I know that electricity doesn’t just dissolve in the ground, it must return to the power source. But once the electricity is in the grounding device, how does it find its way back to the substation if it can be relatively far away?
Edit: I know ground isn’t used in normal working mode and where I live there’s no grounding in sockets.
In: 469
Grounding, meaning the actual use of a rod in the ground, is used to tell everybody what we are calling 0 volts. We have to do this because a measurement of voltage is relative to something else. For example, a 9V battery measures 9V across its terminals but will not measure 9V if I measure it to the actual ground (dirt).
The path to ground is not normally in the electrical circuit that powers your house. Wires between your house and the electricity generator (power plant, etc) carry the electricity. What your local ground is used for is to provide a better path for electricity to flow than to flow through you (shock you) if something goes wrong. The housing of all the electric things in your house (stove, microwave, etc) are connected to ground so that if something breaks, then the electricity will want to flow that direction instead of through you.
In modern power distribution, we use 3 phase power. Even though your house may only have 1 phase, Somewhere back from the power lines its derived from a 3 phase substation.
In 3 phase power, each phase is running alternating current, and they are separated by 120 degrees. This means that the phases “pushing” power (positive part of the sine wave curve) is equal to the phases “pulling” (negative part of the sine wave curve), so that the 3 wires are both simultaneously providing the “hot” and the “neutral”, letting current travel in both directions. That’s not a technically completely accurate explanation of how 3 phase power works, but its an ELI5 explanation.
[This GIF might help](https://gifdb.com/images/high/three-phase-motor-running-electricity-4k2dfqnufs3knhi7.gif).
They still have a ground wire, but its only really to reference the power to ground potential, there is not a significant amount of current that flows in or out of the ground. While the neutral wire in your electrical panel at your house is tied to the ground, the current doesn’t go into the ground, it travels back to the substation through the neutral wire, or if the split phase power is balanced, all the power is transmitted through the 2 “hot” wires.
However you CAN use the ground as a current carrying conductor. This was commonly done 100+ years ago with telegraph systems, but there are pretty serious limitations with it. For example in the American Civil War and WW1, it was common for telegraph crews to run a single wire and then stick an electrode in the ground to communication between field stations. To my knowledge there was never any widespread power distribution system that used ground as a current carrying device.
> I know that electricity doesn’t just dissolve in the ground, it must return to the power source.
This is like saying that the water a river discharges into the ocean must return to the mountains where the river originated. It’s kinda theoretically true but in practice it doesn’t really matter. The Earth will be able to absorb the current – in theory a DC current would charge the Earth until current stops. In practice the Earth is huge and can absorb a hell of a lot of current while it’s charge remains negligible. It will return some current to the substation or generator so it truly does stay neutral. This almost certainly isn’t the same actual electrons or holes – just as the water raining down on the mountains probably isn’t the same as what discharged out of the river recently – but things stay in balance nonetheless.
>I know that electricity doesn’t just dissolve in the ground, it must return to the power source. But once the electricity is in the grounding device, how does it find its way back to the substation if it can be relatively far away?
Individual electrons dont “need” to find their way back to the source. They’re not sent from a generator to your lamp to be consumed like food and sent back to be recycled. Electricity is like a game of musical chairs in your high school gym. The wire from generator, to your house and back, is like the ring of chairs. As long as the music plays(voltage), electrons move around. When the music stops, individual electrons don’t care where they are they just find the closest chair(positively charged atom) to sit in. In the game when you don’t have a chair to sit in, you’re out of the game. So you walk over to the bleachers and have a seat. Ground is a path to the bleachers. Out of the game but it’s still an empty seat available for you to sit in.
Electricity flows sort of like how water flows, from an area with a lot of it to an area with less of it. It can move along whatever path you give it, but it will always only flow downhill, from high to low.
“Ground” is like a drain for electricity. It will always be lower, so any overflow will always be safely drained away.
Ok, here’s a real ELI5 answer.
All the little electrons like to spread out as much as they can. When there’s a special place where electrons can go to spread out more than they can in the earth, that’s called “positive” – think “it’s a positive place to be for an electron so they want to go there.”
