Equipment Grounding for Ungrounded System

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buckofdurham said:
2008 Soare's Book on Grounding and Bonding 10th addition.


Have you ever installed an electric fence for animals?
You have to put two ground rods in at every thirteen hundred feet with the grd. wire attached. It's amazing that the electrons will travel through the animal back to the source.
It is reccomended if the soil is real dry. To moisten the soil.
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We have installed a substation.
 
buckofdurham said:
It is reccomended if the soil is real dry. To moisten the soil.
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This is also true if we want to give unrealistic values to fall of potential ground test reports. As a matter of fact, I can salt these soils for more of a false value, so what's your point?

Roger
 
bobby ocampo said:
If by standing near to the connection to the ground may reduce the electric shock hazard then it means that connection to the earth is also as important as compared if it is not connected to the earth. However It is also as important to bond the EGC to trip the OCPD in a solidly grounded system and Low resistance grounded system due to arc flash hazard if one of the current carrying conductor will accidentaly or intentionaly touch a non conducting metal part due to a single line to ground fault. Bonding EGC is also important to have equipotential to all the bonded metal piece in the system and the ground.

Again BOTH should be important. Bonding and and connection to ground. Saying that they have relative importance is hazardous.
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You're still hung up on the connection to earth/dirt, aren't you? Not a single person in this entire thread has suggested that we shouldn't connect to the earth because there are valid reasons for doing so with premises wiring system voltages. However, facilitating the operation of OCDP and reducing touch potential are not of of those reasons we connect to earth. We are simply pointing out that connecting to earth has very limited value at 600 volts systems and under.

We connect to earth primarily for accidental contact with higher voltages, as well as lighting protection.
 
roger said:
What is the voltage in this substation?

Roger
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Mostly 34.5kv primary to 480Y/277 volts secondary with some 208Y/120 volts secondary solidly grounded system.

Some are also 13200 volts primary to 240Y/139 volts or 208Y/120 volts secondary
 
bobby ocampo said:
Mostly 34.5kv primary to 480Y/277 volts secondary with some 208Y/120 volts secondary solidly grounded system.

Some are also 13200 volts primary to 240Y/139 volts or 208Y/120 volts secondary
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And this is where the difference lies, on the primary side your concerns and views are real and justified, on the secondary side (using your voltages) we have a much different reason for earthing a system.

Roger
 
roger said:
And this is where the difference lies, on the primary side your concerns and views are real and justified, on the secondary side (using your voltages) we have a much different reason for earthing a system.

Roger
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This would have been so much easier if he only mentioned that in the beginning. :roll: ;)
 
bobby ocampo said:
Again, Both should be done. Both connection to earth and bonding EGC. If there are many incidents of people grounded in poles and manholes a grounding mat bonded and connected to earth should be installed.
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An EGC should be used, a grounding mat only moves the hazard to another location. The complete mat will be energized and the shock hazard will no longer be at the pole, but at the edge of the mat. With the steep change in potential as you move a few feet away from the grounding electrode will create a hazardous step potential at the edge of the mat.

Another solution to reduce arc flash hazard is using High Resistance Grounded but use line-to-line voltage not line-to-neutral voltage. There is NO arc flash hazard in a High Resistance Grounded system on a single-line-to-ground fault. Electic shock hazard is also reduced if EGC is bonded and connected to earth. Both are important.
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Like I have said a number of times, the use of systems other than solidly grounded systems is not permitted for most of the loads that most electricians will work on. A change to other types systems to reduce the hazard just is not an option for most.
 
don_resqcapt19 said:
An EGC should be used, a grounding mat only moves the hazard to another location. The complete mat will be energized and the shock hazard will no longer be at the pole, but at the edge of the mat. With the steep change in potential as you move a few feet away from the grounding electrode will create a hazardous step potential at the edge of the mat.
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Then you can use the solution done in most substation.

don_resqcapt19 said:
Like I have said a number of times, the use of systems other than solidly grounded systems is not permitted for most of the loads that most electricians will work on. A change to other types systems to reduce the hazard just is not an option for most.
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Then maybe most electricians may start studying the possibility of using other grounding system which may be safer than solidly grounded.
 
roger said:
And this is where the difference lies, on the primary side your concerns and views are real and justified, on the secondary side (using your voltages) we have a much different reason for earthing a system.

Roger
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Grounding the low voltage side is what makes it solidly grounded system. Not the primary side.
 
bobby ocampo said:
Grounding the low voltage side is what makes it solidly grounded system. Not the primary side.
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And there is no question that this is the case, but what you seem to think it achieves (or at least what I think you are saying it achieves) is not the same as what it does for an MV or HV system.


