Off Topic, but maybe you all can help....electrician

Howie718

Morning all,

Are you guys aware of any sites like this one that focus on electricians and their trade? I am not looking to learn about electricity, but an informative site with a contractor look up would be valuable as I cannot seem to rectify what I perceive to be an issue.

I live in a section of Bergen County where utilities are underground and all of the houses are using the cold water pipe as the grounding electrode. I always have amperage on my ground line to the cold water pipe. Between 2 different electricians amperage recordings have been as low as .1amp and as high as 3.2amps. During their investigations it has fluctuated greatly. I have had PSEG at my house 2x to check my connections and both electricians checked everything on the house side of things. Everyone is scratching their heads saying "maybe" this is normal. But when PSEG acknowledged the imbalance and said they didn't know why....I feel there is an issue that I don't want to end in something serious.

Thanks, Howard

ChrisJ

Howie718 said:

Morning all,

Are you guys aware of any sites like this one that focus on electricians and their trade? I am not looking to learn about electricity, but an informative site with a contractor look up would be valuable as I cannot seem to rectify what I perceive to be an issue.

I live in a section of Bergen County where utilities are underground and all of the houses are using the cold water pipe as the grounding electrode. I always have amperage on my ground line to the cold water pipe. Between 2 different electricians amperage recordings have been as low as .1amp and as high as 3.2amps. During their investigations it has fluctuated greatly. I have had PSEG at my house 2x to check my connections and both electricians checked everything on the house side of things. Everyone is scratching their heads saying "maybe" this is normal. But when PSEG acknowledged the imbalance and said they didn't know why....I feel there is an issue that I don't want to end in something serious.

Thanks, Howard

You're going to get a lot of responses to this and I'd almost guarantee they're going to say it's not normal, can never be normal and must be fixed.

That said,
The house I grew up in NJ used the cold water pipe as the ground with no ground rods and I had measured considerable voltage on it and was told by our neighbor who at the time was an electrical engineer that this was typical and the reason they started using separate ground rods. He had said when many houses were all connected to the same pipe it would cause a voltage on the pipe vs actual ground.

I have no idea why it was that way but I can tell you it was that way for the 24 years I lived there and it was enough that if I tried to touch a wire from a ground rod to the water pipe it would give a decent spark. I also had issues with ground loops with audio equipment and had to isolate grounds etc.



I have none of these issues in my current house which uses it's own ground rod.

That's all I can tell you.

mattmia2

It is very likely a bad neutral but not in your service but in one of the neighbors. Their neutral current is flowing through the ground, through the water main, and to you and your neighbors' neutral connection to the utility.

STEVEusaPA

Yup, I'd lean toward a primary neutral breakdown, somewhere in the near neighborhood. PSEG won't find it or fix it, unless by luck, as it's pretty hard to nail down.
Bonding is usually more important than grounding.

This might be all the info you need...but you'll have to dig. If I can find the 2 videos I was thinking of, I'll edit my post.

https://www.youtube.com/c/MikeHoltNEC/videos

Edit: Here's one of the videos that pointed me to Mike Holt:
https://youtu.be/q-RrufV6Gig

Edit2: This may be helpful, or at the very least eye opening:
https://www.youtube.com/embed/wyOILpoR39A

archibald tuttle

I was in a house with a bad neutral. Often happens from leak on the line from the weatherhead into the meter box or sometimes even through to the breaker box. Ironically, this house was owned by a serious double E and he had neutral, to the extent he had i,t through his water pipe to neighbors house to their neutral .

But he had an electrician look at it when his load was fairly balanced across the 220 and under those circumstances the water pipe was sufficient to keep the voltage on both legs looking equal and an electrician told him, nothing to worry about. I told him otherwise but i wasn't an electrician.

Anyhow, you speak about amps and not volts found on ground and between what? 

It is not uncommon at times of high usage in neighborhood to see even 9 or 10 volts between neutral and ground and or between the ground pipe or rod and the ground itself which represents the line loss between the substation and your home which increases with amperage draw. (So you'll just see a few volts at low usage times).

That is showing potential and just being attached to a ground pipe or rod does not make that potential disappear. The ground is a lousy conductor but voltage trying to find its way back to the substation doesn't just take the path of least resistance, but takes all paths to ground proportional to resistance. So that includes through the water pipe to ground, to neighbor's neutral but also through you if you are grounded and grab the water pipe with this minor voltage on it.

I've noticed this effect most when wet grinding with a double insulated tool on a GFI circuit  because this voltage is outside the GFI control (that compares amp draw across the legs between the tool and the plug. that is unaffected by you providing a ground to the current on the bonded neutral upstream of the plug. So you can still get a pretty sharp zap, possibly enough to be dangerous nevermind bothersome  painful and disconcerting.