When there’s a special place where the poor electrons are more cramped together than they would be in the earth, that’s called “negative” – think “it’s a negative place to be for an electron so they don’t like it there.”
“Conductors” such as certain metals and other substances are like little roads the electrons can run through to escape negative charges and get to positive charges.
The earth is considered neutral because it’s sooo big with soooo many electrons in it compared to our power sources that it has plenty of electrons ready to run to your positive sources and plenty of space for electrons mashed together in your negative sources to run to.
Grounding is when you make a special road to the earth that electrons can use to get to the best place they can for themselves.
Edit: Added explicit definition for grounding.
sorry, there are some attempts to describe grounding, each one good to some degree, in the end too complex, missing the ELI5 point.
I’m neither physicist nor electrician (nor native english speaker), let me have an attempt, please downvote if wrong!
(i’m gonna repeat things that others said because they are correct)
The Earth works like a big dumpster for charge. It has basically zero charge, and because it is so big and massive, you can put basically endless charge into the earth, without changing the “zero charge” noticeably.
(probably not true from an advanced physicist’s pov, i’d be interested to learn more. But enough to explain our earthly problems.)
So the Earth is a massive Zero charge ball.
Electricity works in a way, that if there is higher charge at any point and lower charge at any other point, and if there is a connection between those two points, the higher charge immediately flows towards the lower charge point until they both are equal.
If you touch a power cable (the positive, charged line of a power cable), and you stand with your feet on the ground, you become the connection between the point of high charge (cable) and low charge (earth, massive zero charge ball), therefore the electricity will flow through you to the earth.
(the following is probably not true for other electrical proportions, but in our example of a massive power grid with huge powerplants vs. a human touching cable and earth:)
without any security measures (fuses and such) the source of power (the power plant) does not care, if the power that flows, comes back to it or if the power flows into the earth. it is like an open water pipe, it doesn’t care if you hit the bucket or if you spill everything on the floor, it just keeps pushing.
(this is why an GFCI-switch is important: it notices that the electricity is not flowing back to the source (difference between out and in), but goes somewhere else (the earth) and shuts off!)
And now, finally, what does the grounding do? the grounding is a third path for the electricity. (first path: from power plant to where it is needed (for example washing machine), second path: from where it is needed back home to the power plant)
the third path, the grounding, is a path from the place where electricity is needed (washing machine) to the ground / earth (massive zero charge ball).
Because: if any malfunction happens inside of your washing machine and something inside or the second path back to the power plant is broken, the power plant still pushes electricity into the washing machine (because the power plant doesn’t care), but it cannot flow back, so the electricity waits there.
if you now touch your washing machine (outside metal cover/parts), you become the connection between the high charged point and the earth, so you will be shocked by the washing machine.
the third path – the grounding, connects the metal parts of any device like your washing machine with the ground so that when an malfunction happens, the electricity flows right into the ground and does not wait there until you touch the machine and get shocked.
Electricity can just “dissolve” into the ground, although a more accurate term is disperse.
The power stations run on AC, or alternating current. That means the electricity is switching directions within the wire constantly. It does this because the electrons are essentially being pushed and pulled by a giant coil of wire passing by giant magnets. So the grid is not relying on the potential between it’s positive and negative to encourage electricity to flow like you would see in a battery. It’s using the strength of the magnetic fields to move them.
Electricity is electrons, which are all negatively charged, and they want to get the heck away from each other and spread out and it will seek out the path of least resistance to do so. The electricity is contained in the wire, but there’s a potential difference (high energy to low energy) between that wire and everything else. This potential encourages the electricity to want to spread out to everything it can. This is generally prevented by the wire insulation.
But what happens when the insulation fails or someone plugs something in they shouldn’t? Electricity will quickly look for new paths to spread out. You, the appliance, the walls, the copper piping, etc.
What grounding does is offer a very convenient path for electricity to disperse into the earth, away from things you want to protect. This does two things. It protects objects from absorbing electrical energy, which could be enough to light them on fire (or kill you), and also allows for a spike in the current flow which will trip the main circuit breakers and cut off the electricity completely.
