Grounding SCADA Antenna

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walton

Member
Location
Sacramento, CA
I have a project where we are upgrading 11 Water Agency SCADA sites. The sites are pumping stations for well water and have utility supplied electrical services with MCCs. The design calls for 20' of #4 cu wire and a ground rod to be installed in the concrete pole base and attached to the grounding post in the antenna pole handhole. I asked the question to the PE as to whether the grounding electrode of the new antennas should be attached to the grounding electrode system of the existing on site electrical service per 810.21. The answer was no "because there is no building (structure) on site there is no need to connect the grounding systems per 810.21." I say the Service Panel and MCCs are a structure and the grounding stystems should be connected per 810.21. What do you think? Not that I will change the PE's mind but just want a second opinion.
Thanks
 

tom baker

First Chief Moderator
Staff member
I have installed antennas at some 40 SCADA sites, orginally I was not clear on the grounding, but in my review of the code rules some 10 years ago, I determined that a code proposal was needed to 810.21, I made it and it was accepted.

It is very important to establish a single point ground for radio systems, to keep all equipment at the same potential. Its for this reason that the Intersystem Bonding Termination requirement was set up in the 2008 NEC.

Failure to do so may cause a lighting energy to travel to ground thru your SCADA radio...

I use a 2" water pipe mast, run the coax down thru the inside and into the building via a 2" c conduit body. At the base of the water pipe, I install a ground rod, with a 2 AWG cad welded to the ground rod and mast. From this 2 AWG I run over to the building electrical ground system. I enter into the building with coax, and hit a Polyphase impuse supressor, mounted on a insuated bus bar. From the bus bar, a 2 AWG copper goes back outside to the 2AWG and is cad welded to it.

A point often missed is the coax inside the building needs to be fire retardant, this change over is made at the impulse suppressor.

Since I often use a 20 ft mast, the mast has a hinged base and I have a boat winch I can attach to lower it down with a battery drill.


Ask your PE if he understands the reason why the intersystem bonding termination requirement was added, and if that provision is provided on the Well Electrical service as required by the 2008 NEC....

Most antennas I see for W/WW Scada sites are done wrong. A common error is to put the impulse supressor at the SCADA equipment cabinet.

Take a look at a cell site, they use single point grounding....

PM me with your email address and I will send you some detail drawings.
 

walton

Member
Location
Sacramento, CA
Thanks Tom,

I have done a number of SCADA site also and always tied the antenna grounding to the structure's grounding system (intersystem bonding). In this case there are no buildings on these SCADA sites. Just Electrical Service Panels and MCCs for pump control. The PE is saying there is no building so no intersystem bonding is required. He is confusing the term structure to mean building. I would call the Service Panel and MCC a structure per NEC definition.
I will ask the PE once more if the SCADA sites are following 810.21 and refer him to the Intersystem Bonding Termination requirements. I am not an Engineer just a Supervising Inspector so the PE has the last say. It's his design. Thanks again for the backup.

John
 

ceb58

Senior Member
Location
Raeford, NC
Thanks Tom,

I have done a number of SCADA site also and always tied the antenna grounding to the structure's grounding system (intersystem bonding). In this case there are no buildings on these SCADA sites. Just Electrical Service Panels and MCCs for pump control. The PE is saying there is no building so no intersystem bonding is required. He is confusing the term structure to mean building. I would call the Service Panel and MCC a structure per NEC definition.
I will ask the PE once more if the SCADA sites are following 810.21 and refer him to the Intersystem Bonding Termination requirements. I am not an Engineer just a Supervising Inspector so the PE has the last say. It's his design. Thanks again for the backup.

John

Also have him look at Motorola's R-56 grounding guide lines. They plainly state that a single point system is required, as Tom has mentioned.
 

sparky=t

Senior Member
Location
Colorado
I looked a three sites last week where the engineer had callled for a ground ring witrh 1/0 cu boding all metal to include gen set, contractor left gen sets un connected to ring.
 

walton

Member
Location
Sacramento, CA
I went back to the PE with the 810.21 issue. He says that "He doesn't consider the SCADA sites to be receiving stations" so therefore 810.21 does not apply. SCADA is a receiving and sending station! Very frustrating. I think this is one of those cases where the PE doesn't want his design second guessed by a lowey Inspector.

Thanks forum for all your input. At least I know I'm right, this time...
 

walton

Member
Location
Sacramento, CA
Thanks Tom

Thanks Tom

Because of the forum's input the SCADA station antennas are being bonded to the electrical services grounding system. A #6 bare cu is being installed from the antenna's ground lug to the service ground bus.
Thanks, especially to Tom Baker. The flash over link did it. The Water Agency over road the PE.
 

WIMaster

Senior Member
Location
Wisconsin
Because of the forum's input the SCADA station antennas are being bonded to the electrical services grounding system. A #6 bare cu is being installed from the antenna's ground lug to the service ground bus.
Thanks, especially to Tom Baker. The flash over link did it. The Water Agency over road the PE.

Glad to hear it!
 
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