They chose the wrong transformer standard in the US and this is a big sleeping problem, while they are busy trying to get more and more of our economy on the grid  and they spend absurdly on the smart grid while not getting what we have got working well.

The electric forum i use that has serious discussion on various voltage on ground issues is mikeholt.com

They aren't too bad as those sites go  but partly because electricity can be immediately dangerous to people and partly because electricians (at least those who dain to participate) seem to me to be more prissy than plumbers, there is a whole lot more barrier erected as to homeowners figuring out their own stuff. 

Jamie Hall

One minor thing to remember in all this -- sort of hinted at above -- if the load on the two hot phases is unbalanced -- in any of the structures connected to a specific transformer -- the neutral will be carrying current -- really unbalanced, it can be carrying a lot of current. That will give you a voltage drop between the transformer and where the neutral comes into your house. Now if you measure between the neutral, if it not well grounded at the house or whatever, and a good ground, voila -- you will be measuring that voltage drop. A water pipe is usually a pretty poor ground -- and not all that many houses, particularly older ones, have a really good ground.

EBEBRATT-Ed

This is a common issue. Corroded or loose neutral is the first thing to look at.

The best test is to shut off your main circuit breaker and see if the amps on the water pipe drops.

The current reading on your water pipe may be from a neighbor's house. The video posted is from a 'sub panel" which is a different issue.

I copied the following from a post on Mike Holt's forum which explains it better than I can.


"As far as current on the metal underground water piping grounding electrode connection. This is 100% normal as the metal underground water piping is a physical parallel path for neutral current. Each service in the area is bonded to that common underground metal water piping system and this parallel path is a current divider. It is not uncommon for 20% or more of the neutral current to flow on the water piping system.
There will often be current on the water pipe grounding electrode even where the service to that building is turned off at the service disconnect that there is still a parallel path for the neutral current from the other services in the area via the water piping system, the grounding electrode conductors and the main bonding jumpers.
This path is a source of EMF, and about the only way to eliminate it is to discontinue using the metal underground water pipe as a grounding electrode. To do so would result in a code violation as you are required to use the metal underground water piping system as a grounding electrode if is present. You can minimize the current flow by installing a section of non-metallic water piping underground to break the physical connection to the rest of the metal underground water piping system in the area."


Note: if you take out a section of metal pipe and install plastic you need to leave a minimum of 10' of metal pipe to use as a grounding electrode

Howie718

Thank you everyone. I will check out Mike Holt's site and see where this takes me. By no means am I looking to figure this out myself.....I am really trying to find someone qualified to do so.....seems like it takes a village these days

Regards, Howard

ChrisJ

EBEBRATT-Ed said:

This is a common issue. Corroded or loose neutral is the first thing to look at.

The best test is to shut off your main circuit breaker and see if the amps on the water pipe drops.

The current reading on your water pipe may be from a neighbor's house. The video posted is from a 'sub panel" which is a different issue.

I copied the following from a post on Mike Holt's forum which explains it better than I can.


"As far as current on the metal underground water piping grounding electrode connection. This is 100% normal as the metal underground water piping is a physical parallel path for neutral current. Each service in the area is bonded to that common underground metal water piping system and this parallel path is a current divider. It is not uncommon for 20% or more of the neutral current to flow on the water piping system.
There will often be current on the water pipe grounding electrode even where the service to that building is turned off at the service disconnect that there is still a parallel path for the neutral current from the other services in the area via the water piping system, the grounding electrode conductors and the main bonding jumpers.
This path is a source of EMF, and about the only way to eliminate it is to discontinue using the metal underground water pipe as a grounding electrode. To do so would result in a code violation as you are required to use the metal underground water piping system as a grounding electrode if is present. You can minimize the current flow by installing a section of non-metallic water piping underground to break the physical connection to the rest of the metal underground water piping system in the area."


Note: if you take out a section of metal pipe and install plastic you need to leave a minimum of 10' of metal pipe to use as a grounding electrode

So,
My old neighbor was correct?

BTW, why do you have to use 10' of metal pipe as a grounding electrode? Wouldn't it be better to install two grounding rods and just bond the remaining pipe if any to the system?

JUGHNE

The high voltage utility primary often utilizes a "common" neutral for it's 7200 volt system.

Bad connections on the primary neutral will make the grounded wires conduct the current back to the sub-station thru the "earth ground".

I have dealt with this in the country producing stray voltage, with the problem being possibly miles away.

In the city it could be within a few blocks.

May be located by putting a digital voltmeter across each neutral connection.
If any voltage shows then that connection is not 100%.

ChrisJ

JUGHNE said:

The high voltage utility primary often utilizes a "common" neutral for it's 7200 volt system. Bad connections on the primary neutral will make the grounded wires conduct the current back to the sub-station thru the "earth ground". I have dealt with this in the country producing stray voltage, with the problem being possibly miles away. In the city it could be within a few blocks. May be located by putting a digital voltmeter across each neutral connection. If any voltage shows then that connection is not 100%.

