Chain link fencing bonding

[Dumbo2929]

Can anyone tell me if there is a requirement in the 2008 NEC (because I can't find one) that requires a metal chain link fence to be grounded with an intentional ground rod, etc. under the following situation. There is an existing million+ gallon municipal water storage tank on a site. There are a few upgrades going on, including a new electrical service for security lighting and to replace some worn out components in the pump vault (in the ground near the tank). The project along includes a new chain link fence around the site to keep vandals out. The inspector says the fence needs to be bonded to the water tank. I cannot find the requirement. Anyone have any thoughts

 

[rcw retired EE]

No NEC requirement. But the inspector is the AHJ (Authority Having Jurisdiction), what he wants he gets.

Bonding the fence won't hurt anything except your costs, but probably won't help safety much either.

 

[dpc]

What is the closest distance between the fence and the tank?



"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[Dumbo2929]

The closest point to from the water tank to the fence is 11 feet.

 

[dpc]

That would be a big wingspan. I could see some reason to do it if someone could touch both at the same time.

Not aware of an NEC requirement. It's required in substations.

But it might be less expensive to just do it rather than argue with the inspector. You may need a little good will for other arguments to come.

 

[busbar]

OT a little, but I found this {apparently new work} in an old 69:12kV station. Any suppositions for its application?

It's a bit hard to see in the shadow, but the center post jist clears the base rock.

 

[Kiribanda]

busbar,

Very useful picture.Is it from a SVC installation,where the fence has to be broken at several places to mitigate circulating ground currets generated by the magnetic reactors?

Dumbo2929,
I donot think you need to bond the fence to the tank due to,
1)The fence is 11 ft(3m away)from the tank. If there is a ground fault in the tank structure, then the most of the voltage drop through the soil is only effective within the first 2m span maximum.

 

[rcw retired EE]

Thsi looks like an isolating section intended to split the fence electrically. If there is a long fence but only a portion of it is near or on the ground grid, isolating sections can prevent the transferred potentials during a fault.

I have my doubts that this style of isolation actually works. The two posts on either end are essentially connected together through the earth.

We use a 2.5 meter section of wood or plastic fence as an isolation. The length is selected to prevent someone from touching both grounded parts of the fence at the same time. Fence on either side of the isolation are connected/bonded to local ground grids or rods.

 

[busbar]

 
Kiribanda—

The station is fairly small [probably <7.5MVA...serving a ~60-year-old low-head hydro machine] and peering though the fence slats, doesn't look like it has any reactors or even capacitors.

 

[rockman7892]

I dont think installing an isolated ground rod for the fence will do anything in regard to clearing faults, or reducing touch potential either. I would not see a reason for installing a seperate ground rod.

Someone please correct me if I am wrong.