Grounding conductor connected to grounded conductor

[Electrij]

TL;DR Summary

Question summarized:

If current always seeks the path of least resistance to ground, why does the neutral conductor not carry current directly to earth ground from the load?

Hello,

I’ve been working with electricity for a few years and have a misconception that was recently revealed again to me. I remember asking my teacher this question in school and him not being able to answer.

In North American homes (and other buildings), the neutral or “grounded conductor” is connected to Earth ground through the water pipe or a metal ground rod driven into the dirt. This is commonly referred to as bonding, where the grounded conductor (neutral) is bonded to the grounding conductor (ground) at point of service/first disconnect.

I’m trying to understand why current does not flow into the Earth from the load side of the load (neutral) if current always seeks the path of least resistance to ground. I have a hard time imagining that the path of least resistance would be through the dozens of distribution transformers and millions of feet of wire going back to the substation and power source, and not the pipe standing right next to you at the panel.

So perhaps I’m misunderstanding something in how power distribution works. I know that the neutral is “intended“ to carry current back to the source, and yes I know it is “meant” to balance out the three voltages of the power lines. I’m asking, “why” doesn’t the current just flow through the ground/neutral bond into the earth?

Consider this: if I fail to bond the neutral wire at the panel, most things in a home will still practically function except (except the breakers won’t trip necessarily in the case of certain shorts). But if I connect one of those lines to a path of low resistance to Earth ground, why does the current not go to Earth ground instead of to the source? This seems to be what is essentially happening when you bond a neutral at the panel.

Thanks in advance for answering my questions and helping to clear up some confusion.

 

[Guineafowl]

Summary:: Question summarized:

If current always seeks the path of least resistance to ground, why does the neutral conductor not carry current directly to Earth ground from the load?

current always seeks the path of least resistance to ground.

Current doesn’t seek the path of least resistance to ground. This is a very common misconception, perhaps stemming from studies of lightning. Current flows and returns to and from the source. If multiple paths are available, it will split according to the resistance of each path. If ground is a path, current will flow down it as for any other conductor. But don’t think of ground as a universal electricity sink when considering circuits.

In the set-up you describe, there is a parallel path consisting of the neutral conductor, which is a very low resistance back to the transformer, and the ground path, which will be higher resistance. Current in this system will split between the two paths according to the parallel resistance rule: 1/Rtotal=1/R1+1/R2...etc.

A typical service cable to a UK house will be under 1 ohm in resistance, while the path from the Earth rod, through the ground and to the transformer is considered good if under 100 ohms.

 

[FactChecker]

CORRECTION: THE TERMINOLOGY HAS BEEN CORRECTED as @sandy stone points out in post #15. Thanks @sandy stone .
In the USA, "hot" refers to the AC source wire, usually color coded black. "Neutral" refers to the AC return wire, usually white, and "ground" refers to the safety wire connected to the metal frame of an appliance, usually green or uninsulated.

It's a safety thing. There should be no current on the ground safety wire. It is connected to the metal exteriors of light fixtures and appliances. The real working current is supposed to go back on the "neutral" wire. That allows ground fault plugs and switches to detect an imbalance between the currents on the hot and neutral wires and break the circuit. A danger in old wiring without a ground safety wire was that two appliances might get different wires (hot or neutral) touching the metal exterior. A person touching both appliances would get a bad shock. In a modern wiring circuit, if any hot wire touches the exterior of an appliance, that immediately allows a direct current path to the ground along the ground safety wire, and a ground fault device would detect a current imbalance on the hot and neutral wires and break the circuit. In fact, this is true if there is any significant current on the ground safety wire. And finally, the ground safety wire provides a very simple path to ground with no complicated paths to consider.

 

[Electrij]

Current doesn’t seek the path of least resistance to ground. This is a very common misconception, perhaps stemming from studies of lightning. Current flows and returns to and from the source. If multiple paths are available, it will split according to the resistance of each path. If ground is a path, current will flow down it as for any other conductor. But don’t think of ground as a universal electricity sink when considering circuits.