What does that mean?
If any voltage shows?

1.0 volts?
0.1?
0.001?
0.0001?

I highly doubt you'll ever see absolutely no voltage drop.

mattmia2

If you see something you can measure over the inch or 2 of metal that comprises the connection then that connection has high resistance or isn't connected at all.

JUGHNE

The connection should have the same resistance as a short length of the conductor.

Some wirenut connectors boost of less resistance than the conductor itself.

Of that I am a little leery.

However testing across a good closed compressor contactor you may see no voltage at all.
So a good compressed connector should show no voltage at all.

I have done it with only 240 volts and see no voltage drop on a good connection.

ChrisJ

I was picturing measuring each neutral at a box.

I've never seen zero assuming there's any load on the neutral.

But you're talking often 25-50 feet of wire.  When we first bought our house I ended up metering each outlet and checking for voltage drop 

mattmia2

JUGHNE said:

Some wirenut connectors boost of less resistance than the conductor itself.

Technically it is true but meaningless. The conductor is doubled up or more so the area is double or more so it is lower resistance than the wires emerging from it...

EBEBRATT-Ed

@ChrisJ

In the old days most every building had a metal underground water pipe...even if they had a well. So that's where the EGC was attached. You can also use underground metal well casing.

Then the advent of plastic pipe. So the code decided to drive 1 ground rod and also use the metal underground water pipe "if available".

It is still that way.

As far as the # of ground rods you can drive 1 and use it........If you test it and it is below (25ohns I think). Since most don't have the equipment to do the test the code says to drive two rods a minimum of 6' apart.

The best ground is 20' of #4 copper placed in the bottom of the buildings footing before the concrete is poured

archibald tuttle

@JUGHNE echos my novel. NEV (neutral to earth voltage) is quite common despite 'bonding', i.e. the building service ground being connected to the neutral. You can have problem with your own neutral but there can be other problems (including btw utility's undersized carriers for high voltage relative to increasing spot loads because the transformers in use throughout the united states don't isolate that line loss phenomenon from the end user). This is all thanks not only to the 50s idea of the electric home, but the suddenly popular fiction that the electric home is the cure for carbon). Can also show up from nearby neighbors poor neutral main connections if earth grounds are to metal piping common to both homes.

and these phenomenon invoke the response to @ChrisJ asking about what the voltage is as a general question and always finding some voltage between neutral and ground and thus between bonded pipe or ground rod and ground.

Haven't seen you post what the voltage is that is driving this amperage which can be tested from the ground wire at the pipe to the ground because the potential exists at that point even with everything connected. And you can also test the extent of the problem by amps if you shut off all circuits but a single 120V circuit that you can apply a signifcant load to, e.g. a hair dryer or halogen shop light or something. That would place the entire return on the neutral because there is no balancing load in the house. Then test the amp load on the hot side of the circuit and on the neutral line to the meter, i.e. toward the utility from the bond. These tests can be made with a non contact clamp style ammeter keeping you better isolated from the wires and should reveal similar amperage. Any significant difference indicates an occluded neutral connection in your service or via common metal piping from nearby home. Small difference is usually the probably @JUGHNE and I have mentioned which is the additive line and connection loss to resistance for the return of all current from your neighborhood although to read an amp flow difference that small you probably need much better ammeter than you will have quick access to which is why I use the surrogate of voltage to ground which, as i say, commonly varies and can be as high as 9 or 10 volts when there is heavy usage across the utility system (this is a big problem, btw, with livestock when you put trough heater in a water tank then the animal becomes the ground for that voltage and it causes them not to drink. we have to eliminate the grounds on our heaters and run them on GFIs to combat this problem.)

There is further you can go to determine whether the problem is to your service or outside the home somewhere acutely or really a system capacity problem that is irremediable. But these often require access to meter box and contact experiments that you need to know what you are doing (not that that is something the average person shouldn't be able to learn safely and easily but if you don't have a grounded (:-) sorry) knowledge you would want to study more extensively or bring in help.)

Jamie Hall

The whole thing is interesting -- if only in an academic sort of way. Of course, at one time the theory -- and practice -- was that one had all metal piping (copper or steel or iron) to all the plumbing, and the neutral and the piping was bonded -- so even if at your location there was a difference in voltage between your piping and a true ground (such as @EBEBRATT-Ed suggested up there) it wasn't a big deal. You wouldn't get a tingle when you touched a faucet. And if you had a gas line or an oil pipe, that was all bonded too.

