Deep Earth Ground

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ed downey

ed downey

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I am working on a Performing Arts Center that the engineer is calling for us to use a Deep Earth Ground (which basically means we will drill 250' deep holes for ground rods). they are specifying that we have 3 ohms or less (Basically the Sound consultant is requiring the 3 ohms or less).

My question is what are the pro's and cons of this type of system (besides the huge cost)?

Have you heard of anything else that would work as well?

Any thoughts or reading material would be appreciated.

-Ed
 
Based on the above, IMHO the 'pro' is that hopefully you get paid a pile to do it. The 'con' (man) is that sound consultant. I can't see how it will make a bit of difference to the sound system unless maybe there's a honkin' big AM radio transmitter on top of the theater.

Not that I have a strong opinion about most sound and theater consultants :grin:... (I've had drawings that had the mic junction box on one side of the stage piped to the speaker junction on the other. Good thing -someone- was reviewing those drawings before installation. Caught quite a few of that sort of error on that project.)

I suppose it might mean better lightning protection, but I barely know squat about that.
 
ed downey said:
they are specifying that we have 3 ohms or less (Basically the Sound consultant is requiring the 3 ohms or less).
-Ed
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What size wire are you using to go down to the 250' deep ground rod? The wire itself will probably have a resistance of 3+ ohms.
 
I'm assuming they are going to have a load of communication devices and electronics if they trying to get 3 ohms or less--which is not unusual.
They have done of number of studies, and found that deep earth grounding was one of the best solutions for low resistive earth grounding, this may be the reason behind their request.

I would google: Deep Earth Grounding

I'm sure others will tune-in with more information.
 
What a waste of time, effort, and natural resources.

And 250' is absolutely ridiculus. Are you sure it's not 25.0' ?

I would certianly suggest other more conventional methods of grounding the systems as they are ALL that is necessary for any function they could hope to get from the grounding system.

If the onwer and sound consultant wnat to spend a bunch of money, I would sell them on surge protection and other conventional lightning protection verses crazy grounding schemes.
 
zbang said:
Based on the above, IMHO the 'pro' is that hopefully you get paid a pile to do it. The 'con' (man) is that sound consultant. I can't see how it will make a bit of difference to the sound system unless maybe there's a honkin' big AM radio transmitter on top of the theater.

Not that I have a strong opinion about most sound and theater consultants :grin:... (I've had drawings that had the mic junction box on one side of the stage piped to the speaker junction on the other. Good thing -someone- was reviewing those drawings before installation. Caught quite a few of that sort of error on that project.)
Click to expand...

This past Summer I helped my son run new speaker wires, in conduit, in a theatrical theatre. They have had issues with a local radio station coming through the sound system, some 20+yrs. So far this new install has eliminated the radio interference.

Edited to reflect correct Quote.
 
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Time and again I run into the "SOUND" guy and their creative "?engineering?".

Just did an inspection they had a TRUELY isolated system separate XIT ground electrode separate conductors, separate MGB's, separate everything, then at the critical loads they tied the two together (by accident I do believe).

I write my letters of explanations explaining the hows and whys the rights and wrongs..Oh the electrical inspector was suitable impressed that they kept the two systems isolated.

But if it meets code and they are wiling to pay for it Deep Eart Grounding has been proven to be effective.

http://www.cpccorp.com/deep.htm
 
An why not............I have seen more copper thrown at attempts to make the PERFECT VOODOO ground system than I make in a few life times.

Dig a 250' hole tie 4/0 to the SOUND GUYS belt loops and a swift kick in the.....

An engineer once told me all his jobs used a major manufacturer's ground electrode, with bentonite, drilled etc prior to using this system they had several recording facilities sustain lightning damage, since switching to this manufacture electrode no lighting issues. Science or LUCK? I'd bet if you talk the owners out of this SUPER electrode and the facility takes a hit...They'll point the fickle finger of faith at YOU.
 