In the set-up you describe, there is a parallel path consisting of the neutral conductor, which is a very low resistance back to the transformer, and the ground path, which will be higher resistance. Current in this system will split between the two paths according to the parallel resistance rule: 1/Rtotal=1/R1+1/R2...etc.

A typical service cable to a UK house will be under 1 ohm in resistance, while the path from the Earth rod, through the ground and to the transformer is considered good if under 100 ohms.

can you explain to me why it is then that current will prefer to flow to ground if given the option?

Take for example a transformer with a high amperage breaker feeding several sub panels or feeders. At the point of customer use (say an outlet), if you touch the hot to a metal ground then it will go into the earth, even under load. It does this even if the particular metal ground isn’t bonded to the neutral back at panel.

I’ve actually troubleshot this on machines that do not have a properly bonded path back to the transformer, but the neutral path is just fine. If the hot (or even the neutral) shorts to ground During load at the point of use, according to what your saying the path of least resistance is to ignore the path to ground and take the neutral (or hot) back to the source.

But it never does this. In practicality, it ALWAYS goes to ground. People get killed or shocked, or equipment gets fried, because they provide a path to Earth ground in improperly bonded systems.

 

[Electrij]

now maybe the possibility exists that a high resistance ground path back to the source exists, and so, like you said, you have two parallel return circuits to the source.

but that should only apply to properly bonded and grounded transformers and systems. without the bond, then there really shouldn’t be any return path to the source at all.

And yet these types of improperly installed or faulty systems that don’t have an Earth ground are among the most dangerous to work on.

I was under the impression that was because the full load was going into the earth, not seeking a non-existent path back to the source.

 

[Guineafowl]

can you explain to me why it is then that current will prefer to flow to ground if given the option?

As I say, current will only flow to ground if it’s a path to/from the source. The ubiquity of earthing systems makes it seem like current ‘wants’ to flow to ground. Look up ‘isolation transformer’ for a demonstration - these clever devices remove this earth/ground reference and show how electricity behaves without the neutral/earth safety system that we impose on it.

Take for example a transformer with a high amperage breaker feeding several sub panels or feeders. At the point of customer use (say an outlet), if you touch the hot to a metal ground then it will go into the earth, even under load. It does this even if the particular metal ground isn’t bonded to the neutral back at panel.

Draw this system out for me, as there are so many systems around the world.

according to what your saying the path of least resistance is to ignore the path to ground and take the neutral (or hot) back to the source.

No - current does not ignore higher resistance paths and take the one of least resistance. It splits in proportion to the resistance of each path. In this case, the majority of current will flow along the neutral.

 

[Electrij]

As I say, current will only flow to ground if it’s a path to/from the source. The ubiquity of earthing systems makes it seem like current ‘wants’ to flow to ground. Look up ‘isolation transformer’ for a demonstration - these clever devices remove this earth/ground reference and show how electricity behaves without the neutral/earth safety system that we impose on it.Draw this system out for me, as there are so many systems around the world.No - current does not ignore higher resistance paths and take the one of least resistance. It splits in proportion to the resistance of each path. In this case, the majority of current will flow along the neutral.

so if I’m understanding what you’re saying properly...

if we never connected any of our power distributions systems to Earth ground, it wouldn’t travel through Earth back to source?

 

[Electrij]

So in other words, I can really only get shocked on an unbonded, ungrounded isolation transformer if I touch between neutral and hot? Not hot or neutral to Earth ground?

 

[Electrij]

(Not saying I would try it lol)

 

[FactChecker]

So in other words, I can really only get shocked on an unbonded, ungrounded isolation transformer if I touch between neutral and hot? Not hot or neutral to Earth ground?

CORRECTION: SORRY, I DIDN'T NOTICE THAT THE QUESTION WAS ABOUT AN UNGROUNDED ISOLATION TRANSFORMER.
No. Not true for neutral and definitely not true for the hot wire. There is practically always some potential difference between two widely separated ground points. Any ground you touch is probably a significant distance away from the electrical wiring ground and the Earth between the two points has a significant resistance.

