Different phase to ground voltage readings

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GoldDigger said:
Your argument that conductance goes to zero as distance increases is analogous as saying that if you travel at one meter per second the distance goes to zero as time increases. :angel:
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I think you know that analogy doesn't hold water............:)
 
Besoeker said:
OK. What's the distinction between earth and ground?
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Definitions from NEC:
Ground.
The earth.


Ground Fault.
An unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non–current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.


Grounded (Grounding).
Connected (connecting) to ground or to a conductive body that extends the ground connection.


Grounded, Solidly.
Connected to ground without inserting any resistor or impedance device.


Grounded Conductor.
A system or circuit conductor that is intentionally grounded.


Ground-Fault Current Path.
An electrically conductive path from the point of a ground fault on a wiring system through normally non–current-carrying conductors, equipment, or the earth to the electrical supply source.
Informational Note: Examples of ground-fault current paths are any combination of equipment grounding conductors, metallic raceways, metallic cable sheaths, electrical equipment, and any other electrically conductive material such as metal, water, and gas piping; steel framing members; stucco mesh; metal ducting; reinforcing steel; shields of communications cables; and the earth itself.


Grounding Conductor, Equipment (EGC).
The conductive path(s) that provides a ground-fault current path and connects^ normally non–current-carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.
Informational Note No. 1: It is recognized that the equipment grounding conductor also performs bonding.
Informational Note No. 2: See 250.118 for a list of acceptable equipment grounding conductors.


Grounding Electrode.
A conducting object through which a direct connection to earth is established.


Grounding Electrode Conductor.
A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.
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Then there is "bonding", and several terms that include the word "bond" somehow.

Gets kind of tricky wading through some of these terms as they often are all dealing with a conductor that is connected to earth in some way, but the specific function of a some terms isn't always "earthing".
 
Besoeker said:
OK. What's the distinction between earth and ground?
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I'll lose in a battle of wits, but here is my take on this.

Earth is what we stand on or swim in and as far as the electrical systems I work with it means little until I make a connection to it. Purposely or by accident. Ignoring lightning or static charges.

'Ground' is developed after I make a connection to my electrical system. Building steel, hull of boat, metal frame of a vehicle, or the floating oil platform. None of them require a connection to earth to operate.

My flashlight works quite fine without a connection to earth. Taking a Voltage reading between it and earth is meaningless.

my spouse has paged...
 
ptonsparky said:
I'll lose in a battle of wits, but here is my take on this.

Earth is what we stand on or swim in and as far as the electrical systems I work with it means little until I make a connection to it. Purposely or by accident. Ignoring lightning or static charges.

'Ground' is developed after I make a connection to my electrical system. Building steel, hull of boat, metal frame of a vehicle, or the floating oil platform. None of them require a connection to earth to operate.

My flashlight works quite fine without a connection to earth. Taking a Voltage reading between it and earth is meaningless.
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Good stuff right there. I agree.
my spouse has paged...
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Good luck.
 
ptonsparky said:
I'll lose in a battle of wits, but here is my take on this.

Earth is what we stand on or swim in and as far as the electrical systems I work with it means little until I make a connection to it. Purposely or by accident. Ignoring lightning or static charges.

'Ground' is developed after I make a connection to my electrical system. Building steel, hull of boat, metal frame of a vehicle, or the floating oil platform. None of them require a connection to earth to operate.

My flashlight works quite fine without a connection to earth. Taking a Voltage reading between it and earth is meaningless.

my spouse has paged...
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Look at the NEC definitions given by kwired in post #68. The first one.
 
Besoeker said:
Ground.
The earth.

That's the definition.
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Please, try to help me out.

What does any of that have to do with the OPs issue?

The issue in this thread has nothing to do with Earth or the dirt it is made from. Yes, the NEC is a mess of terms, grounding, bonding grounded etc. Often at least as messed up as inches pounds and gallons :D but we understand it.

It seems you are having a hard time in this thread because you do not work with the NEC.

Consider this, even an NEC ungrounded source will require grounding electrodes.
 
iwire said:
Please, try to help me out.

