Volts leaking to ground rod

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Jadnashua

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Just like when measuring dcv, swapping the leads of a MM can make the meter read plus or minus...you have to be careful how you hook up O-scope leads - it all depends on your reference point. With 240vac, especially on an O-scope, what you use as a reference point can be more a function of safety. So, just like any tool, you have to understand how to use it, and what it is telling you. On US 240vac service, power alternates from running from L1 to L2 and back again at typically 60Hz, therefore, the phase, or direction of the current is identical on L1 and L2 at any one instant. It gets a little more complicated when you throw in the neutral, but only for 120vac circuits.
 

JWelectric

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I agree except for the bold bit. The neutral does carry the sum of the currents through the 120 VAC loads on each leg. If the magnitude of the currents through resistive loads on both legs are equal, the sum will add to zero-- because the two currents are 180 degrees out of phase.
The one thing you have correct is the part about single phase 240V and no one here is saying otherwise. You keep referring to "vector math", but are mistaken in saying that the (voltage) difference between two vectors is calculated by adding. You must subtract one from the other, not add.

Well at least we are in agreement on the fact that this is a single phase 240 volt sine wave. Now in all your wisdom show the math on how this single sine wave somehow splits into two sine waves that are 180 degrees apart.

Wait a minute I believe I have it figured out. I went to Hobby Lobby and bought me a yard stick that is 36 inches long but instead of getting one yard stick that is 36 inches long what I bought instead is two halves of a yard stick that are 18 inches long.

If I measure that yard stick from the middle I have one half that is 18 inches long and the other end of that yard stick is 18 inches long so I subtrat one 18 inches from the other 18 inches which by the two of you equals to me not having a yard stick at all.

There in one single phase present in a 240 volt circuit. What is not there and cannot be there is two phases going in opposite directions at the same time and remain one single phase. You are confusing the fact that if you are standing on a railroad track looking down the track and want to look in the other direction that it is you that has to turn 180 degrees to look in the other direction not the track that has to turn.

With the scope you are looking from N to A and also at the same time looking at N to B just like standing on that rail road track. If you would just stop and think about it for one second you could see that the scope is showing you both halves of the single sine wave at half of the entire voltage. Just like the batteries that are connected in series +-+- the scope is connected to the -+ half of the winding so one is showing a sine wave in its positive peak and the other is showing the very same sine wave in its negative peak. You are looking at one sine wave not two opposing sine waves.
 
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DonL

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Reach4

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Well at least we are in agreement on the fact that this is a single phase 240 volt sine wave.
hugep1a.png

In the schematic above, presume the primary winding on the left is powered by 60 Hz AC.

Measured with respect to gnd, is point A in phase or out of phase with point B?
 

Ankhseeker

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Screen Shot 2014-02-24 at 9.41.47 AM.png

ok, here is an image showing the out of phase relationships between the tapped winding. If I remember right, with a tapped secondary, the phasing is different because the start and ending windings are reversed due to the tap. Did I forget something?
 
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The latest report on this issue:

The power company placed a device between the meter and socket that they think will give them some information. I have not asked them yet to remove it and analyze the data.

I WAS there today for a moment. I placed my clamp on amp meter on the grounding cable, and found 0.7amp.

I shut off all power to the house via the main breaker, and the reading on the amp meter stayed steady at 0.7amp.

Me? I am saying that this is the power company's problem now. I think JW has it right: some current is leaking elsewhere and entering the system thru the copper water supply leading out to the road.

A strong argument for an electrically isolating coupling at the meter which is out in the parkway, here in town. That would leave nearly 25' of copper still in the ground to assist in grounding, and bond the plumbing in the house, but cut you off from your neighbors' issues, yes?
 
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Figure out whether the ground problem was internal or external, and then to call the power company to fix their lines.

Possibly you have missed the updates.

I did report that the power company replaced their service drop, and that the current leak remained. They put some sort of recorder in the socket and plugged the meter into that. I'll ask for a report from them soon.