FYI. In fact, one of the dangers of lightning is when a person is lying on top of a rubber cushion with feet and head (or hands) touching the ground. Near a lightning strike, the potential difference between his feet and his head can be great enough to cause serious injury.

 

[Electrij]

No. Not true for neutral and definitely not true for the hot wire. There is practically always some potential difference between two widely separated ground points. Any ground you touch is probably a significant distance away from the electrical wiring ground and the Earth between the two points has a significant resistance.

FYI. In fact, one of the dangers of lightning is when a person is lying on top of a rubber cushion with feet and head (or hands) touching the ground. Near a lightning strike, the potential difference between his feet and his head can be great enough to cause serious injury.

yes, but at some point the resistance is so high that it’s not really differentiated from the air gap between two conductors an inch apart.
So barring a conventional path through ground, e.g., if an isolation transformer (or a maybe something else like a gas generator) is mounted on a heavily insulated surface like a rubber mat, the point is that the hot wire will not conduct current to an Earth ground through something like a water pipe or perhaps the two bare feet of an idiot grabbing the hot with his tongue?

 

[Guineafowl]

So in other words, I can really only get shocked on an unbonded, ungrounded isolation transformer if I touch between neutral and hot? Not hot or neutral to Earth ground?

Exactly - in this case the earth/ground is not part of the circuit. Old TV techs would use an isolation transformer while working on live sets, trying only to use one hand.

And remember - the outputs of an isolation transformer are no longer hot or neutral, just two AC terminals.

 

[Guineafowl]

No. Not true for neutral and definitely not true for the hot wire. There is practically always some potential difference between two widely separated ground points. Any ground you touch is probably a significant distance away from the electrical wiring ground and the Earth between the two points has a significant resistance.

This doesn’t seem right - in an isolated supply, there is no hot or neutral, and ground doesn’t come into it. I’m talking about a bench isolation transformer powering some appliance. Perhaps you mean something different?

 

[FactChecker]

This doesn’t seem right - in an isolated supply, there is no hot or neutral, and ground doesn’t come into it. I’m talking about a bench isolation transformer powering some appliance. Perhaps you mean something different?

Yes. I saw your post and realized that I had missed the point. I have corrected that post. Thanks.

 

[sandy stone]

It's a safety thing. There should be no current on the neutral ground wire. It is connected to the metal exteriors of light fixtures and appliances. The real working current is supposed to go back on a hot wire. That allows ground fault plugs and switches to detect an imbalance between the currents on the two hot wires and break the circuit. A danger in old wiring without a neutral wire was that two appliances might get different wires touching the metal exterior. A person touching both appliances would get a bad shock. In a modern wiring circuit, if any hot wire touches the exterior of an appliance, that immediately allows a direct current path to the ground along the neutral wire and a ground fault device would detect a current imbalance on the two hot wires and break the circuit. And finally, the neutral wire provides a very simple path to ground with no complicated paths to consider.

I'm not sure where you are located, but for readers in the USA, the terms you are using might be dangerously confusing. In the USA, "hot" refers to the AC source wire, usually color coded black. "Neutral" refers to the AC return wire, usually white, and "ground" refers to the safety wire connected to the metal frame of an appliance, usually green or uninsulated. There is no "neutral ground wire", and "neutral", although it should be only slightly above ground potential, is never connected to the exterior of an appliance. There is only one "hot" wire.

Your explanations were very good, and I only point out the terminology conventions for safety.

 

[Electrij]

Holy f*ck my whole understanding of electricity has drastically changed!
It all makes sense, though.
so if someone could please confirm th summary of my understanding I would appreciate it.

electricity doesn’t seek the path of least resistance to ground. It seeks the path of least resistance to its potential difference, or source.

We use the Earth as a sort of backup conductor between potential differences (among other reasons) in case something goes wrong. The bonding or grounding conductor is used to help conduct any unwanted potential difference through metal or ground back to its source. It’s purpose is NOT necessarily to bring unwanted potential differences to ground, except for the fact that we are using the very dirt itself as a conductor back to source, hopefully through a nearby neutral bond.

