# sparking ground wire...



## waco (Dec 10, 2007)

I have on occasion had a grounding wire spark when it was disconnected, but the event didn't signal a problem in the electrical system, but the operation of a cable or telephone system which was using that ground. The spark was more of an arc and barely visible even in a dark basement.

I think even professionals should recognize the difference between a slight arc and the serious sparking one would see if the neutral was open, not to mention the electrical shock one would get when the ground wire was lifted from the clamp.

I think single point grounding is one of the best changes recently made to the code because it makes events like the one in that post far easier to understand -- even for professionals.


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## Mr 440 (Nov 10, 2008)

Balancing the phase panel 
suppose 3 phase 
10 10 10 neutral =0

suppose 
10 20 30 neutral =5/8

switch the load egal phase egal amps 
after no spark a the ground.


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## leland (Dec 28, 2007)

If you get 'sparks/arcs off of your ground, you have a problem.
It is not a Current carrying conductor. .(period)


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## brian john (Mar 11, 2007)

Mr 440 said:


> Balancing the phase panel
> suppose 3 phase
> 10 10 10 neutral =0
> 
> ...


A balanced load HAS NOTHING to due with whether there is a wiring issue that will result in current on a EGC. Now when the load is balanced no current will flow on the EGC BUT a balanced load DOES NOT RESOLVE THE ISSUE that leads to a sparking EGC.

IF A=10, B=20 , C=30 then neutral = 17.5


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## ACB (Oct 21, 2008)

is the spark occuring on a ground wire from a circuit ground or the main ground (to the ground rod or water pipe)?


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## bigredc222 (Oct 23, 2007)

It could just be something as simple as a difference in potential from the ground at the panel and the ground that the device in mounted on. If that's the case then there is no problem. 
Chris


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## bobelectric (Feb 24, 2007)

I amprobed a 1200 amp,3 phase 208 volt g.e.c. to waterline and the amprobe showed 5 amps.Three story office building.I reasoned it was from harmonics from all the computers.


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## randomkiller (Sep 28, 2007)

bobelectric said:


> I amprobed a 1200 amp,3 phase 208 volt g.e.c. to waterline and the amprobe showed 5 amps.Three story office building.I reasoned it was from harmonics from all the computers.


I have never had a reason to take a reading from a GEC,
so I have nothing to compare it to but 5 amps still sounds high for harmonics, no?


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## bobelectric (Feb 24, 2007)

Marine, I just did that as a prelude to a power quality study .I thought that was strange,checked neutrals, balanced computer room panel,still 5 amps.(checked neutral even at xfmr).


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## JohnJ0906 (Jan 22, 2007)

Remember, the utility's transformer is grounded, and so is the service entrance. The earth will provide a parallel path for neutral current - the amount depends on the resistance of the earth.


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## waco (Dec 10, 2007)

It is true, in a perfect world the grounding wire doesn't carry current, but other systems use that same grounding and we really can't make assumptions about how they manage their current flow.

What I do know is that a neutral fault would probably be far more dramatic than sparking when one ground connection is opened. Of course, theory and reality can be two different things, so we all need to be careful in our actions and assumptions.


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## brian john (Mar 11, 2007)

bigredc222 said:


> It could just be something as simple as a difference in potential from the ground at the panel and the ground that the device in mounted on. If that's the case then there is no problem.
> Chris



Wrong




> I amprobed a 1200 amp,3 phase 208 volt g.e.c. to waterline and the amprobe showed 5 amps.Three story office building.I reasoned it was from harmonics from all the computers.


Wrong

In any system of substantial size there will be leakage current from the insulation this leakage current is typically in the 1-20 amp range depending on the size of the distribution system, type of loads (large cap banks) ect....

In any case where there is measurable current the neutral should be isolated from the system and meggered for possible shorts to ground.
The number one cause of ground current is a short on the neutral downstream from the main neutral to ground bond.


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## bigredc222 (Oct 23, 2007)

I don't believe he said he had measurable current. He said he had a little arc. Are you saying there is never a spark caused by a difference in potential?


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## brian john (Mar 11, 2007)

ARC are Always caused by a different in potentials BUT the EGC should NEVER have a difference of potential BECAUSE under normal operation it will not have current or voltage on the EGC.


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## waco (Dec 10, 2007)

Yes, arcing and sparking is due to differences of potential, but that doesn't mean there's a problem.

I have encountered old buildings in which I measure the voltage from the panel ground to the grounding electrode pipes because I have suspected there might be a fault between the neutral and earth ground and if there was, the end of that ground wire would be too dangerous to handle, but I think any grounding system can see some current flow, even if only through induced voltages.

I just can't say with certainty that a ground wire can never have a potential relative to the grounded electrode. I just can't make that flat conclusion.