But... not so much any more!

archibald tuttle

@Jamie Hall rightish, although the reason for GFCIs near plumbed fixtures is that this bonding is a possible ground for any current that is loose. The irony is that this bonding also means that the low potential neutral to earth voltage potential may be on the faucet, so whereas principle GFCI concern, you touching loose hot current and the sink providing a ground can be reversed although that is mostly present in basements or slab on grade where you might touch the sink faucet while your self standing in bare feet on an earth ground. i can tell you that putting a knee down onto a wet floor while holding a grounded tool worked just fine when my rubber soled shoes had been protecting me. And this phenomenon is really tough on hooved animals who are really well earth grounded and drink out of water troughs with heaters with a connection to the system ground.

@EBEBRATT-Ed, see we use the same electric forum. I hadn't read that post with 20% on ground piping figure, but that really doubles down on the problems of Neutral to Earth voltage because this is all still a matter of the resistance on this current return including both the intended wire and any bonded grounding. Indeed, depending on the continuity of the piping system, that itself can be high resistance path at points. The voltage between the bonding ground and the earth in your basement represents the line loss of that entire system.

This is a good fusilade against the current US distribution system, but the basic down side of knowing this is that the fix requires installing an additional conductor on virtually every pole in america. (although i have also read that a good deal of it could be managed by installing new transformers that better isolate the phenomenon, still a very big and expensive fix). Haven't read the whole thing and I'm going to refrain from endorsing the perspective that the problem is cheapskate utilities in the sense that, utilities are us. we pay the costs of what they do and in theory them saving money is us saving money. at the margins they may convince regulators some expenses are necessary, but they usually prefer expenses that provide them with enhanced recovery (e.g. our local utility was forced to buy absurdly expensive wind energy avearge 35 cents/kwh over the life of the project which they are assured to collect from their rate payers but they got 2.5% of the deal to make them stop objecting!) This happens both public and private utility operators because public systems tend to treat their institutional interests not particularly differently than the private side utilities treat their stockholders. So, despite the difficulties posed to farmers and possible dangers to people as well, I'm not sure we can make the case that we should now engage in the hundred year project of righting this potential wrong, although it is as seriously demanding of consideration as any 'smart' grid. While in theory this is a sleeping disaster and danger, it has not resulted in traceable harms to people I'm aware of and it may indeed be that cost benefit cuts against an expensive fix (which is going on your electric bill if it happens).

The other thing that is demanding of consideration is, as we improve energy storage technologies, it is quite conceivable that we should effectively be reversing the rural electrification act and getting people off the grid (surely to have some solar wind and storage but also buttressed by, you know, fossil fuels as a back up (say a bidirectional plug-in hybrid).

as far afield as i can go at the moment.

JUGHNE

I recall reading in EC&M, electrical magazine, an article under their "Forensic Investigations".

This situation was a minor house fire caused by an overheated bonding wire.
It could have been a much worse disaster.

The utility lost it's neutral connection back to the sub station.

With the common shared neutral/ground system the current from the primary (7200 volts) was returning thru the customer neutrals looking for a ground path.

The house with the fire seemed to get the most current flow thru it's neutral and then on to the water pipe.
The bonding bare copper #6 flowed enough amps to get hot enough to ignite the drillings left on the top of the basement sill plate.

Now #6 bare copper will easily pass 100 amps in free air so there were considerable amps moving.

So this is a reason to not remove the water meter bonding jumper and to clean up drill shavings left around.

That periodical had several good articles, but the Forensic articles were the most interesting.

Reports of the unusual happenings that cost lives and property.
Many situations one never thought possible.

IIRC, the metallic water line, especially connected to a conductive main with numerous taps, is the best grounding system.
The UFER system is next and was developed by none other than Mr. Ufer as an answer to non-metallic water piping. Rebar in the footing with the weight of the building on it is important, IIUC.
Then 2 ground rods.
Then the structural iron of buildings.

We use all when they are available.

ChrisJ

JUGHNE said:

I recall reading in EC&M, electrical magazine, an article under their "Forensic Investigations". This situation was a minor house fire caused by an overheated bonding wire. It could have been a much worse disaster. The utility lost it's neutral connection back to the sub station. With the common shared neutral/ground system the current from the primary (7200 volts) was returning thru the customer neutrals looking for a ground path. The house with the fire seemed to get the most current flow thru it's neutral and then on to the water pipe. The bonding bare copper #6 flowed enough amps to get hot enough to ignite the drillings left on the top of the basement sill plate. Now #6 bare copper will easily pass 100 amps in free air so there were considerable amps moving. So this is a reason to not remove the water meter bonding jumper and to clean up drill shavings left around. That periodical had several good articles, but the Forensic articles were the most interesting. Reports of the unusual happenings that cost lives and property. Many situations one never thought possible. IIRC, the metallic water line, especially connected to a conductive main with numerous taps, is the best grounding system. The UFER system is next and was developed by none other than Mr. Ufer as an answer to non-metallic water piping. Rebar in the footing with the weight of the building on it is important, IIUC. Then 2 ground rods. Then the structural iron of buildings. We use all when they are available.

