Electrical current flow

[Constant Mesh]

Power Distribution

My home is served by an overhead single phase 7200 volt power line. It's a two wire circuit. An ungrounded wire on top and the grounded neutral below.

Assuming that the neutral is grounded at each pole as it travels back to its source in a local substation what path does the current take as it completes the loop?

If the neutral is grounded at each pole where's the potential difference to move the neutral current along its return path? Does all the current flow through the neutral or does some of it split off and return through the earth?

 

[odot]

This is a question best asked in a radiator thread........

jes' sayin' n' nuff sed....?

 

[Geezer]

I believe the ground (earth) and neutral and joined at some point. I am not familiar with a single phase service so I don't know where they might be joined. Everything I have seen is three phase at the pole and two phase coming from the transformer to each house.

 

[DENCOUCH]

Power Distribution

My home is served by an overhead single phase 7200 volt power line. It's a two wire circuit. An ungrounded wire on top and the grounded neutral below.

Assuming that the neutral is grounded at each pole as it travels back to its source in a local substation what path does the current take as it completes the loop?

If the neutral is grounded at each pole where's the potential difference to move the neutral current along its return path? Does all the current flow through the neutral or does some of it split off and return through the earth?

The ground is never considered a conductor like the neutral line is. The neutral line can deal with an imbalance between line 1 & line 2 if the loads are not balanced. Don't think of the current flowing back to the transformer... AC current switches direction of current flow in a completed circuit.

 

[ionbeam]

...My home is served by an overhead single phase 7200 volt power line...

Holy crap! Your oven should be able to smelt metal and your light bulbs should be very bright for a vary short length of time :dribble: I assume a step-down transformer between the pole and your breaker box.

How power is distributed is very specific to the area. To get all your answers you may need to talk with a local electrician. In general most residential power systems are single phase 120 and two phase 240. Usually two phase 208 is industrial.

In general, the neutral wire is not and should not be grounded. In all modern home power distribution systems feed and neutral come into your breaker box and ground comes from a local earth ground rod. In modern breaker boxes neutral is isolated from ground. A liability of this distribution system is that the neutral wire can develop 'nuisance' voltages. Modern breaker boxes with isolated ground and neutral are required in order to have ground-fault interrupters. GFI measures the balance of current between the feed and neutral wires, if there is any current imbalance it is because current is leaking to ground causing the GFI to trip, usually within one line cycle. If ground and neutral were connected together the GFI would be highly desensitized or more likely, would simply trip as soon as the breaker was turned on. The way the power circuit works is 100% of the current gets delivered through the feed wire and 100% gets returned through the neutral wire. Grounding in modern electrical systems is to shield enclosures, appliances and receptacles from stray voltages but is never part of the power circuit.

Edit: I see there has been some activity while I was typing. Odot is right (again) this sure sounds like a radiator thread to me. :lol:

Looking carefully to find the motorcycle content......

 

[BikerGeek99]

Peteytrons, man.

It's aboot them Peteytrons...

They're all ninja and ****. :assassin:

 

[beemerdons]

Peteytrons, man.

It's aboot them Peteytrons...

They're all ninja and ****. :assassin:

Finally the correct damn answer, Andy I just don't know why ionbeam Alan does not confer with you before he posts up his info!

 

[Redfish Hunter]

Peteytrons, man.

It's aboot them Peteytrons...

I am unfamiliar with Peteytrons. We had an outbreak of homotrons in New Orleans recently. Homotrons are bad about blowing fuses. :blink:

 

[Queensland Ken]

In some places in Australia, including areas around Toowoomba, the local authority use SWER distribution.

A single wire earth return, a good system that uses the mass of "earth" for the return current (AC current)

No good for linesmen or farm stock if there's a transformer fault, crook bonding or high earth resistance.

 

[Auburn]

...My home is served by an overhead single phase 7200 volt power line...

Holy crap! Your oven should be able to smelt metal and your light bulbs should be very bright for a vary short length of time :dribble: I assume a step-down transformer between the pole and your breaker box.

How power is distributed is very specific to the area. To get all your answers you may need to talk with a local electrician. In general most residential power systems are single phase 120 and two phase 240. Usually two phase 208 is industrial.