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## brian john (Mar 11, 2007)

waco said:


> I have encountered old buildings in which I measure the voltage from the panel ground to the grounding electrode pipes because I have suspected there might be a fault between the neutral and earth ground and if there was, the end of that ground wire would be too dangerous to handle, but I think any grounding system can see some current flow, even if only through induced voltages.
> 
> .


READ

In any system of substantial size there will be leakage current from the insulation this leakage current is typically in the 1-20 amp range depending on the size of the distribution system, type of loads (large cap banks) ect....


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## waco (Dec 10, 2007)

I agree, brian john and I think it should be noted that it is this "stray" voltage that requires the grounding system to be as low a resistance as possible. The lower the resistance, the less these voltages can develop.

But, as you point out, they are still there if the grounding system is disrupted.


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## bobelectric (Feb 24, 2007)

brian john said:


> ARC are Always caused by a different in potentials BUT the EGC should NEVER have a difference of potential BECAUSE under normal operation it will not have current or voltage on the EGC.


Tell that to the guys that replace water meters.


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## Golden Arc (Apr 28, 2008)

Is every thing bonded the main, and the transformers?


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## waco (Dec 10, 2007)

Tim Crimson said:


> Is every thing bonded the main, and the transformers?


I don't understand the question relative to the discussion. I'm thinking that even with bonding throughout the system, the EGC is still its own conductor until it gets back to the main panel/disconnect.

Am I missing something here?


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## brian john (Mar 11, 2007)

waco said:


> I don't understand the question relative to the discussion. I'm thinking that even with bonding throughout the system, the EGC is still its own conductor until it gets back to the main panel/disconnect.


TYpically everything is bonded the issue is that downstream from the MAIN neutral bond there are additional bonds. 

If everything was not bonded you would have an ungrounded system. With an ungrounded system you do not have issues with EGC currents that is until you bonded the neutral downstream from from the main service. And of course the NEC prohibits ungrounded systems utilizing a neutral.

Number one cause commercial of EGC current IS----Neutrals grounded downstream from the main neutral ground.

Number one cause in a residence IS where several houses are off the same transformer and have copper water pipe for water supply. Then you have multiple neutral bonds and the water pipe (or gas) carry some current.


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## wdestar (Jul 19, 2008)

*Grounding and Voltage Potential*

I would suspect that many would assume that ground is "ground"... period. And that's a dangerous assumption.

There remains voltage potential that one must consider. My response is vague by design - no liabilities assumed.


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## brian john (Mar 11, 2007)

Ground is ground but never assume anything, serious issues are simple to avoid, amp clamp and multimeter to the rescue.


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## bobelectric (Feb 24, 2007)

And then, why did I measure 5 amps on the wire connected to the water line?


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## brian john (Mar 11, 2007)

Bob have you been following the thread?

*Number one cause commercial of EGC current IS----Neutrals grounded downstream from the main neutral ground.

Number one cause in a residence IS where several houses are off the same transformer and have copper water pipe for water supply. Then you have multiple neutral bonds and the water pipe (or gas) carry some current.*


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## wdestar (Jul 19, 2008)

*Naive at First*

When I was young, I thought I knew much - not unlike many in this forum.

I was wrong. I didn't know half as much as the elders - I just had a chip on my shoulder.

So, for what it's worth - if you're young ... don't take your talents too seriously... and if you're older, it' not too late to retire.

Dan


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## waco (Dec 10, 2007)

Grounding of neutrals "downstream" does create parallel paths and confuse the circuit theory, but I'm still firm on the idea that minor sparking at the grounding terminal doesn't necessarily signal a problem, although it could.

I agree with wdestar, I think the longer we work in the field, the more we are forced to deal with our assumptions we found so comforting when we were younger.


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## nolabama (Oct 3, 2007)

if the spark is caused by more than .07 amps it can be a real problem


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## waco (Dec 10, 2007)

Let's see now. Amps are caused by voltage and sparks are caused when voltages come into close enough contact to create amps, so I assume the point is, a voltage that remains high enough to cause seven hundreths of an amp when the ground contact is made indicates a problem. I honestly don't know. That's about 3.5 millivolts into a 20 ohm ground.


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## nolabama (Oct 3, 2007)

waco said:


> Amps are caused by voltage and sparks are caused when voltages come into close enough contact to create amps, so I assume the point is, a voltage that remains high enough to cause seven hundreths of an amp when the ground contact is made indicates a problem. I honestly don't know. That's about 3.5 millivolts into a 20 ohm ground.


i confuse easily, please explain your response


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## nolabama (Oct 3, 2007)

spark = an electrical discharge caused when electric current through an inductive device such as an electric motor is suddenly interrupted, e.g. by a switch 

current = The SI unit of electric current intensity is the ampere. Electric current is measured using an ammeter.