It does, with lightning and radio signals.
I think the loose terminology in this thread is causing a lot of misunderstanding.
The term “ground” refers to the ground state of an atom. This is how you say an atom is uncharged. Ground conductors are current carrying conductors that are held in this ground state by being connected to a current sink that dissipates any charge. By charge I mean voltage or “electrical pressure”.
The dirt outside can be used as both a current sink and current carrying conductor. In most AC power systems we bury a rod in the dirt called the “grounding electrode”. This establishes a zero volt reference that is the same voltage as the human standing on the dirt. This makes sure that there is no electrical pressure difference between the human and the dirt. It also redirects any lightning strike that hits the electrical system to it’s target, the dirt.
This rod is attached to “grounding conductors” that distribute this reference to all the stuff humans touch. These conductors also make sure that if a wire comes lose inside any metal box that is connected to the system the box doesn’t become charged. Also, since there is a low resistance path back to the source of voltage, current can flow unimpeded in this “fault condition” and the circuit breaker will trip and prevent the building from burning down.
The third and final part of the earth grounding system is the “bonding location”. This is where a lot of understanding goes sideways. The bonding location serves 2 purposes. It attaches one of the conductors coming from the power transformer supplying power to the dirt physically close to where the electricity will be used. This creates a return path to the transformer that is “0 volts” called the neutral. It also creates a return path from the earth grounding system to the source of power allowing for that low resistance path mentioned earlier.
This means that if a human grabs a live conductor there is a return path through the dirt they are standing on. The current doesn’t just dissipate in the dirt because the nearby ground rod is applying an electrical pressure to the dirt that is the exact force to counter the pressure applied by the charge traveling through the human because the bonding location is connecting them together. This means the lowest effort place for the current to go is towards the ground rod.
I haven’t seen this many bad answers on a post in a while. Not that they’re wrong, I just don’t think they’re answering your question.
1) AC vs DC
DC or Direct Current is a battery where charges are actually flowing through the loop. Water in a pipe and all that
AC or Alternating Current is more like waves on a beach that go in and out. Your house uses AC electricity
2) Relative Ground
“Ground” is just zero potential energy. On a battery it’s the negative side, on an AC circuit it’s the return wire. Potential energy here is a lot like gravitational potential energy. if you set something on the table it’s not going to fall through the table. In that state it has zero potential. But it has a “larger” zero than something on the floor; after all of the table disappeared the object would fall. Relative ground is kinda like that: it’s relative to the system and “zero” is whatever energy you define it as. You could also think of it kinda like temperature, where 0°C is “larger” than 0°F.
3) Common Ground
When different devices have different zero levels, it creates problems. The two wires in your house create a loop, one feeding electricity and the other being a common ground wire, aka neutral. But why do we call it neutral and not ground?
4) Earth Ground
Earth Ground or True Ground is absolute zero. Going back to the temperature analogy, if your neutral is zero Celsius then the earth ground is zero Kelvin (absolute Zero). It’s an energy sink. Now, in your house earth ground isn’t directly connected to the hot or neutral wires (well, not OP’s house as they say their is two wire, but you get what I mean).
Earth Ground is a safety feature. In most applications that use it, the hot and neutral connect to the circuit while earth ground is connected to the enclosure. To get specific, let’s look at a lightbulb. Hot connects to the electricity flowing in, neutral to the electricity flowing out. Ground doesn’t connect to the bulb itself, but it is connected to the metal of the lamp. That way if something goes wrong and electricity starts flowing through the metal, all that electricity flows into the ground and you won’t get killed by touching it. And when we say “into the ground”, we mean it quite literally as there is a spike in the ground somewhere around your house the Ground wire connects to.
So there ya go. There’s no grounding on your sockets because it hasn’t been deemed necessary everywhere. There are all other ways to protect against the same thing an earth ground does, for example surge protectors and GFCI (Ground Fault Circuit Interrupt) outlets that will stop working if they see electricity going somewhere other than the neutral line. Fuses can also help, but by the time you’re pulling enough electricity to break a fuse some damage may already be done.
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