Tube replacement saga - let's vote!

Tommy Boy

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That fence may have been powered by 120VAC but I’ll guarantee that the fence was at a couple thousand volts at very low amperage, deduced from your story. Very low amperage because you are alive to tell the story and your urine and body don’t have very high conductance to earth ground.

Put this under rant: The electric companies in this country (and all countries) cheaped out and only supply the hot wires in their supply lines. In the US that is ~120, 240, and 480 VAC available (it varies by location). The electric companies use earth (literally) as ground or if you will a return wire. If they had used another conductor as a return wire where the neutral wire in your house was connected to the return wire instead of earth ground at the service box, it would make electricity much less dangerous and save thousands and thousands of lives. - Rich


Wow – a perfect albeit scarey teaching moment. :open_mouth:

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Certainly not true in the UK. We get live and neutral wires running to the house. I doubt it is true in the US because if your return current passed through the ground and not a copper wire I would expect the ground to get warm around the electrode and your voltage to be all over the place. And at the local substation the ground connection would be sending thousands of amps into the ground.

In the US, neutral (white) wire is connected to the earth ground in the service box (the house one). The ground wire goes directly to an electrode burried in the earth next to the house or, in some cases a pipe in the ground. - Rich

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Yes but I am sure it must also return to the substation, or line transformer via copper. It certainly does here.

The Earth is a great sink for ground. I am not sure about the UK, but if you can touch one hot (blue wire?), and bare foot on ground (earth), can you get electrocuted? If so, then UK is same as US. I work on HV systems on vehicles. We always design systems with return wired and ground fault detection. You can touch the HV conductor with your feet in a puddle on bare earth and you will not even feel a tingle because you are not completing a circuit. - Rich


Yes you can electrocute yourself by touching live and ground if you don’t have a residual current breaker (modern houses in the UK have one). That is because neutral and ground are at the same potential and are bonded at some point. But we don’t rely on passing thousands of amps into the ground. There is a copper connection back to the nearest transformer, where it is usually stepped down from three phase with no neutral.

If you have an isolated supply, then yes you can touch one side of it but you can’t distribute the mains like that. Just imagine if a whole street of house were wired in parallel to a floating supply. The various leakage capacitances of multiple houses full of wiring and appliances would mean you could still get electrocuted by touching one line. The two lines would sit at roughly half mains. If somebody shorted one line the other would go to full voltage. It could go unnoticed but would be make the whole street more dangerous.

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I’ll let you have the last word, but if you are interested, you should look at how this works. - Rich


This is definitely not true in New Zealand, Australia or most of Europe. I’m certain it’s not true in the USA either. Most of the world now uses TN-S or TN-C-S with dedicated neutral conductors.

I’m not aware of any countries which regularly do without a dedicated neutral conductor, except for some parts of Norway which use a split phase IT configuration where neither conductor is earthed - however, even in their case, they are definitely not relying on the earth as a return conductor.

When you do use the mass of the earth as part of the circuit, you are heavily dependent on local weather conditions and geology for continued service, and you definitely won’t get consistent service year round. During drier parts of the year, a significant portion of the power delivered to your site will be lost in the earth-return part of the circuit, meaning the voltage you have in your installation will drop from 230V to 200V, 150V, 100V, or any arbitrary value. Single-wire earth return systems were used in the past and there are still a few of them in service, but they are only useful in wetter, saltier areas and even then have significant drawbacks.



originally linked site has been called click-bait and that is fair, so don’t click here for it.

Clickbait. Mental masturbation of the worst kind. Create a crisis.

Put in perspective it is the largest power system in the world. I’d expect it to fail more than any other country’s. It’s all about exposure.

5 million miles of wire, 150 million customers and 330 million users spread out over one of the largest land masses in the world as well.

No real information in this article. Nothing about the growth of the grid. Nothing about the median time of failure (to mitigate against the Hurricane Sandys that kill power for millions for days and bumps averages up). No quantification of factors that would prove relevance to their “informational” comparisons.

We could be twice as efficient at preventing power loss per capital or per power mile or we could be the worst. You’ll never know which from this.



Fat fingered on the phone :slightly_smiling_face:

Real content in my edit :grinning:

Kind of figured that.

IBT might have been a poor choice. It was the first result in a hasty search. I replaced it with a different link. My point was that we have a lot of stuff that was installed a very long time ago, and would never pass muster with current (!) regulations.

But would you agree that large sections of our grid is old and outdated? Antiquated, even?

How about one of these?

The wires coming out of the generation facilities are three phase. Transmission line three phase. Residential lines three phase to a point. Residential transformers have secondary outputs that are two 120V outputs and neutral tap that goes to the house. The house neutral is tied to ground at the service box and the neutral wire that goes to the transformer is also tied to the transformer earth ground. My point being that no actual ground or return ever goes back to the generator. The earth is use as the ground. That’s what makes electrical systems so dangerous. - Rich


Not meant to sound snide but an honest learning moment for me. I have worked on high voltage supply design and implementation for 15 years and I have never heard power distribution explained that way. Why does the neutral and ground being tied to earth make it more dangerous then being fed back to generating point?

Also you don’t ever want to backfeed a generator

Yes this is exactly what I described. The return current flows in the copper neutral line back to the transformer. There is no current flowing through the ground.

The three phase supply from the generator forms its own return path. The primary of the transformer will be a delta configuration and current flows from the phase with the highest voltage to the ones at lower voltages. There is no current flowing through the ground back power station.

The system is the same in the UK except the local substation produces a star connected three phase 450V supply plus neutral. A domestic house just gets one phase plus neutral and that gives 240V. The next house down the road gets the next phase and so on. That is why it is very dangerous to steal electricity from your neighbours as there can be 450V between the live feeds of two houses.

Tying neutral to ground locally is for safety so that your supply is not floating around at some arbitrary potential relative to the ground around you. It isn’t cheaping out on a copper connection as that is what the neutral is and that is what carries the return current.

The transformer isolates you from the incoming feed from the power station, so there is no need for that to be ground referenced to anything local. Indeed that would be bad if it was a long way away because fluctuations in the earth’s magnetic field due to solar storms will induce potential differences in long cables.

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My only point being…AC electricity uses earth ground…you touch a conductor, ouch shock…in some cases people die. Why? They complete a circuit (with the earth/ground). It doesn’t need to be that way. Simple physics. I know exactly the way it is and the way it could be. - Rich

Yes you can have a locally isolated supply. I use one for mains experiments and repairs and if I touch one conductor I won’t get a shock. But it is impossible to distribute an isolated supply to multiple homes unless each one had its own isolation transformer. Even then it doesn’t stay isolated because all modern switch mode PSUs have Y capacitors between live and earth and neutral and earth. That would cause an isolated supply to become balanced around ground. One device on its own doesn’t leak much current but a house full in parallel would. Multiply houses in a road would give enough leakage to kill you if you touched only one conductor. Both would be live at half mains, which would be 120V here. And that is as long as all the leakage was balanced and there were no faults.

And what if somebody’s equipment had a fault and put a high voltage on the lines? If they were floating nobody would notice until some insulation broke down or they touched one conductor and got electrocuted. It is actually safer to have everything ground referenced when distributing it across the houses in a road or even a single house. You know exactly where you stand then as the lines have defined voltages on them relative to your ground and your water pipes, regardless of what you or your neighbors plug in.

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