Electricity wants to go to ground?

[zappy]

I have always read that it wants to go back to the source to complete the circuit. Like back to the transformer etc.

I was talking to a guy at work, and he said that's not true because look at POCO's wires. There is no neutral, just three hots. So that got me thinking, if POCO's power is coming from generator's and one of there wires shorts, does it trip a breaker? Are there wires even protected by breakers or anything at all? Is POCO using the earth as a return path to complete the circuit? Thank you for your help.

 

[iMuse97]

I have always read that it wants to go back to the source to complete the circuit. Like back to the transformer etc.

I was talking to a guy at work, and he said that's not true because look at POCO's wires. There is no neutral, just three hots. So that got me thinking, if POCO's power is coming from generator's and one of there wires shorts, does it trip a breaker? Are there wires even protected by breakers or anything at all? Is POCO using the earth as a return path to complete the circuit? Thank you for your help.

POCO regularly, if not always, has OCP's (fuse links, breakers, etc) on their lines and other equipment. The Delta hook up of the xfmrs allows each phase to be the "return path" for the other phases, but there is usually a ground reference as well. The ground lines are at the top of the poles/towers all the way up to 765 KV.

 

[CFL]

They use multigrounded neutrals (grounded at every pole) and some current flows through earth back to source.

 

[Hv&Lv]

Tell the guy at work he is wrong. Distribution wires(The ones you see everywhere) have a neutral going back to the substation transformer. It It is NORMALLY below the three hot wires you were describing, 40 inches above the telephone lines and the cablevision lines. A neighborhood might have only one hot wire and a neutral. (IF they don't need three phase.) The high voltage lines that supply substations are generally a delta configuration.(No real neutral) The wires at the top of the towers are static lines.(basically lightning rods).
Not many one line diargrams show a neutral. That isn't to say that ALL systems have a neutral. A delta distribution system won't have one, but you won't see them often.

 

[iMuse97]

Tell the guy at work he is wrong. Distribution wires(The ones you see everywhere) have a neutral going back to the substation transformer. It It is NORMALLY below the three hot wires you were describing, 40 inches above the telephone lines and the cablevision lines. A neighborhood might have only one hot wire and a neutral. (IF they don't need three phase.) The high voltage lines that supply substations are generally a delta configuration.(No real neutral) The wires at the top of the towers are static lines.(basically lightning rods).
Not many one line diargrams show a neutral. That isn't to say that ALL systems have a neutral. A delta distribution system won't have one, but you won't see them often.

I knew if I put something up, somebody else would say it better, and I'd learn something. And what about overcurrent protection? Anybody? What types are used at what levels of transmission and distribution?

 

[Hv&Lv]

I knew if I put something up, somebody else would say it better, and I'd learn something. And what about overcurrent protection? Anybody? What types are used at what levels of transmission and distribution?

The substations generally have something along the lines of a VWVE recloser (google it) at the beginning of every circuit. There may be another three phase recloser down the line that is smaller and will coordinate with the recloser at the substation. AND/OR there could be three single phase reclosers. Each successive recloser will be smaller and will coordinate with the upstream recloser so as not to take out the entire circuit in the case of a fault. Fuses are installed at tap takeoffs, especially at all taps between the station and the first set of single phase reclosers.(don't want to knock out an entire circuit because of a squirell on an XF)


The fuses are classed and will also cordinate with other fuses and reclosers. One needs to look at and understand fuse and recloser TCC charts (or have a good computer program) for proper coordination so that a circuit doesn't go out or even a nuisance blink because of a non-coordinating fuse blowing during a fault.


the fuse sizes are a simple matter of doing the math. A fully loaded 25 kVa 120/240 with 14.4 kV primary needs at least a 2 amp fuse for 100 percent operation. We may put a 3 in or even a 6 to allow the XF to overload for cold load pickup.

 

[iMuse97]

cool. Thanks.

 

[Rick Christopherson]

I have always read that it wants to go back to the source to complete the circuit. Like back to the transformer etc.

What the heck, I am already labeled a heretic around here, let's go for the trifecta. hmy:

Electrons don't know where they came from or where they are going. They don't know that they came from a source and have to get back home before dark. :happysad: They only care whether there is a difference in voltage from one place to the next. If there is a difference in voltage and a path for them to follow, they will take it. That's all they care about. :bye:

Yes, in a closed path, electrons do want to return to their source, because that source represents the greatest voltage difference within their path. If you were able to provide them with a greater voltage, they would go there instead. But that's not as easy as it sounds.

 

[Besoeker]

I have always read that it wants to go back to the source to complete the circuit. Like back to the transformer etc.

I was talking to a guy at work, and he said that's not true because look at POCO's wires. There is no neutral, just three hots. So that got me thinking, if POCO's power is coming from generator's and one of there wires shorts, does it trip a breaker? Are there wires even protected by breakers or anything at all? Is POCO using the earth as a return path to complete the circuit? Thank you for your help.