In general, the neutral wire is not and should not be grounded. In all modern home power distribution systems feed and neutral come into your breaker box and ground comes from a local earth ground rod. In modern breaker boxes neutral is isolated from ground. A liability of this distribution system is that the neutral wire can develop 'nuisance' voltages. Modern breaker boxes with isolated ground and neutral are required in order to have ground-fault interrupters. GFI measures the balance of current between the feed and neutral wires, if there is any current imbalance it is because current is leaking to ground causing the GFI to trip, usually within one line cycle. If ground and neutral were connected together the GFI would be highly desensitized or more likely, would simply trip as soon as the breaker was turned on. The way the power circuit works is 100% of the current gets delivered through the feed wire and 100% gets returned through the neutral wire. Grounding in modern electrical systems is to shield enclosures, appliances and receptacles from stray voltages but is never part of the power circuit.

Edit: I see there has been some activity while I was typing. Odot is right (again) this sure sounds like a radiator thread to me. :lol:

Looking carefully to find the motorcycle content......

One small correction: In electrical systems from 50v to 1000v (which covers houses) the electrical system is required to bond the nuetral and grouding systems together and the NEC 250.8 Connection of Grounding and Bonding Equipment (A) lists 8 methods acceptable to the code for connecting the two. It is required for all services. Typically it is the green colored screw that is connects a jumper from the back of your electical panel (that has the service disconnect in it) and a terminal on the nuetral bar.

The bolded above is only true for every panel down stream of the main service disconnect. For most houses the main service disconnect is the one in your house that has all of the breakers for the house in it. For every panel downstream of the main panel, you carry a ground wire and a nuetral wire along with the hot conductors in the same conduit or cable to the next panel. This is the panel that you keep the ground and the nuetral isolated from each other. The purpose of this is to prevent circulating currents in a fault condition.

Generally your GFCI description is correct. But there are two types of GFCI protection, one for people protection and one for equipment. The thresholds for the current imbalance to cause it to trip are different. It is higher for equipment.

EDIT: the above is the general rule, ther are exceptions, but you don't normally wire to the exceptions.

 

[SkooterG]

Hey! This is America! Come on you guys, speak English! I don't know what the hell language you are using but I can't understand a word of it!

 

[Usul]

Hey! This is America! Come on you guys, speak English! I don't know what the hell language you are using but I can't understand a word of it!

Let me translate: Constant Mesh wants to know how power travels down his pole. Dencouch says his load is imbalanced and ionbeam says he needs to put his rod in the ground. AuburnFJR says he needs to look in a book to figure the whole thing out. Odot thinks he's hot and needs to find a way to cool down. Simple.

 

[yamafitter]

There is a difference between bonding and grounding in electrical terms. Electrical bonding however should not be confused with the bonding agent used to bond the coolant tank to the body of the radiator on your bike.

Hope you enjoyed me bringing this back to a radiator thread.

 

[Chuck35]

Hey! This is America! Come on you guys, speak English! I don't know what the hell language you are using but I can't understand a word of it!

Let me translate: Constant Mesh wants to know how power travels down his pole. Dencouch says his load is imbalanced and ionbeam says he needs to put his rod in the ground. AuburnFJR says he needs to look in a book to figure the whole thing out. Odot thinks he's hot and needs to find a way to cool down. Simple.

+1

 

[DENCOUCH]

...My home is served by an overhead single phase 7200 volt power line...

Holy crap! Your oven should be able to smelt metal and your light bulbs should be very bright for a vary short length of time :dribble: I assume a step-down transformer between the pole and your breaker box.

How power is distributed is very specific to the area. To get all your answers you may need to talk with a local electrician. In general most residential power systems are single phase 120 and two phase 240. Usually two phase 208 is industrial.

In general, the neutral wire is not and should not be grounded. In all modern home power distribution systems feed and neutral come into your breaker box and ground comes from a local earth ground rod. In modern breaker boxes neutral is isolated from ground. A liability of this distribution system is that the neutral wire can develop 'nuisance' voltages. Modern breaker boxes with isolated ground and neutral are required in order to have ground-fault interrupters. GFI measures the balance of current between the feed and neutral wires, if there is any current imbalance it is because current is leaking to ground causing the GFI to trip, usually within one line cycle. If ground and neutral were connected together the GFI would be highly desensitized or more likely, would simply trip as soon as the breaker was turned on. The way the power circuit works is 100% of the current gets delivered through the feed wire and 100% gets returned through the neutral wire. Grounding in modern electrical systems is to shield enclosures, appliances and receptacles from stray voltages but is never part of the power circuit.