A low-voltage (110 to 220 V), 50 or 60-Hz AC current through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 mA. With DC, 300 to 500 mA is required. If the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode), a much lower current of less than 1 mA, (AC or DC) can cause fibrillation. Fibrillations are usually lethal because all the heart muscle cells move independently. Above 200 mA, muscle contractions are so strong that the heart muscles cannot move at all.

so woopee i can use wiki and cut and paste - but the root of my problem is the grounding conductor has a leathal potential so i cannont see were a sparking ground wire is ever a good thing - some research must be given to this problem to correct what could be a potentially leathal problem - if i am wrong please tell me were - i just cannont understand when and were current on a grounding conductor should be tolerated

oh wait i can see were current can be tolerated - when clearing a fault
other than that ?


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## waco (Dec 10, 2007)

Confuse easily? So do I.

That's a pretty low voltage to be considered significant, which is why grounding systems are supposed to be the very lowest resistance we can get -- low resistance offers nothing for voltage be develop over.

Sparks happen anything current is interrupted.

Problem with being dangerous is that our skin presents a heckuva lot more resistance than 20 ohms. Go ahead, measure the resistance between your hands or even between two fingers on the same hand.


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## brian john (Mar 11, 2007)

wdestar said:


> When I was young, I thought I knew much - not unlike many in this forum.
> 
> I was wrong. I didn't know half as much as the elders - I just had a chip on my shoulder.
> 
> ...


 I have neither problem I know what I know and what I do not know I investigate to learn more about my profession.


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## BP_redbear (Jun 22, 2008)

wdestar said:


> ... So, for what it's worth - if you're young ... don't take your talents too seriously... and if you're older, it' not too late to retire.
> 
> Dan


So would a young guy and a older guy see the same spark? :jester:

This thread got my attention because of an article that I read in EC&M (Electrical Construction & Maintenance) magazine about sparking on the GEC when disconnected.

Without re-reading the article, I recall that it mentioned an open neutral as a possible cause. I went to my 240/120 3-wire panel at home, measured phase A with my Fluke clamp, measured phase B also. Measured the Neutral, and it didn't equal the difference between phases (it was more than the dif). I read current on the GEC. 
Hmm, WTF?? 
Could be brian john's residential reason? And/or does a neighbor have an open neutral, and their 'neutral' current is seeking its return to the source (either through the earth and/or water pipes) back up through my ground system, on my neutral up to the transformer?
Wierd.
My water pipe is my only grounding electrode. No ground rod.


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## waco (Dec 10, 2007)

brian john said:


> I have neither problem I know what I know and what I do not know I investigate to learn more about my profession.


Good. Now calculate the resistance of your skin versus the voltage in question.


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## RePhase277 (Feb 5, 2008)

Waco, I understand what you are saying. I have seen the same thing. I think that the main reason for it is the fact that some neutral current must flow through the earth from the GEC to the earth ground at the utility transformer. This is an inescapable consequence of the laws of physics. As long as the utility grounds their transformer, and then the electrician grounds his neutral, well, we are going to have some earth current. And this current may be enough to show a tiny visible spark when the path is opened.


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## gilbequick (Oct 6, 2007)

brian john said:


> Number one cause in a residence IS where several houses are off the same transformer and have copper water pipe for water supply. Then you have multiple neutral bonds and the water pipe (or gas) carry some current.


How do you fix that? How do you know which houses are fed off of which transformers?


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## brian john (Mar 11, 2007)

1. Perform a zero sequence reading at the panel, measure L1, L2 and neutral simultaneously.
2. Measure current on driven electrode.
3. Measure current utility water pipe.
4. Measure current on water pipe in residence.

What you are trying to do is determine if there is an issue, does it originate in the house or from a neighbors.

Best solution is have a plumber install a dielectric coupling OUTSIDE the residence as installing this in the residence at present is a NEC violation. Well installing the coupling is OK but you must install your clamp on the street side of the connection.

IMO a dielectric coupling in the house is better than a neutral sharing ground issue.

In all the inspections I have performed I have never measured current on the driven electrodes. Not saying it is not possible just have never seen this.


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## waco (Dec 10, 2007)

In my opinion, measuring current with a clamp-on meter gives you, at best, an estimation of current flow. The measurement certainly isn't up to the standards required for any sort of comparisons. In fact, AC amperage measurements, even by direct methods, are dicey.


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## brian john (Mar 11, 2007)

My primary job in investigating neutral/ground issues is power quality concerns, the measurements are relative to the problem at hand. A reading of 100 amps is never noticed unless there is an issue, a reading of 2 amps if it results in equipment hum is a major issue.

I had a building that had a net reading of 27 amps who knew how long this issue existed? But one day they rent a store front to a graphic arts place and their CRT monitors go crazy. The building owner want to know who to blame. I tried to explain this issue may have existed from day one or maybe happened last week.