Went by today, found 0.7amp going thru (not down!) the ground cable. Turned off the main breaker for the house and it was still 0.7amp.

I am of the opinion now that the power is coming up the ground cable, not down.
 

JWelectric

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View attachment 23678In the schematic above, presume the primary winding on the left is powered by 60 Hz AC.
Measured with respect to gnd, is point A in phase or out of phase with point B?
Take the bottom wire of the winding on the bottom and connect it to the bottom conductor of the top winding and you will have the very same thing our homes have, a single phase center tap system that is in the next post.

What you have is two independent 120 volt systems assuming that the device you have the conductors connected is a NEMA listed device. What you can’t get from this system is 240 volts therefore something very different than what is being discussed.

View attachment 23679ok, here is an image showing the out of phase relationships between the tapped winding. If I remember right, with a tapped secondary, the phasing is different because the start and ending windings are reversed due to the tap. Did I forget something?

I can’t see anything in this image that would lead someone to believe that anything is out of phase, in fact it looks to be in phase.
As labeled the start winding is starting at zero rising to a peak positive while at the same time the other end of the 240 volt winding or finish winding is starting from zero rising to a peak negative. As this voltage passes through the diodes the voltage is ratified to a pulsating DC voltage by letting the negative pass one diode and the other letting the positive pass.

Just like a battery while one end is positive the other is in phase by being negative. This must happen in order to have a difference in potential so current flows. The center tap or neutral point as defined by the NEC “Neutral Point. The common point on a wye-connection in a polyphase system or midpoint on a single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct-current system.”

It is neutral because while the start winding is positive and the finish winding is negative the neutral is just that, positive and negative at the same time. Should a 120 volt appliance be connected across the start winding while it was positive then the neutral would be negative to its respect. If at the same time an appliance of half the wattage as the start winding be connected across the finish winding While it was in the negative then the neutral would be positive to its respect but half the current of the appliance on the start winding would be across a 240 volt load and the neutral would carry the rest. The only 120 volt current to be found would be half of the start windings load. All of the current on the finish winding and half the current on the start winding would be across 240 volts.

Take two keylesses and connect them in series and to a two pole breaker. Install two 40 watt bulbs and energize. If the two 120 volt breakers that make up a two pole breaker were 180 degrees out of phase with each other something crazy should happen. Want to know what will happen? They come on just like any other 40 watt bulb, yes they do this without a neutral. Use a three conductor cable and use a two head flood with one on one side of the breaker and the other on the other side of the breaker. Flip it on and then remove the neutral and it is easy to see that the two 120 volt circuits are indeed in phase with each other.

Through that damn scope in the trash and spend a little time just thinking and one can see that the windings of a single phase transformer is turned all in the same direction. In most cases the secondary is not even a wire but instead a sheet of metal.


http://www.youtube.com/watch?v=fe4hs30LoGs
 

Bluebinky

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Wait a minute I believe I have it figured out. I went to Hobby Lobby and bought me a yard stick that is 36 inches long but instead of getting one yard stick that is 36 inches long what I bought instead is two halves of a yard stick that are 18 inches long.

If I measure that yard stick from the middle I have one half that is 18 inches long and the other end of that yard stick is 18 inches long so I subtrat one 18 inches from the other 18 inches which by the two of you equals to me not having a yard stick at all.
I think you're almost there. The centering yardstick you describe has both sides "in phase" so you can't use both sides at the same time to measure distance using the conventional method. If one side had negative numbers (opposite or "out of phase" from the other), then you could measure distance by subtracting. I'm not stupid enough to say that the actual distances would physically change or the yardstick would suddenly fold in half, but rather that is how math works...

I am curious. You've worked with 3-phase power before? Imagine a Y configuration. Aren't each of the legs 120 degrees out of phase with each other? If you added another leg with a phase angle exactly half way between two legs, wouldn't it be 180 degrees out of phase with something?