Is this essentially correct? Am I missing anything crucial?

thanks for all your help guys.

 

[Guineafowl]

Forgive me if I’m repeating things already said, but I’m often asked this question and would like to craft a perfect answer.

We need to define polarity:
For DC, it refers to the direction of current, conventionally from pos to neg. We always bear in mind that the real electron flow is the other way.

For AC, the direction reverses at the supply frequency, so AC has a different definition of polarity: Live and neutral.

A raw single phase AC supply doesn’t have live or neutral, just two equivalent terminals. We ground/earth one terminal, and call that neutral. The other is live. Why?

1. So that the live conductor does not rise more than the supply voltage above ground/earth, which might lead to clearance/arcing issues and may degrade wire insulation.

2. So that there is a dedicated path (ground/earth wire) for fault currents to flow, thereby tripping the protection. This applies mainly to metal-cased appliances and armoured cable.

3. If we left the supply floating, inevitably one wire will get a ground/earth reference from a fault, but this will be a silent fault. All other users on that supply will be affected, but will not notice until a second fault occurs.

4. For polarised plugs, it ensures it’s always the live conductor that is broken by a switch or breaker, rendering the load relatively safe.

This confusion about earth/ground is very common. I wrote the above in an old thread. Hope it helps.

Two possible failures in electrical teaching:
1. The idea of current going ‘to’ ground. It doesn’t. It goes through ground and back to source, because of the safety system we use - earth/ground as a conductor. We’ve dealt with this.

2. Electricity takes the path of least resistance. Try to stop saying this, as it’s partially untrue, or at least misleading. Current flows through all available paths according to their respective resistances.

 

[davenn]

Is this essentially correct? Am I missing anything crucial?

no, yes you are

electricity doesn’t seek the path of least resistance to ground. It seeks the path of least resistance to its potential difference, or source.

It doesn't SEEK, period. It doesn't have a mind ... you seem to still not grasp that
Current will flow through ALL resistances, proportional (inversely?) to the resistance of that path

We use the Earth as a sort of backup conductor between potential differences (among other reasons) in case something goes wrong. The bonding or grounding conductor is used to help conduct any unwanted potential difference through metal or ground back to its source. It’s purpose is NOT necessarily to bring unwanted potential differences to ground, except for the fact that we are using the very dirt itself as a conductor back to source, hopefully through a nearby neutral bond.

The neutral like you have coming into your home is "generated/made" locally ... namely at a transformer pole
in your street / suburb . The neutral doesn't go all the way back to the power generation station.
The major power transmission lines from the generating station (source) don't include a neutral,
they are all phase's usually sets of 3 phase lines.

have a look at this site ...
https://www.powerandtest.com/-/media/ametekprogrammablepower/files/pdfs/ac power distribution.pdf?la=en

 

[artis]

In a balanced 3 phases system the current travels between phases, in any given instant it can travel forward in one phase and backwards in another of the 3 phases.
in your local transformer the current that goes to your house/es is not the same current that came from the power plant, it is galvanically isolated through the transformer.
so now you have a second lower voltage loop between your local transformer and the load attached to it.
for single phase in this loop the current will travel between the hot or phase wire and neutral wire.I assume you are within USA so you there have a code that says that all wires should be isolated from one another except at the breaker box the neutral can be tied together with the ground wire. So if any potential develops on a device surface within the house it should flow back to the neutral conductor.
Now I am not entirely sure as to why US implemented this system, one reason I could think is because it is important that the ground wire has a low resistance path otherwise it doesn't function well and cannot increase safety, so because not in all places one can have a good low resistance ground path (due to soil differences etc) the neutral is a failsafe.
Also I read that it was done in order so that the breakers would trip upon a fault (current differs between hot and ground) but in modern GFCI breakers they can do without the ground wire as they measure the current difference between hot and neutral and so if there is a difference even small it is clear that there is a fault so the breaker trips.

https://en.wikipedia.org/wiki/Electrical_wiring_in_North_Americabut in general as others have said, electric potential doesn't seek a single path, it will use any available path to anything of lower potential, in other words electricity only cares about resistances, so if you have a 120v hot wire that is attached to a light bulb to neutral and then you touch the hot wire yourself while standing on the ground, it will happily go through both the bulb to neutral as well as through you to ground. the amount of current in each load (you or bulb) will then be determined by the resistance.
So if you have a higher resistance than the bulb + the ground beneath you is very dry and also has a high resistance then more current will go through the bulb and less through you but in any way current will pass through both loads.