So.

I should run 0000 gauge to 2 ground rods for my 100a service?

Or use a 3 phase panel with the third phase handling the neutral so if it gets overloaded it'll trip the main?

archibald tuttle

@ChrisJ that's actually a clever idea re three phase panel. with all the use of alternative sources, i like three phase panels anyway to isolate the neutral. So there are approaches at the home level to try to cut yourself off from the worst of system issues that have caused documented problems like this.

i'm a little hazy on what would happen if we just made all our loads into 220 , e.g. started putting european stuff. then the house neutral would be superfluous but not the 7 grand neutral/return which is also earth bonded everywhere they can. I'm thinking, in theory, high resistance on the high voltage return would have less interest in our in house equipment grounding if it was not another pathway to neutral but there would be even more charged objects on the ground. all of this seems to me to recommend that additional unbonded return and the existing return becomes more like an equipment ground to manage faults, not to manage system load and serve to divert faults.

ChrisJ

archibald tuttle said:

@ChrisJ that's actually a clever idea re three phase panel. with all the use of alternative sources, i like three phase panels anyway to isolate the neutral. So there are approaches at the home level to try to cut yourself off from the worst of system issues that have caused documented problems like this.

i'm a little hazy on what would happen if we just made all our loads into 220 , e.g. started putting european stuff. then the house neutral would be superfluous but not the 7 grand neutral/return which is also earth bonded everywhere they can. I'm thinking, in theory, high resistance on the high voltage return would have less interest in our in house equipment grounding if it was not another pathway to neutral but there would be even more charged objects on the ground. all of this seems to me to recommend that additional unbonded return and the existing return becomes more like an equipment ground to manage faults, not to manage system load and serve to divert faults.

It's an interesting idea, but I'm betting no one would ever allow it.
Inspectors etc generally do not like oddball setups no matter how safe.

I've often wondered why we're bonded to ground in the first place. Doesn't that create safety issues in it self?

mattmia2

The bonding of the neutral to ground is to prevent the primary voltage from appearing on the secondary if the primary and secondary short.

ChrisJ

mattmia2 said:

The bonding of the neutral to ground is to prevent the primary voltage from appearing on the secondary if the primary and secondary short.

Why does dirt have anything to do with that?

If the entire system was floating, wouldn't it actually result in not being able to be shocked just because you're standing on concrete etc?

mattmia2

Without being referenced to ground somewhere static charge would be an issue and the amount of static charge that could collect on a system that large until it found a path to ground would be.....significant.

archibald tuttle

@mattmia2 that is my understanding. but to answer @ChrisJ question, the purpose of the bond is that enough current would travel to earth to trip the breaker. that is why the earth ground form the panel sizing is at or near the capacity of the main and ditto the circuit grounds returning to the bonded panel.

while this is a long sleeping problem, it has not, to my knowledge, actually lead to human casualties; although it is theorized that it must have somewhere but is unknown to have been the culprit. still, with the ubiquity of this system and having no body count, a lot of this argument is theoretical. speaking of which, in theory, if not in code, you could use fault interrupters on your service mains rather than bonding to accomplish the desired aim but we're talking massive nuisance problems and another maintenance headache.

in a microcosm, that is how I deal with a few individual circuits where the relatively low potential between neutral and earth (aka Neutral to Earth Voltage or NEV) during non-faulted operation, as opposed to more significant voltage crossed to the neutral or significant resistance on neutral causing that potential to increase noticeably beyond single digits, e.g. electric heated stock watering tanks, some milking machines, etc. where effectively grounded animals are exposed via grounded electric appliance to this potential. (the industrial agricultural solutions which are drastically expensive included embedding lots of rod in the ground or concrete around tanks and in milking parlours and that is also bonded raising the surface the animals are standing on to the same potential as the bonded ground . . . That seems to me like one backwards way of dealing with this, handing a problem created by the utility to the farmer; although maybe it is the comeuppance for the rural electrification act that created the relatively absurd premise that rural customers should be served on the same cost basis as urban customers despite the obvious higher cost per dwelling of infrastructure and its maintenance (not to mention increased distances to substations that raise return line loss even in the absence of significantly failed neutral splices).