Edit: I see there has been some activity while I was typing. Odot is right (again) this sure sounds like a radiator thread to me. :lol:

Looking carefully to find the motorcycle content......

Mostly correct We do not use two phase current. In order to have 240v in a 3-wire, one uses split-phase current, where the potential is measured leg to leg. It was mentioned previously, there are times when the neutral & ground are joined, and this is considered bonding, as when a sub-panel is run from the main service panel.

 

[Bokerfork]

Personally, I don't care whether or not Ionbeam is totally correct,sorta correct or full of ****. All I know is he always sounds correct. Way more correct than myself, even if I'm speaking about things I know. Hell, I always thought American power was distributed in 3 phase. WTF?

 

[Redfish Hunter]

I am not sure that the original OP question was ever answered. We hit all around it and learned some good things but the question was,"What happens to the neutral current? Does it go to earth ground as it passes each pole or does it go all the way back to the substation?"

I was/am searching for the right answer to this without coming off like a complete idiot.

First, there is no "flow" unless there is a user within the home. Unless an appliance, a light or some electrical apparatus is turned on, there is no flow anywhere. Electricity follows the path of least resistance. The current being carried by the neutral should once it leaves the house go to ground. This is because the neutral and the ground are bonded upstream of the distribution panel and again at the pole. If I am wrong on this, I am sure that ionbeam or someone else will be along to correct me.

Here in Louisiana, the neutral and the earth ground are bonded inside the meter pan. We don't bond them downstream to prevent the possibility of circulation currents that were mentioned in a previous post. These circulation currents wreak havoc on the GFCI and the arc fault breakers.

On my little road there is a single 60,000 volt conductor which feeds the transformer and there is a neutral which is bonded to the ground wire at each pole. Yes, there are two 120 volt lines exiting the transformer.

Since this was posted in the Completely Off-Topic Discussion it does not really matter whether it is a radiator thread, an electrical thread, or a goat lovers thread. We have certainly discussed less important things more thoroughly than this. Since ionbeam has already had to correct some confusion on my part, my pride will not be too badly injured if he corrects me again.

 

[RaYzerman19]

Personally, I don't care whether or not Ionbeam is totally correct,sorta correct or full of ****. All I know is he always sounds correct. Way more correct than myself, even if I'm speaking about things I know. Hell, I always thought American power was distributed in 3 phase. WTF?

It is 3 phase, meaning 3 wires at the top of your local pole (ignore the bottom one for the moment), and your stepdown transformer is connected to one of the phases, meaning you have single phase to your transformer.... then out of the transformer, split phase into two 120's. Sometimes however in rural areas there is only one wire at the top of the pole, meaning you're so far into the boondocks they chose only to bring one phase to you from wherever they junctioned it off the three phase.

We could further confuse you by saying that some 3 phase systems are 3 wire or 4 wire...... but let's not go there.

 

[DENCOUCH]

I am not sure that the original OP question was ever answered. We hit all around it and learned some good things but the question was,"What happens to the neutral current? Does it go to earth ground as it passes each pole or does it go all the way back to the substation?"

SHORT ANSWER: No need for the current to flow to the sub-station, why? The power for your home comes from the line transformer that steps-down the line voltage to 120/240 volts.

Any measured current flow is only to that point.

Difference between 3 wire & 4 wire three phase power is easy to understand. The additional conductor allows the use of one of the line phases paired with the neutral for a lesser voltage. Phase-to-phase 480v 3-phase will now offer up 277v single phase. This 277v single phase can now be run through a transformer for 208v & 120v.

Three wire 3-phase is the best for motors & equipment as the motors run more efficiently & typically uses about 1/10th the power of a 120v motor of the same hp rating. The motor's windings being the same value, do not suffer from line imbalance (power loss factor), so no neutral is required. Changing the motor rotation is easy as pie... flip any two phases.

I forget anything?