@Electrij I'm sure you know the old screwdrivers with a lamp inside that when you touch it lights up, what do you think , how do they operate ?

 

[Baluncore]

A fuse is used in a circuit to limit high current due to a short circuit, that would otherwise damage the conductors, switches, and set fire to the insulation.

A ground bond is used to protect the insulation from voltage breakdown. If the circuit was free to float to any voltage, the insulation could be punctured by a nearby lightning strike. That is also one of the reasons why a protective Earth PE is used for appliances that could present a shock hazard, or pick up an insulation damaging static voltage.

AC power is distributed through transmission lines. When the currents in the wires sum to zero, the external magnetic fields of all wires following the same path will cancel. All the wires of one circuit must pass through the same metal conduit, or an eddy current will be generated in the metal that will heat the metal and waste power.

If the return current were to follow an indirect path, say via the earth, then the transmission line would become a large loop with a high inductance. That would obstruct current flow in the circuit.

The energy propagated along a transmission line is guided by the currents in the wires and the electric potential between the wires. The Earth or ground is not the path of least impedance because it is not part of the balanced transmission line.

 

[Svein]

As I have mentioned several times, the classic power distribution in Norway (in power terms called IT) has no good reference to "ground". "Protective ground" is something the house owner is supposed to supply (usually a copper wire buried inside the concrete foundation of the house). The "neutral" is a fictive voltage at the center of the three-phase distribution.

I have to mention that we are slowly converting to four-wire power distribution (three-phase "star" with the center of the star playing the role of the "neutral" phase. Hopefully the potential difference between this "neutral" and the "protective ground" is not to large (but I would not bet on it).

 

[artis]

Well the term "neutral" is sort of misleading I think personally. For a balanced 3 phase system as long as there are no faults indeed the current is distributed among the 3 phases, but in a single phase system at least one that we have here in EU the neutral is essentially a power conductor. After all current must get back to source somehow...
it is often that one can find some voltage on the "neutral " line in apartment blocks as we are powered from a 3 phase Y system and the individual single phases are then routed to individual apartments, although as one can imagine the load is never equal on all 3 phases in such a configuration.

So here it is absolutely forbidden to tie "earth" or "ground" to neutral as that would result in a device which is often times energized to some voltage level on it's case. a dangerous situation.
maybe they tie the neutral to ground in the local substation, where they definitely have a good and massive grounding for lighting etc, but we definitely don't tie neutral to ground in our homes.

Well some people do but then again mistakes are always made.

I'm glad we have modern sensitive GFCI breakers as they switch off so fast it is more likely that in case of a fault or a shock hazard near water they would limit the current exposure time enough to save a person. in many cases simply a grounded device isn't good enough as not all grounds have low enough resistance to blow the breakers fast enough or at all.

 

[Guineafowl]

So here it is absolutely forbidden to tie "earth" or "ground" to neutral as that would result in a device which is often times energized to some voltage level on it's case. a dangerous situation.

Where are you, out of interest? In Europe, 3 phase Y is a standard distribution method, with the neutral/star point tied to earth/ground just before the meter (TN-C-S system). This puts each household into an equipotential zone relative to the neutral, and the neutrals rarely float more than a volt or two above earth/ground.

 

[artis]

Ok pardon , the problem with electrical distribution networks is that they differ from place to place and it's kind of complicated to keep in mind all the nuances around the world.