Roger
 
bobby ocampo said:
We have installed a substation.
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Just a suggestion, when the discussion is about electric fences, stick to fences, substations really don't apply.

it would make your discussions a lot easier to follow.

carl
 
bobby ocampo said:
Sorry Sir don't understand what you mean that IEEE and NEC don't always do a real good job. ...
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bobby 0 -

Others have already said this: Historically the NEC has used the term "grounding" when they meant "bonding". Bonding provides the low impedance path that allows faults to trip CBs. These faults are called "ground faults" but they don't have any thing to do with "ground" or "earth". The faults being discussed are to the non-current carrying metal parts - not earth.

Historically the IEEE has not done much better. However, they are coming around. At least now, the IEEE defines the equipment grounding system separating equipment bonding from equipment grounding - and notes the bonding is what trips the breakers.

Let me give an example: You use the term "EGC" - "equipment grounding conductor". Sometimes the context is "bonding the non-current carrying parts" and sometimes the contest is a connection to a ground rod. As has been said, too bad we don't use the term EBC for bonding, and EGC for connection to a ground rod. It would certainly make your discussion easier to follow.

carl
 
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bobby ocampo said:
Then you can use the solution done in most substation.
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Again, all that does is move the hazard to the edge of the grounding mat. It makes it relatively safe for workers in the substation but creates a step potential hazard at the edge of the mat.

Then maybe most electricians may start studying the possibility of using other grounding system which may be safer than solidly grounded.
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Why? We cannot use those other systems for line to neutral loads and I don't thing we will ever get rid of line to neutral loads. If and when we start moving to eliminate line to neutral loads, then it would be time for most electricians to start learning about them. As it stands now, the majority of electricians will never see a HRG or LRG system outside of a text book or a forum like this.
 
Bobby,
Lets start back at the beginning. With a correctly installed solidly grounded system with no faults, exactly how does a connection to earth make that system safer?
 
Hello


I think the residential Electrical system needs to be earthed or solidly grounded to the earth with a grounding Electrode to earth.

Because, lets say we go with a system which has a floating grounding conductor system which is not earthed.All metal equipment and
construction materials are grounded to the grounding system which is floating or insulated from the earth.This has to be required to clear
faults to trip the breakers.

We are required by code to have outlets outside at front and back for outside work. We know the GFI probably want work since
the system is not earth.

Example of why and this is just one reason.

We have an extension cord plugged in for a hedge clipper and this clipper receptacle is on line #1.
If this extension cord had a nick of exposed wire on the hot side of the line #1 and was touching the wet ground
nothing would happen you would never know that the ground around you was energized, until you touched your in this case
aluminum siding on your house and received a fatal shock.

There are other reasons but this is the most simple to understand.

The worst thing I think about earthing a system is that the grounded high tension line has a direct connection to your neutral
that feeds your house.

I agree with Don that we do need this jumper for clearing high voltage faults where a high tension line falls onto one of your 240 volt
residential electrical system. :)
 
ronald -
I not sure I understand exactly what you are saying - here's why:
ronaldrc said:
...Because, lets say we go with a system which has a "floating grounding conductor system which is not earthed. All metal equipment and construction materials are grounded to the grounding system which is floating or insulated from the earth. This has to be required to clear faults to trip the breakers.
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"floating grounding conductor system which is not earthed" doesn't make much sense. I suspect the NEC and IEEE practice of using the term "grounding" when they mean "bonding" has me slowed down. If you meant "bonded" and "bonding" then a line to equipment or structure (all bonded) bonding conductor will trip the cb to clear a fault. A connection really doesn't make any difference - doesn't help, doesn't hinder.

ronaldrc said:
... We know the GFI probably want work since
the system is not earth.

Example of why and this is just one reason.

We have an extension cord plugged in for a hedge clipper and this clipper receptacle is on line #1.
If this extension cord had a nick of exposed wire on the hot side of the line #1 and was touching the wet ground
nothing would happen you would never know that the ground around you was energized, until you touched your in this case
aluminum siding on your house and received a fatal shock. ...
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This is similar to Larry's post about GFCIs and I get stuck here. My inclination is that the GFCI works on Summation (I) = 0 or what goes out comes back on the other conductor - or the GFCI trips.

My brain says, "How do you know this is true for capacitive phase shifted currents?" I suspect that any current imbalance in the 4-6ma range will cause a trip, but I have not seen any peer reviewed papers or tests on this.

What this means is if I'm right, then any current (at least 4-6ma), capacitive phase shifted of not, that will shock you, will cause a gfci trip - EBC connected to neutral or not,
neutral connected to ground or not

got to go for now. Maybe we can discuss the HV dropped on house service later.

carl
 
Carl

I just assumed that when a few on here are talking about doing away with the earthed ground they are just talking about the earth ground electrode.

You sure can't do away with the entire grounding system if you did why would you need a service panel with overcurrent protection?

There would be no way to clear faults. :)
 
Carl

I agree with Larry without a earth ground there would not be enough current flowing around the CT. of the GFI receptacle even in damp conditions.

It would be in the microamps. :)
 
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