And speaking of unintended consequences, increased rural use by exurban dwellers is responsible for strains on these systems where sprawl is encouraged by providing inappropriately low utility costs. What should happen in rural areas is prices should rise to reflect costs of service (including fixing stuff like this) and folks would be encouraged to get off the grid, especially if any of this pie in the sky renewable and storage tech actually meets milestones for improvement it will more practically enable off the grid operation or micro grids than readily be instituted at grid scale. That is one of the great ironies of those pressing for these technologies to enable the grid of the future. The grid of the future is no grid!

archibald tuttle

@ChrisJ "If the entire system was floating, wouldn't it actually result in not being able to be shocked just because you're standing on concrete etc? "

no, because the ground is where potential is effectively measured from, whether it is bonded to neutral or not. the bonding just associates the problems of potential on the neutral with the earth ground that exists to divert faults.

Jamie Hall

Since @archibald tuttle mentions stock tanks and milking machines and the like... it is a potential problem and, as he notes, livestock is far more sensitive to stray voltage than we are (it's why a flimsy electric fence will control a 2,000 pound druaght horse with ease!). Our solution -- and it was code, once upon a time, but I'm not sure it is now -- is that since we have a nice 40 foot steel well casing, full of water and firmly cemented into the surrounding rock, the neutral and the barn grounds are bonded at the barn switchboard and in turn connected to that well casing. There is no ground wire in the feed to the barn switchboard from the main house switchboard -- just the neutral and two hots -- and the house switchboard is bonded and grounded there.

It works.

ChrisJ

@archibald tuttle @mattmia2 @Jamie Hall

I guess I'm slow, but I am trying to understand.

So if I had 3 phase coming direct from a generator (maybe some step up and step down transformers along the way), which isn't grounded, and no where along the path is anything grounded, and that went to a transformer and stepped down to 240V and came into a house with two hots and a neutral(center tap) , again, nothing grounded.

I'd still see a difference between everything there, and earth? In my head I'd measure nothing, because nothing is connected to earth so it's not part of the circuit.

Jamie Hall

If you used a high impedance multimeter, you'd still see a voltage, @ChrisJ -- completely natural. "Static" electricity. Might not be much -- might be quite a bit. Same as if you have a disconnected wire -- it will often show a voltage relative to other wires or to ground (and can confuse the heck out of you).

JDHW

archibald tuttle@

I would be careful what you wish for adopting European electrical standards, some of the practice might be better but not all. UK Practice is described below.

On the distribution side all of the transformers feeding customers are connected between phases on the high voltage side and the system is earthed at the HV source. This earthing (grounding) is through an impedance (resistor, inductor or a high impedance earthing transformer) to limit the earth fault current. Distribution circuits are three phases and maybe an earth. In urban areas the distribution is via underground cables with and earthed outer, in rural areas it is normally wooden poles with the three phases on them and no earths. With this arrangement it is possible to make the protection much more sensitive to earth (ground) faults than over-current faults and this is a good thing.

On the low voltage supplies to customers there are three ways of doing things and this depend on the age of the installation and the environment.

In pre 1960's urban areas the supply is known as TN-S (Terra - french for earth) connected to neutral at the source transformer and then separate lives, neutral and earth to the customer. At the premises any incoming metallic services such as gas and water are cross bonded to the incoming earth connection but there is no requirement to have a local earth (ground rod). On these systems you will get a few volts difference between the earth and neutral conductors because of unbalanced currents flowing in the neutral. In this era supply cables were paper insulated oil with a lead outer sheath. A three phase cable with neutral runs down the street and individual houses get typically a single phase 100A supply at 230 Volts. Bigger premises get three phases. The two problems with this system are what happens if the cable sheath corrodes away - how can you tell? and if you lose the neutral connection to the transformer the phase/neutral voltages go all over the place - usually blowing up 2/3 of the customers equipment with over voltage.

More recent urban install installations the supply is known as TN-C-S. Earth (ground) connection at the transformer, three lives and a combined earth (ground)/neutral conductor on the cables in the street, at each customer an "earth" terminal is connected to the neutral and all internal wiring maintains the separate neutral and earth. At the premises all the incoming services are cross bonded to the earth (neutral) with bigger cables than TN-S but there is no requirement to have a local earth (ground). To make the system a bit safer in the case of a failed neutral connection at the source transformer the supply cable in the ground is periodically connected to earth (ground) electrodes by the utility company. This system is also know and PME - protective multiple earth.The system is self monitoring in a way in that the earth (ground) and neutral are the same so a failing cable will cause voltage problems and be obvious/corrected. I think this is the same as the USA practice and can/will cause earth/ground currents. A fault on the transformer neutral will cause the phase voltages to change. A big fault on the external cable could cause a big voltage rise on the combined neutral/earth (ground conductor) until the protection devices disconnect the supply.

The last supply form is known as TT. The neutral of the supply transformer is earthed (grounded) and there must be an earth (ground) electrode at every customer's premises and all services bonded together. The supply cable only provides live(s) and neutral. Because there is no metallic path for the earth (ground) faults back to the supply transformer the installation must have RCD (GFI) protection for everything. This form of supply is common in rural areas with bare overhead supply cables and is mandatory for high risk areas such as farms, petrol (gas) stations, marinas and caravan (trailer) parks.