I live in Latvia, we are now part of EU for nearly 20 years. back in the day we were part of the USSR.
I'm not sure about all places in Europe but we had 3 phase star Y distribution since the very first power plants were built so for the most part of the 20th century.
As far as I know Europe also has mainly 3 phase Y.
But there is a difference, I don't know about most places in western Europe but here we almost never used earthing. Ground connections are only installed in newer built projects.
All buildings (except for purpose built ones like laboratories etc) that were built in the 20th century under USSR had 3 phase Y or single phase and no earth. So in my flat since I did not care to rewire the cables I only have 2 wires on each socket, the phase and neutral.

In each 380/400v local 3 phase substation there is a local ground to which the neutral is tied, so each transformer that is feeding each local suburb or block is earthed but only at the substation.

One reason this was done is because well it;'s cheaper. Why make cables with 3 wires for single phase and 5 wires for 3 phase instead just make 4 wires for 3 phase if necessary if not then 3 wires and 2 wires for single phase.
Also keep in mind we did not use breakers back in the day, each flat or private house had mostly ordinary ceramic boxed fuses. Those fuses were with a reserve ofcourse so even if you had a local ground that ground needed to be of very low resistance and the fault current very high in order to blow the fuse, and even if it did if you managed to touch the washing machine etc at that moment before the fuse was blown and if the ground fault was severe enough (like a bare phase touching the metal chassis) you most likely would have been dead anyway.
We had breakers of course back then but they were not used that often, also they were rather clumsy and the tolerance "varied" so for a house fire those breakers were good enough but for a "half short" to ground i wouldn't bet my money on it.
ps. I remember a case. years ago I was washing my hands in one place and I felt a tingling sensation with my wet hands, at first I couldn't understand what was going on, as I tried touching the water more and more I felt my heart beat changing and becoming arrhythmic. By that moment I realized I'm running live current through my body. the voltage wasn't high enough to shock me but enough to be felt. Turns out someone had tied the neutral to the ground chassis of the water boiler (probably thinking that he is grounding the damn thing) and sure enough there was some voltage in the neutral as often times there is.

 

[artis]

@Guineafowl Well I get the idea, if one has a good local ground and each neutral from each flat is tied to it then one can use this together with a good GFCI and the moment enough fault current will develop across any device chassis the breaker will trip because without a ground wire the GFCI will most likely only trip when someone touches the chassis, given it's fast operating time the person will most likely be ok but still the ground wire would act as a "stunt double" in the place of the person.
But as I said the problem is many places around the world don't have earthing and some that have are not good enough.

my 2 cents hope I've been of any use

 

[Baluncore]

"Protective ground" is something the house owner is supposed to supply (usually a copper wire buried inside the concrete foundation of the house).

The Earth connection should NOT be set in concrete, and should be buried deep in wet soil, next to and not under the building. A lightning strike that passes through conductors in concrete will crack the concrete due to explosive steam generation.

 

[Svein]

The Earth connection should NOT be set in concrete, and should be buried deep in wet soil, next to and not under the building.

Well - as the preferred building sites in Norway are on bedrock - how is that even possible? (that is why the traditional power distribution is IT).

 

[Baluncore]

Well - as the preferred building sites in Norway are on bedrock - how is that even possible?

It may come as a surprise but there are buildings on bedrock in other places beside Norway. The poles that support the distribution wires are set in the ground, so I see no reason why an Earth wire cannot also be set in the ground.
My house is on rock and has an earth-neutral link in the distribution board. I ran the ground wire in a crack on the surface to a hole drilled into wet rock. That met the conductance specifications.

... (that is why the traditional power distribution is IT).

The isolated earth, IT system used in Norway employs a surge protector between the star transformer neutral and the earth. IT was installed because it was cheap and had the advantage of greater up-time since a single phase fault to Earth will not result in dropping a breaker. After a phase fault to ground, the system will be operating as a fault earthed neutral, with two phases. The phase voltages are then the same as a 400V 3PH MEN system. The disadvantage of IT is that, due to insulation breakdown there is greater property damage by fire, and there is a greater shock hazard to people.