The three wires are three phase as a rule. That's all you need to transmit three phase power. The sum of the three currents is zero. You don't need another return path. Distribution transformers usually have a ground on the secondary side. Again, that's to carry current through the earth. It's to fix voltage levels with respect to earth otherwise they could float at any potential.

 

[iMuse97]

What the heck, I am already labeled a heretic around here,

I appreciate the heretical views.

 

[ggunn]

I have always read that it wants to go back to the source to complete the circuit. Like back to the transformer etc.

I was talking to a guy at work, and he said that's not true because look at POCO's wires. There is no neutral, just three hots. So that got me thinking, if POCO's power is coming from generator's and one of there wires shorts, does it trip a breaker? Are there wires even protected by breakers or anything at all? Is POCO using the earth as a return path to complete the circuit? Thank you for your help.

Three phase and split phase power do not use a ground to complete the circuit; if there is a ground it's for reference only and there should be no current flow in the ground wire. Likewise, if there is a neutral it's only to carry the imbalance return current and if the load(s) is/are balanced there is no current in the neutral, either. In split phase when one hot wire is "pushing" the other is "pulling", and 1/60th of a second later their roles are reversed. Three phase is a bit more complex but is in essence the same.

In some three phase systems, one of the "hot" wires is connected directly to ground (corner grounded), and as counterintuitive as it seems, no current flows in the ground wire.

 

[realolman]

Many times the oil filled circuit breaker will reset itself twice... that allows faults - maybe falling branches - to clear themselves or burn off , and the power will be restored without any intervention by the utility company... on the third time, it'll stay off, and have to be manually reset by someone, after looking the lines over to make sure there is nothing wrong.

If you look near an overhead transformer, you will probably see something that looks like an open bladed knife switch, but part of it is round... about 3/4 of an inch in diameter and maybe 10-12 inches long. Those things hold a fuse that looks like a big spike with a tail of wire on the end of it.

When the fuse blows the "switch" falls open and hangs down... pretty easy for the POCO to see.

 

[Hv&Lv]

The three wires are three phase as a rule. That's all you need to transmit three phase power. The sum of the three currents is zero. You don't need another return path. Distribution transformers usually have a ground on the secondary side. Again, that's to carry current through the earth. It's to fix voltage levels with respect to earth otherwise they could float at any potential.

How can you supply anything other than a dedicated delta load without a neutral? Every three phase line we have has a primary neutral. I have never worked on a utility system without a primary neutral except for a dedicated delta load.(Usually to something along the lines of a rock quarry or a large mill.)
On a three phase system with various single phase loads, perfect balancing is impossible. With different loads coming on and off at different times, imbalance will always be a problem. It has to have a safe return to source.

 

[realolman]

How can you supply anything other than a dedicated delta load without a neutral?

Wouldn't this do it? Three single phase transformers hooked to three houses....please excuse the crappy drawing...I've been ill ( not true it's just a crappy drawing

 

[Hv&Lv]

View attachment 5900 Wouldn't this do it? Three single phase transformers hooked to three houses....please excuse the crappy drawing...I've been ill ( not true it's just a crappy drawing

Sure, but how many circuits have an exact amount of single phase loads. AND in your drawing, are the houses pulling the exact same load at all times?
My question was directed more to real world situations, rather than hypothetical applications. :lol:

 

[Rick Christopherson]

Sure, but how many circuits have an exact amount of single phase loads. AND in your drawing, are the houses pulling the exact same load at all times?
My question was directed more to real world situations, rather than hypothetical applications. :lol:

I am not sure how to address this because it is a rather lengthy topic, but neutral is not a "return". It is simply a name that we have given to one of the current carrying conductors. In the example he showed above, current that is leaving one phase will return on one of the other phases. As I said above, electrons only care about following a voltage difference. They do not know the name of the wire they are flowing through.

 

[don_resqcapt19]

If utilities stopped using line to neutral to supply transformers, we could get rid of a lot of the stray voltage problems. The voltage drop on the primary neutral is a major source of our "stray voltage" problems. There is no technical reason why you can't supply all transformers line to line, only economic reasons.

 

[Hv&Lv]

I am not sure how to address this because it is a rather lengthy topic, but neutral is not a "return". It is simply a name that we have given to one of the current carrying conductors. In the example he showed above, current that is leaving one phase will return on one of the other phases. As I said above, electrons only care about following a voltage difference. They do not know the name of the wire they are flowing through.

So there is no need for a neutral at all. Is this what you are stating?:?

 

[Hv&Lv]

If utilities stopped using line to neutral to supply transformers, we could get rid of a lot of the stray voltage problems. The voltage drop on the primary neutral is a major source of our "stray voltage" problems. There is no technical reason why you can't supply all transformers line to line, only economic reasons.

Ok, how do your 120 volt loads work in your scenario?

 

[realolman]

So there is no need for a neutral at all. Is this what you are stating?:?

In my crappy drawing the loads do not need to be balanced and the primary conductors would be smaller .... I don't think it's hypothetical at all