What's a Counterpoise? 3

[NAZ55]

Does anyone have any information on what a counterpoise is?

 

[rbulsara]

In the electrical world of the USA, it is a grounding electride system consisting of three ground rods buried in ground roughly 10 feet apart from each other forming an triangle and connecting them with copper conductors.

 

[jghrist]

I'll have to differ. Counterpoise is a grounding electrode made up of buried wire, often used with transmission towers. "Continuous" counterpoise is sometimes used where the wire is buried continuously between towers.

 

[rbulsara]

jghrist:

That may also be correct. But commercial electrical contract drawings are on are full with so called standard grounding electrode details referred to as "counterpoise" as I described. It may or may not be appropirate but that is what most electrical contractors in commercial world understand.

It is possible that the term counterpoise is loosely applied there. As I undestand is "counterpoise" grounding electrode system has a closed loop versus radail conductors. Its roots possibly are in antenna grounding.

Question to OP is where did he/she find this term? What precipitated the question.

Here is a link that discusses "counterpoise".

http://www.antennex.com/shack/Dec06/cps.html

 

[Skogsgurra]

It may help if one knows how the word counterpoise was formed. It is French. And "Counter" means counter, exactly as in English. "Poise" means weight. So the word literally means "counterweight" and that is what a counterpoise is in an antenna system, where it was originally used. Simply put, a ground plane that the antenna system could "mirror" itself in.

The earth electrode configuration has been adopted by power industry and the name has been taken over without much thinking about its real meaning.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[NAZ55]

I have been told that a counterpoise may help with improving GPR? It would help if I know what a counterpoise is.

 

[NAZ55]

jghrist, what makes this counterpoise different from a typical ground grid? Is it just an underground ground connection between two transmission towers?

 

[jghrist]

Generally, counterpoise on a transmission tower is 4 radials extending out from the tower toward the edge of the ROW and down the line in either direction.

The term is as I defined it in the IEEE Green Book. A typical ground grid would be in a substation with closed meshes. Typically counterpoise would be used on a transmission tower, especially if it is hard to drive ground rods. I don't know how common it is. I've always just used ground rods or used the tower pier foundations as a ufer ground.

Gunnar's explanation of the origins sounds right to me. I expect that the term is used for many different kinds of grounding electrodes in different applications. Try Googling it.

Any grounding electrode will help reduce GPR and counterpoise by any definition is a grounding electrode (or earthing).

 

[NAZ55]

Thanks all. I appreciate your responses. jghrist thanks for clarifying the term for me. It makes a lot more sense now.

 

[cuky2000]

COUNTERPOISE "A conductor or system of conductors arranged beneath the line; located on, above, or most frequently below the surface of the earth; and connected to the grounding systems of the towers or poles supporting the transmission lines."

 

[pwrtran]

zazmat

A simple explanation - a counterpoise is an extension conductor that connects the main ground grid to a remote grid or a ground electrode. It typically runs along with a overhead line, e.g.skywire or ground wire, and it helps the main grid to dissipate a fualt current by parallelling more ground conductors to the grid, hence reduce the GPR.

 

[rbulsara]

This again is one example of common practices and names being accepted as definitions rather than starting out as a rule. In this IEEE definition there is no relavance to the term "counterpoise" or its meaning as gunnar indicated. It sounds like that the word counterpoise does come from antenna grounding practices and is loosely borrowed by power people.

 

[Bronzeado]

Hi folks,

Just to let you know on the use of the term "counterpoise" (in Portuguese is "contrapeso"), is common practice in my company (Chesf, Northeast of Brazil) to use "contrapeso" to improve transmission lines grounding, mainly those with concrete towers.

Regards,

Herivelto Bronzeado

 

[rbulsara]

Here is one example of how commonly this term is used (rightly or wrongly):

The follwing is excerpt from standard guide specs used for building systems. It does not mean that it is the definition but it is very commonly used and understood term by electrical contractors in the USA. It is a misapplied term in my opinion.

"COUNTERPOISE: Ground the steel framework of the building as shown on plans. Provide a grounding conductor (counterpoise), electrically connected to each ground rod and to each steel column, extending around the perimeter of the building. Use copper conductor not less than No. 4/0 AWG for counterpoise and for welding to building steel. Bury counterpoise not less than 18 inches (450 mm) below grade and 24 inches (600 mm) from building foundation."

 

[jghrist]

rbulsara,

So, as I read the requirement, this is what the NEC and NFPA 780 call a ground ring. NEC 250.53 (F) requires a ground ring to be 750 mm (30 in.) deep. You only need 18 in. (457 mm) according to NFPA 780 ¶3.13.3, so I guess your guide spec is OK if it is for the lightning protection system (if you're using a meter stick instead of a yard stick, you need an extra 7 mm);-), but not if it is for the electrical power system.

I have seen a substation construction specification that uses the term counterpoise for the wires in a station ground grid.

 

[rbulsara]

jghrist:

Inches to mm conversion factors are not mine! -. The are in so called master specs. Thank US government for that or whosover thought of converting US to metric!! They are mandatory now in US Govt. specs (I stay away from Govt. work for the record.)

Yes, the word "ring" or "closed loop" is the key. Since that kind of mimics the topology of a true counterpoise antenna grounding grid, perhaps the term 'counterpoise' was borrowed by some power (more likely the Tower people, who would be the common link between the antenna work and the power work).

 

[waross]

My understanding is that a ground ring or grounding system was intended to provide a low resistance contact to earth.
I always understood that a "counter-poise" was intended to improve the radiation characteristics of a radio transmission tower or antenna.
I would consider conductors radiating out from the base of an AM transmission tower to be a counter poise, as they affect the transmission of the signal.
I would consider the grid or ring around the base of a tower supporting cell phone antennas or something similar to be a ground grid or ground ring, as they are for safety grounding and intended primarily to limit touch and step potentials. The grounding has little or no effect on the radiated signal.
I believe that this distinction was valid years ago, but has been blured over the years by popular misusage.

Bill
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"Why not the best?"
Jimmy Carter