The historical IT system is expensive to upgrade because the three phase transformer voltage must be increased from 230V to 400V. Every switch board would need to be rewired to connect one side of each circuit to a newly added neutral conductor. That is why IT is still used.

The multiple earthed neutral TN system, used elsewhere in Europe, keeps the phase potentials closer to ground than does the IT system. I expect that new 400V 3PH TN systems being installed in Norway will have a multiple earthed neutral and meet the European standard.

 

[Svein]

The Earth connection should NOT be set in concrete, and should be buried deep in wet soil, next to and not under the building.

I have no opinion on this, I was just quoting Norwegian electrical regulations (as of around 2000).

My house is on rock and has an earth-neutral link in the distribution board. I ran the ground wire in a crack on the surface to a hole drilled into wet rock.

What is "wet rock"? Kidding aside, there are only three areas in Norway with soil that conducts good enough for short-wave transmitters.

 

[Baluncore]

What is "wet rock"? Kidding aside, there are only three areas in Norway with soil that conducts good enough for short-wave transmitters.

If what you are saying was true there would be more unhappy Norwegian amateur radio operators. A vertically polarised short wave antenna works best with a λ/2 dipole radiator, or a λ/4 above a radial wire ground plane. A horizontally polarised shortwave antenna is advantaged by a highly resistive ground since there is less cancellation by the inverted reflected image.
Only λ/4 vertical antennas for long wave, below 300 kHz, benefit from a conductive ground. That is why they are usually located on coastal salt marshes.

Back to the topic, your argument that Norway needs the IT system because it is largely made of rock ignores the fact that an Earth current only flows during a ground fault or lightning strike. For normal operation the circuit return current flows in the neutral wire, which is more than sufficient to trip the breakers on a fault. The IT system relies on ground connections at transformers which you seem to be saying is rarely possible in Norway.

The cost of the copper needed for a 3 wire, 230V, 3PH, IT distribution is greater than for a 4 wire, 400V, 3PH and earthed neutral.

 

[Svein]

Back to the topic, your argument that Norway needs the IT system because it is largely made of rock

Well, all countries are based on rock. The thing about Norway is that the last Ice Age scoured bedrock bare (my theory is that Denmark is largely made up from those masses the ice removed from Norway).

And - my last comments on power distribution:

• The town of Hammerfest (very far north) got electric power installed very early. The reason: Midnight sun in the summer but midday darkness in winter. The sun is below horizon from about 20th of November until about 20th of January.
• This may be an urban legend, but anyhow: When the town of Trondhjem was due to be electrified, there was a broad political discussion on whether to go for 115V or 230V. A political resolution was to go for the middle - namely 150V. Fortunately, the politicians did not have the last word...

 

[Guineafowl]

This may be an urban legend, but anyhow: When the town of Trondhjem was due to be electrified, there was a broad political discussion on whether to go for 115V or 230V. A political resolution was to go for the middle - namely 150V. Fortunately, the politicians did not have the last word...

Go for the middle voltage that no-one uses! Talk about sitting on the fence... A perfect place to quote Jim Hardy:

“The grid is a machine and when politicians mess with machinery they generally do it harm”.

Source https://www.physicsforums.com/insights/interview-instrument-engineer-jim-hardy/

 

[Windadct]

The issue of grounding for human / pubic safety is completely "political" - or relating to the Public Affairs. In the USA, OSHA, NEC (NFPA) and other agencies regulate these systems, they exist because the people wanted it.

Originally most if not all systems were ungrounded, there are still some legacy delta fed systems in the USA. In these system the priority was given to up-time or reliability, and to build in human safety was an added cost and complexity. IMO - human life is WORTH more today & we pay more to protect it. Years ago it was accepted that people died in the workplace or on the farm. We had 12 year olds working in coal mines and tanneries.

If the powers that be in a region did not want to pay the price to change or upgrade the system to protect human life, they did not. In some cases, they chose to use other protections, for example behavior (not good protection).

So, I guess my point is that the way these systems are has evolved over time, and there are human reasons for different regions having different philosophies. While you could say the systems are not optimized for operation, or you can say that the objectives in building these systems has changed.