Does the earth "complete the circuit" to become ground?

Look at high voltage transmission towers. Where is the neutral? Each power circuit is composed of three 'hot' wires. When at a substation, then three hot wires 'excite' wires on other side of that transformer. There is no direct connection. To understand how electricity gets from generator to that transformer, it arrives as voltage between three 'hot' wire phases.

Each phase is a sine wave. Each phase is 1/3rd of 360 degrees delayed from the next. A transformer can get voltage when connected between two hot wires from the generator. Yes it does get a wee more complex. Best to seek pictures of Wye and Delta connections before the 'wee more complex' details are discussed.

Generator outputs three sine waves - each delayed by 5.55 milliseconds (for 60 cycle power). All three are hot. There is no return or neutral from generator to substation.

The word transmit or conductive return means same here. Using earth as a return to a generator would create unacceptable losses for same reason as explained in telegraph / telephone example. Generator connects to primary side of transformer completely different from how secondary side of transformer connects to the house and earth ground.

Furthermore 'ground' is confusing. Which ground? Earth ground is only one ground in an electrical system.

Apparently your questi> w_tom coughed up:

High voltage long distance towers that cut over mountains in a wide path are three phase and are typically 230K v, 500K v, or 765K v. Lower voltage distribution lines are 69K v and

The practices how "high voltage lines" vary somewhat from country to country. The two wire "high voltage lines" consist generally of phase and neutral wires. You can think them as power feed and return wires.

There are "high voltage lines" that have three wires. Those are used to transport three-phase power (three 120 degree phase shifted lnes) without neutral.

The very high voltage lines that transport lots of electrical power tend to be three-phase systems because it is better for energy transport (less losses per transported kW is a good reason, and they have also other good properties). Three phase wiring is the norm when voltages are from tens of kilovolts to several hundred kilovolts. And three-phase is also used on many countries widely at lower voltages (three-phase power is common in many European countries).

Single phase two wire "high voltage" power distribution is often seen in the USA in the lines that feed the power to the distribution transformers that feed that 110V / 220V power to the building. The voltage on those lines is generally several kilovolts.

Look at it simply, the power station is a transformer, the primary is the generator, and the secondary is the long wires going to your home, your home is also a transformer which its primary is feed from the power plant, the secondary is your application voltage. a 2 wiere system, BUT, a ground is needed and each negative end of the generator is tied to a large ground rod at the power station. If the power station wasn't grounded the 230VAC on the secondary of the generator could float up thousands of volts above ground, so you could have 10,000 volts on the negative and then 10,000+ 230V on the hot side, the ground ensures that the voltage is always and only 230V above ground. If it wasn't grounded then the secondary of the generator would probaby melt itself together due to the offest in voltages within.

The ground in your home does the same, I personally thing is very bad when equipment don't use the ground at all, the result is you have your 230volts grid voltage, then your equipment is floating probably 1,000 volts above ground, it will only ever see 230volts, but if the equipment isn't connected to earth then if you touch a earth line (such as a radiator) and then touch the casing of a electronical equipment then you will get a shock. I have this problem all the time when equipment isn't earthed. From one end of the house I have a video player which isn't earthed, and a some hi-fi in another room which isn't earthed, one will be floating 100VAC above ground, the other probably 500volts above ground, if you touch the 2 cases you have then 400VAC across you and you know it!

The ground is the referance point to which the 230VAC goes on top of, you will always have 230VAC but in terms of ground levels you can float up as high as 10,000VAC or probably even more. This is why there are laws that all metal work must be grounded.

Chris

exxos coughed up:

Yes, thanks. The notion of floating voltages is not one unknown to me. Without a point in space, it can get goofy as to the precise potential of /anything/. AIUI, voltages have true meaning when compared to something else. I learned much of this by studying how certain parallel (non-pc) ports were designed to have every signal line accompanied by either it's own reference ground, or by that same signal 180° out of phase. No other point in space needed for those.

A side note, if you can confirm this. A former roommate of mine told me of a battleship he was given a tour of. Deep in the bowels of the thing he came across a section where there were huge generators essentially bolted to the inside of the hull. Their purpose was to de-gauss the ship, which builds up charge just by being a chunk of metal moving continually throughout salt water.

Also, I know that a helicopter coming in contact with a ship sometimes has to worry about potential differences.

Can you confirm any of that?

Thomas G. Marshall coughed up:

...[self-snip]...

Come to think of it, we called it that, but it's more a figure of speech at that point, since it's not a fixed-frequency a/c signal. The 2nd line would probably be the /inverse/ of the first (?). I forget now----s'been 18 years...

...[rip]...

I had this convo of alike a little while ago, backups up by someone who worked on helicopters, the air ambulance was the one which caught my eye, since the the thing is in the air is has a floating potential which could be anything upto about 500,000 volts, and when the doctor drops down on the metal rope, when his feet touch "ground" his feet have the voltage from the helicopter travel to ground via him! so he gets a nice shock. The other example is when the army lift those large metal containers, the guy ontop who is hooking them up gets a nice shock also and the potential of the helicopter is grounded. there was a very nice documentry of this a few years ago on TV.

Bascially anything which isn't hardwired to the "earth ground" (meaning earth itself) will build up a voltage. Of course it will want to flow to ground as its a static charge. Even a sky diver will probably be few thoustand volts above ground, though he will never get zapped since the closer he gets to ground the less the charge will be.

There has been many tests about this, Bill B might have some stuff on this on his site about it. Bascially the earth acts like a capacitor, the earth itself is the negative plate and the ionasphere is the other plate. A nice idea that your living in the middle of a huge capacitor ;-) I'm guessing though I think Tesla worked out there was something like 500,000 volts between plates, I think capacitance was about 30PF ? I'm guessing there, but the fact remains.

Best to keep both feet on ground and not move or touch anything just to be on the safe side, well apart from if you get stuck by lightning, that would be a bummer ;-)

Chris

I'm not going to get into phases and such too much, though if you have a center taped transformer, ground is the center, so you dont have the voltage float problem, one side will be 180deg possitive in relation to ground, the other side will be 180deg negative in relation to ground, thats 2 voltages you have, ground is ground on one side and ground is possitive on the negative side. You also get a voltage across the neg and pos also, though you get double voltage, since one is below ground and one above ground, now if you have 2 loads in series accross that rail, then the centre point between loads will in fact be 0 volts (if you balanced the loads equally) it will basically be at ground level but with nothing to tie it to ground its floating.

A neon sign transformer is a good example, center taped ground on the secondary, so you get +5KV GND -5KV. if you leave the ground connection off the the whole secondary will float up a few thousand volts, since the nearest ground is the 230V primary it will arc over and thus kill it. Some just tie the negative end of the secondary to ground and tie that to the negative of the primary also, but then you have 10KV between the secondary and primary, greater strain on the insulation then using a center tapped one.

Getting off topic a bit though now, If you checkout split supply rails then that will explain it all better. Chris

Well, *thank you* to all who replied! I appreciate the patience, explanations, etc.

My next questions concerning the lowest level regarding quark interactions to possibly actually "induce" the need for circuits to be complete will probably be pointed to one of the physics newsgroups.

In any case, you've all added quite a bit to my understanding, filled an olympic sized hole in my understanding, and that is very /very/ much appreciated.

---------------------------- Yup, most of the large high-tension towers are three phase, that is the most efficient transmission modality. There are three conductors. They are usually arranged in an equalateral triangle for inductive and geometric voltage symmetry.

-Steve