What does any of that have to do with the OPs issue?
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He mistakenly thought he was measuring to ground or take it as earth from the NEC definitions

iwire said:
The issue in this thread has nothing to do with Earth or the dirt it is made from. Yes, the NEC is a mess of terms, grounding, bonding grounded etc. Often at least as messed up as inches pounds and gallons :D but we understand it.

It seems you are having a hard time in this thread because you do not work with the NEC.
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As you accepted in an earlier post, we don't know if the NEC is applicable on an offshore rig.
 
Besoeker said:
He mistakenly thought he was measuring to ground or take it as earth from the NEC definitions
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For those that work with NEC all the time, we probably just assume he meant he was measuring to the equipment grounding conductor, and if installed correctly does have an earth connection somewhere at some electrode.

Most of us do not measure to earth unless we are trying to resolve stray voltage issues, when we are just taking general measurements to see if voltage is in the expected range - we measure between all ungrounded conductors, to neutral conductors (which usually are required to be grounded), and to the equipment grounding conductor. If you don't have proper bond between grounded and equipment grounding conductor on a system that is supposed to be grounded you may have some unexpected voltages between them, which appears to be exactly what has happened in the OP's application.
 
Besoeker said:
He mistakenly thought he was measuring to ground or take it as earth from the NEC definitions.
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Again this goes back to you not being an electrician here

When a fellow electrician says to me he measured line to ground or more commonly 'hot to ground' they are measuring from line to some grounded metal object. They do not mean earth.

Before you explain to me how that does not match the NEC definition I will tell you I know that. It's called slang and those of us here understand that.
 
don_resqcapt19 said:
But that value is really the resistance of the connection between the electrode and the earth...it is not the resistance of the earth.
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So, I want to check my understanding here: when we say that the earth itself has 0 resistance, and all of the resistance is due to the connection between the grounding electrode and earth, does that mean the following:

Say we have 4 widely spaced grounding electrodes, and we carefully measure the resistance between each pair of electrodes, accounting for all other sources of resistances in the measurement. There are 6 pairs of electrodes, so we come up with 6 measurements. What we find is that those 6 measurements will follow a pattern: we can assign a resistance to each of the grounding electrodes, and the measured resistance between any pair of electrodes will just be the sum of the of the 2 electrode resistances. There won't be any discrepancy requiring an additional term attributable to the "resistance of the earth itself". Repeating the experiment with the 4 electrodes spaced much more widely apart won't show any additional discrepancy from the pattern.

Is that right?

I picked 4 above as it is the smallest number where the number of pairs exceeds the number of electrodes. E.g. with 3 electrodes, there are just 3 measurements, so the math says the pattern always works.

Cheers, Wayne
 
iwire said:
Again this goes back to you not being an electrician here

When a fellow electrician says to me he measured line to ground or more commonly 'hot to ground' they are measuring from line to some grounded metal object. They do not mean earth.

Before you explain to me how that does not match the NEC definition I will tell you I know that. It's called slang and those of us here understand that.
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With respect, unless/until we know that the NEC is applicable for this application, any explanation is somewhat irrelevant.
 
wwhitney said:
So, I want to check my understanding here: when we say that the earth itself has 0 resistance, and all of the resistance is due to the connection between the grounding electrode and earth, does that mean the following:

Say we have 4 widely spaced grounding electrodes, and we carefully measure the resistance between each pair of electrodes, accounting for all other sources of resistances in the measurement. There are 6 pairs of electrodes, so we come up with 6 measurements. What we find is that those 6 measurements will follow a pattern: we can assign a resistance to each of the grounding electrodes, and the measured resistance between any pair of electrodes will just be the sum of the of the 2 electrode resistances. There won't be any discrepancy requiring an additional term attributable to the "resistance of the earth itself". Repeating the experiment with the 4 electrodes spaced much more widely apart won't show any additional discrepancy from the pattern.

Is that right?

I picked 4 above as it is the smallest number where the number of pairs exceeds the number of electrodes. E.g. with 3 electrodes, there are just 3 measurements, so the math says the pattern always works.

Cheers, Wayne
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It will be different as you have moved the rods and the rod to earth connection will not be the same.
 
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