We (6 men) spent two 12 hour Sundays resolving the issue. Now he could have bought flat screen monitors for less than the labor BUT the installation was an NEC violation that could result in other issues and We suggested the investigation repair be conducted.


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## waco (Dec 10, 2007)

interesting specialty. I admit, my association with electronics rapidly declined with the advent of integrated circuits, so I have no recent knowledge of how (or how well) modern devices incorporate power conditioning into their designs.

I do know that grounding was an issue in laboratory environments, mostly because "ground" is subject to so many variables and influences. In those days, we isolated sensitive installations from "ground" so they operated in controlled electrical environments. I don't know what practices are in use today.


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## brian john (Mar 11, 2007)

waco said:


> I don't know what practices are in use today.


 
All kinds of hoo doo voo doo, when basic PROPER installation procedures will resolve 99% of the issues.


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## heel600 (Oct 31, 2007)

brian john said:


> My primary job in investigating neutral/ground issues is power quality concerns, the measurements are relative to the problem at hand. A reading of 100 amps is never noticed unless there is an issue, a reading of 2 amps if it results in equipment hum is a major issue.
> 
> I had a building that had a net reading of 27 amps who knew how long this issue existed? But one day they rent a store front to a graphic arts place and their CRT monitors go crazy. The building owner want to know who to blame. I tried to explain this issue may have existed from day one or maybe happened last week.
> 
> We (6 men) spent two 12 hour Sundays resolving the issue. Now he could have bought flat screen monitors for less than the labor BUT the installation was an NEC violation that could result in other issues and We suggested the investigation repair be conducted.


What did you guys do that took 144 hours?


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## brian john (Mar 11, 2007)

12 story building 3 levels of parking.

Arrange for an outage.
isolate all feeder neutrals
megger each feeder neutral
isolate all branch circuits and megger each branch circuit neutral
trace each circuit with a shorted neutral
repair all issues

We located numerous panels with neutral termination bar bonded 
3 phase 3 wire circuits were the installer utilized 4 conductor cable tied neutral in at panel and taped neutral green in disconnect and landed it as a ground
Shorted MC cable connectors
2" 6/32 switch screws cutting into the neutral
and a few other issues.

Once found a 4000 amp busway with the neutral bus shorted to ground this was in the middle of a 26 story run of busway.


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## bigredc222 (Oct 23, 2007)

Brian
What tool or meter did you use the most tracking down those problems? 
Chris


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## brian john (Mar 11, 2007)

Number one tool is a megger.


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## 220/221 (Sep 25, 2007)

I saw a spark on a ground wire once.

I had just installed about a dozen circuits in a large computer/call center/order taking place for new work stations. The hots/neutrals had not yet been terminated let alone energized.

I told them to call someone who went to college to help[ me figure it out.

I didn't hear back from them.


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## shrekf (Sep 27, 2007)

are there is normal situation if the system is neutral earthing isn't. When
there is a load, it will return to neutral, and when the system of neutral earthing is open during that time, it will present arc isn't it... and it not effect the safety device to operate cause its out of its control.


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## shrekf (Sep 27, 2007)

Just for knowledge.. is there will bring different when RCCD & ELCB is install together in the same line? with volt & same sensitivy....


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## brian john (Mar 11, 2007)

A ground conductor is NOTHING but a 5th conductor in a 3-phase 4-wire system or the 4th conductor in a single phase system. This Equipment Ground Conductor (EGC) is a separate copper conductor and/or EMT rigid and other approved metallic wiring systems, in addition any all building metallic components that are connected. This use of interconnected metal in a commercial facility as part of the EGC is very hard to avoid with steel framing concrete construction, copper piping, sprinkler systems and metal duct. In a perfect world the EGC should not see current FLAT OUT; this conductor should have no voltage or current present at any point in the system. But as noted in larger distribution systems there are a small amounts of leakage current. Until they have 100% insulation this will always occur. 
So if the system is installed properly there is only one connection between the neutral and ground this is at the system bond at the main service or at a Separately Derived System (SDS). Installed and maintained properly there should be no measurable current (other than possible leakage current). If you can measure current at the neural to ground bond connection, this should be investigated. As part of electrical preventative maintenance (EPM) we lift the neutral ground bond and with the service switches opened we megger the neutral to ground connection.
Many people get confused with grounding. If you remember that ground is nothing more than an additional conductor that should only carry current in a fault, it should simplify grounding, there is nothing mystical about grounding keep it simple.
*How to determine if there is a neutral ground issue*
You can measure ground current at the neutral to ground bond.
or
Measure ground current by taking zero sequence measurements that is utilizing an amp clamp or flexible current transformer encompass the hot/energized conductors and the neutral. The current measurement should be zero. This has certain problems in a residential service as the neutral ground bond is below the point where you can take these measurements.


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