The general trend is towards TN-C-S with rural systems being updated with bundled insulated conductors which provide an earth.

Then electric cars came along and everyone wants to charge them outside their house. Your house is connected to a TN-C-S system and there is snow on the ground, you go out the car and touch to door handle just as there is a big fault on the system - you car is now at 2-300 volts above the snow you are standing in! Rules now say if you have an external car charging point it must have it's own earth terminal and be wired as a TT system.

I think a big difference between USA and UK is that there are never any poles supporting both HV and LV cables. There are quite strict rules on the separation of HV and LV earths at transformers. Utilities must determine the maximum earth/ground voltage rise that could occur during an HV fault. The LV earth/ground system must far enough away from the HV to prevent hazardous voltages and the LV side. Have a look at https://www.cablejoints.co.uk/upload/Earthing___Guidance_Notes__Central_Networks.pdf for more detail.

John

Jamie Hall

Wonderful -- and useful -- explanation, @JDHW ! Thank you! The system -- at least in our immediate area -- is very like your "TT" system, and works very well indeed. We don't have GFCIs on everything, though (most of it was installed in the mid 1950s!). Be nice, but many thousands to upgrade.

I think one of the things that many people don't realise is that "earth" or "ground" potential is not even close to the same everywhere. While the current density may be very low (after all, dirt really isn't a very good conductor) that doesn't mean that the voltages are necessarily low. A local ground connection -- and a good one -- is needed to reference the "neutral" line to the local ground -- or, perhaps seen more accurately, to reference the local ground to the neutral. Since there is no neutral on the grid lines (we have three phases on the local grid supply), while the phase to phase voltages will be what they nominally should be, the phase to earth voltages are actually not constrained. Hence if your building drop comes from a centre tapped transformer, with that centre tap being the neutral, unless there is an earth connection at the building again the phase to phase or phase to neutral voltages will be what they should be, they are not constrained relative to earth -- unless there is a local earth.

Clearly if the three phase high voltage lines are fed by -- or connected to -- a Y connected transformer with an earthed neutral, the high voltage lines will be constrained -- at that location.

EBEBRATT-Ed

Transformers have ground rods driven at the pole for an overhead service and at the pad for pad mounted transformers. Thes connections and the neutral connection can degrade over time as well at the water pipe and driven rod connections at the house. The POCO doesn't provide a neutral it is created at the transformer.

I have seen houses with their power shut off and the stray current remains coming back through the ground/neutral from a neighbor's house.


So yes your neighbor could burn down your house

archibald tuttle

@ChrisJ I think you are right in a theoretical abstract. I think I overstated the point in opposition because we commonly talk about the reference for voltage measurement as earth but as i bend my mind around this, a fully isolated circuit wouldn't have potential to earth but to it's own reference. so you could grab it and you have the same potential but no current until you get a 'return', i.e. a second point of contact to the circuit.

In the real world, if we are just experimenting in a world without bonding, the use of earth to ground faults on both the primary and secondary means you almost will never encounter such an ideal circumstance. and are always at risk.

in a sense though, you are really suggesting that we potentially treat single phase as if it were two phases to better isolate it. in three phase you can link two of the coated phases for voltage and not bond either and then have separate grounding conductor for faults and we could treat single phase that way by insulating the return instead of bonding, at which point it would have made as much sense just to run two phases of the three phase because you get higher voltage and thus less line loss.

going back to the paper i linked though, here is the connection that sloughs some portion of any problem on the primary onto the secondary:



so i'm going to retract the contention this requires another insulated wire everywhere. the approach the author favors is phasing in another coated wire in single phase primary service (he doesn't actually propose that the other wire could make it effectively a two phase service because you wouldn't have to change the transformers, just remove the jumper (indeed the jumper, according to survey of engineers he cites is anathema to theoretical ideal transformer undertaking). They already have their fault grounds in place and they simply would no longer serve as a bonded path for the return and since the return would be a new insulated wire with new connections, eventually it could manifest connection problems, same as the hot side. And this would all take place over years just as the addition of equipment grounding outlets so the two systems would coexist for some time and as neighborhoods were completed they could go on to the new system. This is independent of house, i.e. secondary, neutral and bonding which would become completely separate from the primary.

actually makes sense to me (good reason for everyone else to double check the logic :-)

Jamie Hall

Yes, most pole transformers do have a connection from the centre tap of the secondary to ground. Not a very big one. Not always a very good one -- but it's there. However, in @archibald tuttle 's diagram, there is not a connection from the "neutral" of the primary to ground or the centre tap -- because none of the three hots in a three phase primary line is either neutral or earthed. We're being a little sloppy withh terminology here -- a three phase system has three hots -- let's say, for the sake of laughs, each is 23 kilovolts referenced phase to phase. The currents or voltages in each phase referenced to a common neutral (let's say a Y connection) are exactly 120 degrees relative to each other. However, in a normal single phase building drop, we have two hots, each 120 volts (in the US) to the neutral, but 180 degrees apart relative to each other -- and either exactly in phase, or 180 degrees out, relative to the hot pair tapped by the drop's transformer, if the drop transformer is connected phase to phase, or either in the case of a drop transformer connected from one phase to neutral (if there is one), in phase with that phase.