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This article also states that my 2 8 foot ground rods violate code.:mad:

They are very proud of 1 ohm.... What is the resistance of the source (roughly)? Basically, what is the resistance of a piece of copper?
 
Brian John I have read the article and IMO it is bogus and void of facts. I design low impedance grounding systems for a living for telecom and data, and there is no substance to what is being said here in the paper you pointed too. Some examples and comments:

“Effective earth grounding is essential for grounded AC and DC electrical equipment and distribution systems. Effective grounding provides the level of safety required to protect personnel and equipment from shock and fire hazard”

Earth grounding has very little if anything to do with safety and protection of personnel and equipment fire hazards. That is the job of bonding and EGC’s.

“In order to understand earth grounding and test procedures, it is necessary to review why grounding is important. The list below gives some of the basic requirements of an effective ground system.

  • limits voltage in a electrical distribution system to definite fixed values
  • limits voltage to within insulation ratings
  • provides a more stable system with a minimum of transient over voltage and electrical noise
  • provides a path to ground in fault conditions for quick isolation of equipment with operation of ground fault protection
  • provides grounding of all conductive enclosures that may be touched by personnel, thereby eliminating shock hazards
  • reduces static electricity that may be generated within facilities
  • provides protection from large electrical disturbances (such as lightning) by creating a low resistive path to earth

Again this has little to do with earth and the impedance to earth is of no real importance. It is the bonding and EGC job to accomplish the above.


“According to the IEEE Green Book [3], the grounding electrode resistance of large electrical substations should be 1 Ohm or less. For commercial and industrial substations the recommended ground resistance is 2-5 Ohms or less. This low resistance is required due to the high potential to earth of the electrical system.

Completely true statement but taken out of context. Electrical Substations are high voltage environments that use earth as a conductor. NEC forbids the earth to be used as any type of conductor.

OK, I am sure by now some of you may be asking yourself: Then why do jerks like me specify low impedance earth system? It is a good question which I will answer. Because we do not want to leave it to the discretion of the electrician to meet code minimum of driving two rods in the ground using the least expensive mechanical connector you can get your hands on and bury it where it will never been seen again.
 
SmithBuilt said:
That's disturbing to know.
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Been that way since Edison built the first system. All Poco's use earth for the unblalnced loads for a variety of reasons, one being cost. Dirt is a lot cheaper and lower resistance than miles of copper, steel, and aluminum.

One of The primary reasons you have an earth electrode at your home or biz is to operate the POCO's fuse operating at high voltages in the even of accidental primary to seconary contact. Utilities work under NESC rules as opposed to NEC for the lower voltage applications.

As stated it has to do with Ohm's Law.
 
andinator said:
Isn't a fuse on a sub-station surprisingly low?
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Not exactly, they don't use fuses in substations per se, they use protective relaying and high-speed air or gas operated switches.
 
andinator said:
No it's not. Use OHMS law. The higher the voltage, the lower the amperage.
Isn't a fuse on a sub-station surprisingly low?
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Thats incorrect. For a fixed resistance Ohms law says the higher the voltage the higher the current. I = E/R . For a 22.4 kva sub at 115 kv the FLA = 113 amps. Fuse ~ 200 amps.
dereckbc
We had a number of 115 kv subs with fuses.
 
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Pierre C Belarge said:
He may be thinking of the fuses at tranformers for distribution, some are sized at 5 amps (I believe).
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He might have, I was just responding to the way it was worded. However you are correct distribution transformers are low amperage fuses.
 
bob said:
... For a 22.4 kva sub at 115 kv the FLA = 113 amps. Fuse ~ 200 amps. ...
Click to expand...

I suspect you meant 22.4MVA

bob said:
...For a fixed resistance Ohms law says the higher the voltage the higher the current. I = E/R . ...
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I suspect the meaning was, "For a fixed power, the higher the voltage the lower the current." But I'm guessing you already knew that.

carl
 
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