One more... if the two terminals of a battery are opposite polarity, then aren't two wires carrying AC out of phase with each other too? There is nothing special about a neutral conductor other than it happens to be connected to the dirt beneath us.
 

Bluebinky

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Possibly you have missed the updates.

I did report that the power company replaced their service drop, and that the current leak remained. They put some sort of recorder in the socket and plugged the meter into that. I'll ask for a report from them soon.

Went by today, found 0.7amp going thru (not down!) the ground cable. Turned off the main breaker for the house and it was still 0.7amp.

I am of the opinion now that the power is coming up the ground cable, not down.
To me, it still sounds like the problem likely involves more than the wiring in the house in question...
 

JWelectric

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[
I am curious. You've worked with 3-phase power before? Imagine a Y configuration. Aren't each of the legs 120 degrees out of phase with each other? If you added another leg with a phase angle exactly half way between two legs, wouldn't it be 180 degrees out of phase with something?
It doesn’t matter if it is a wye or a delta the three phases will be 120 degrees out of phase but the key word here is “THREE” not “SINGLE” which is a big difference. If we were talking about a delta system then one of the three windings could be center tapped and if the voltage of the delta was 240 then from one end of one of that single phase to the neutral point would be 120 volts. To the opposite end of either of the other phases and it will be 207.84 volts.
Should another winding be added between any of the windings then from this new winding to any of the windings which it divided would be 60 degrees out of phase.

One more... if the two terminals of a battery are opposite polarity, then aren't two wires carrying AC out of phase with each other too? There is nothing special about a neutral conductor other than it happens to be connected to the dirt beneath us.
I am not sure what you are asking here but if I understand the question I think you are confusing polarity with phase. A complete sine wave will have two opposing polarities, one negative and the other positive. The neutral is the center tap of the secondary which gives us 120 volts. The neutral is a current carrying conductor and the connection to earth has nothing to do with anything.

The only reason we connect to earth is outlined in 250.4(A)(1) of the NEC.
 

DonL

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The neutral is a current carrying conductor and the connection to earth has nothing to do with anything.


That is true After you have a Neutral. And the neutral is derived on the secondary of the split phase transformer.

We still have 1 phase 1 wire feeds here. And they will use the Earth Ground for the primary, on a 1000+ foot wire run.

The earth resistance in these parts let them do that, and save a bunch of wire.

The down side is that safety is compromised if someone disconnects a ground rod that is carrying current. May be the last time they do that, If they do not have the proper PPE.

This is what I think the OP is seeing, because current does not just come out of the ground. If it is you should bottle it and sell it on E-Bay.

The transformer could be bad. Or the Ground to Neutral is open on the Transformer. That connection is external to the transformer on many Pole Pigs.


Me Thinks.


Pole Pigs look small on the pole.

Pole_Pig.jpg
 
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Reach4

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From post :105:
View attachment 23678

In the schematic above, presume the primary winding on the left is powered by 60 Hz AC.

Measured with respect to gnd, is point A in phase or out of phase with point B?
Take the bottom wire of the winding on the bottom and connect it to the bottom conductor of the top winding and you will have the very same thing our homes have, a single phase center tap system that is in the next post.

What you have is two independent 120 volt systems assuming that the device you have the conductors connected is a NEMA listed device. What you can’t get from this system is 240 volts therefore something very different than what is being discussed.

Are you saying that you won't answer if point A in phase or out of phase with point B? Seems like a simple question. It is not a complex question.
 
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Jadnashua

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From post :105:


Are you saying that you won't answer if point A in phase or out of phase with point B? Seems like a simple question. It is not a complex question.

Your drawing is NOT a US residential power supply transformer (there two separate windings, and no common neutral). But, if you look at the dots drawn on the schematic, those show the phasing of how the thing is wired, and A and B are IN-phase, since they are both connected to the 'dotted' side of the secondaries.
 
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