There really aren't two phases in most building drops -- just one, which happens to also have a centre neutral.

Now this has some interesting side effects. If the two "phases" from the building to the transformer are carrying substantially different loads, there will be a substantial current flowing in the neutral, and there will, consequently, be a voltage difference (which may be substantial) between the neutral measured at the building and the neutral/earth measured at the transformer (how long are the leads on your multimeter?!). Earthing the neutral at the building -- as well as at the transformer -- simply references the earth potential at the building to whatever the neutral potential is at that location, which is quite desirable. However, careful measurement will show that there is some current flowing in the earth connection.

Where this gets more interesting is let's suppose that you have a heavy load on one phase out in the building somewhere. There will then be a voltage drop in the neutral for that circuit. If, at that location, you also have a wired ground/earth connection (you should) you will discover that there is a potential difference -- again possibly substantial -- between the neutral and the ground at that location, since the "grounding" wire is not supposed to be carrying any current.

One can spend a lot of time trying to unconfuse one's self on this sort of thing! Or trying to get rid of ground loop hum in a sound system...

archibald tuttle

@Jamie Hall agree pretty much all, but that is a single phase diagram  this problem is more acute for the reasons you spe cify with rural/exurban single phase tangents. Our road is a mile and a half with 30 or 35 seevices like the one diagramed. The exacerbation in those cases comes from the utilityusingour grounds as additionaldrain for any voltage on rhe pri.ary return  rhat is the red circle that i added to the diagram which came from the linkedpaper.

Itis absoluety true that the problem could be fixed by running a swcond phase down our road instead of an insulated neutral but then the transformers would all need to be changed because the existing are for half the phase to phase voltage .

Jamie Hall

Further observation in our area -- most of the building drop transformers are off of one phase only, with the other side of the primary grounded (after a fashion) (not even tied back to a wired neutral). Old bit of grid. Voltage, even now, tends to be erratic. There are a few Y connected transformers a few miles away -- three phase services -- but still no wired neutral. I hate to think what it's going to be like in the new all electric world...

JUGHNE

Our first distribution system of 1920 was 3 hot phases directly out of the alternators (2400 volts) thru switchgear and out on poles.

2400 between the hots, 2 phases feeding transformers.
Nothing grounded anywhere.
Only ground rods for a few lighting arrestors.

Many services had 120 volt only. Typically 2 circuits. Each with open knife double switch and plug fuses for each leg. IDK the voltage to ground, both wires considered "hot".
Fuses would probably only open with overload on the circuit.
A lot of 30 amp plug fuses on 14 gauge K&T....with an occasional penny added.

Next upgrade in 1958, with the same primary of 3 phase Delta. No primary neutral/ground.
But transformers were all center tapped, bonded to the tank and ground rod at pole.
And then the neutral was grounded at least at the pole.
Grounding at the house thru ground rods or water lines was hit and miss.

And of course we have 3 phase banks with one transformer being center tapped for 120 loads, giving that elusive "wild leg"........confusing to some people.

Today most have new services with all the NEC bonding etc.

We are rebuilding the distribution system today after 62 years.
(pretty good life for the poles and cross arms, new will not last as long.)

Insulating for 7200 Volts. Eventually probably upgrade to 4160 Wye.
With 4160 (4 wire) you get 2400 between one phase and the neutral.
Allows you to reuse existing transformers, which are is short supply BTW.
Common neutral/ground run everywhere.
Going to 7200 will require changing all transformers.

IIRC, doubling voltage will produce 4 times the energy available, also less current draw on conductors for the same load will induce less line loss......the main purpose of this upgrade.

ChrisJ

Jamie Hall said:

Further observation in our area -- most of the building drop transformers are off of one phase only, with the other side of the primary grounded (after a fashion) (not even tied back to a wired neutral). Old bit of grid. Voltage, even now, tends to be erratic. There are a few Y connected transformers a few miles away -- three phase services -- but still no wired neutral. I hate to think what it's going to be like in the new all electric world...

All of the power in my parent's area of PA is like that.

A grounded wire travels along the top of the poles, and below it a single insulated line feeds all of the pole pigs on the road.

Jamie Hall

@JUGHNE -- do you have any idea how lucky you are to be a local electric utility?