-2002) where a couple things were mentioned more or less in passing like the 2 second rule. They became almost enshrined as requirements.
Thanks for the response. I agree IEEE 80 would provide guidance for substations and grounding of fence in a substation. I am guessing the details shown in the drawings I reviewed are a cut-and-paste from a substation job. in this case I don't think IEEE 80 applies. They'll be installing 5000 ft of 4/0 copper, a bunch of rods, clamps, cad-welds, etc. with (in my opinion) very little if any benefit. There's some MV distribution on site that comes in below-grade to a switchgear lineup, but no overhead distribution or other installation that could be considered substation.
 
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