House voltage varying up and down

[SPIKER]

Beezfun:

Normally the Neutral only carries the UNBALANCED CURRENT back to the power company. The two HOT LEGS are out of phase by either 180 degrees or by 120 degrees. This depends on several things, the local municipality power company will be sending either three phase power down the road or single phase.

3 phase (120 degrees out of phase from A, B and C legs) will provide more power vs single phase. It is most common for industrial and larger power lines.

Depending on the transformer and utility company they can put a tap from leg to leg or leg to neutral to provide single phase off a 3 phase system. Typically in US they tap Leg to Leg for a dual voltage secondary so you have split phase in the home. (Where you measure 220v or 208v from leg to leg and 115v~110v leg to Neutral.)
On 180 out of phase power (typically single phase where there are 2 HOT LEGS and a center tap neutral) which is what most homes have. The lines at the road will have much higher voltages where they hit the Pole (or Pad) transformers.

The transformers step the voltages down to a useable voltage at the home/farm/factory. When the Neutral (center tap) got loose it no longer carried the Unbalanced Load back to the power company (or to the ground.)

So MOST of the power is a "Balanced Load" which means on the two sides of you load center has 2 legs. If you have 2 lights one on each leg, one is 100 watts the other is 70 watts, with them BOTH turned on the neutral is carrying only 30 watts (the unbalanced part.) the other 70 watts is traveling between the two legs across the Neutral but not back up it. This is why the voltages went wacky the odd voltage was due to the unbalanced part of the load driving the voltage either UP or DOWN depending on which leg had power higher vs the unbalance between them.

One thing I would suggest is you should also check out your own Ground Rod and the Neutral.Ground Bond in you load center. With this issue the Ground BOND SHOULD have negated most if not all of your issues. A DRY ground Rod or one which has gotten corroded, damaged or non-existent is something you should have looked at by a good electrician.

Mark

 

[BeezFun]

Beezfun:

Normally the Neutral only carries the UNBALANCED CURRENT back to the power company. The two HOT LEGS are out of phase by either 180 degrees or by 120 degrees. This depends on several things, the local municipality power company will be sending either three phase power down the road or single phase.

This is the part that's confusing for me . The two hot legs that are 180 out of phase are on the secondary side (house side) of the transformer. The high voltage line that's carried on the poles is single phase, at least in our neighborhood. In order for that high voltage line to power the primary side of my transformer, there has to be a return path for the current from the primary side. That's what goes down the neutral wire and back to the substation, although many people seem to disagree with that. I think I agree with you about my house unbalanced current also traveling on that wire, which means the power company does something back at the substation to handle that unbalanced load.

So MOST of the power is a "Balanced Load" which means on the two sides of you load center has 2 legs. If you have 2 lights one on each leg, one is 100 watts the other is 70 watts, with them BOTH turned on the neutral is carrying only 30 watts (the unbalanced part.) the other 70 watts is traveling between the two legs across the Neutral but not back up it. This is why the voltages went wacky the odd voltage was due to the unbalanced part of the load driving the voltage either UP or DOWN depending on which leg had power higher vs the unbalance between them.

Totally agree

One thing I would suggest is you should also check out your own Ground Rod and the Neutral.Ground Bond in you load center. With this issue the Ground BOND SHOULD have negated most if not all of your issues. A DRY ground Rod or one which has gotten corroded, damaged or non-existent is something you should have looked at by a good electrician.

Yes I'm surprised by this because there are three grounding systems that seem to have not done what I would expect. One is on my house, the other is on my neighbor's house, and the other is on the pole where the transformer is hanging. I put my ground system in when I added an addition to the house, I have 5 ground rods and one is laying underneath the footing I poured. The electrician suggested that because we have rocky dry soil. Everything is relatively new (5 years), connections are tight, acorn connectors on ground rods are all intact and tight. My only guess is that the grounding system is sufficiently high resistance that it left about 15v on the neutral wire, and that's the imbalance I saw.

 

[ThomasH]

Hi -

I think there is a little confusion here, as the ground rods at your house are there to bring the ground at your meter as close to earth potential as possible. Those ground rods are located way too far from the pole for much current to flow from them to the ground rod(s) at the pole. So they won't help if there is an unbalanced load at your house which is what you see with flickering lights. The rods at your house are only there to provide (if possible) an earth potential so that there is not a differential between a grounded device (typically an appliance) and ground. In other words, to keep you from being shocked if you are standing on a concrete floor and you touch a clothes dryer that is grounded.

 

[BeezFun]

Hi -

I think there is a little confusion here ...
So they won't help if there is an unbalanced load at your house which is what you see with flickering lights.

My problem wasn't caused by an unbalanced load because my neighbor had the same voltage variation across the two legs of his service as I did across mine. That leads to the conclusion that the problem is somewhere out in utility land, not in my house. I understand what each ground system is supposed to do, but the earth ground at my meter is bonded to the neutral in the service panel, and that's connected by a wire the size of my thumb to the ground rod at the pole which is about 200' away. Ditto for my neighbor's ground. So it's hard not to assume that these three ground systems act together in some way to try to pull the neutral back to ground. I think of them as three resistors making up a voltage divider as they each try to carry current to ground.

 

[aczlan]

I talked to my neighbor about this, he's an electrical engineer who admittedly builds video cameras not high power systems, but he says the neutral wire isn't carrying stray current, it's carrying all the current that comes down the high voltage line back to the power company. That makes sense to me, I can't see any way we could have a working system with only two wires if all the current flowing in one wire wasn't flowing back in the other wire. If we had multiple phases running along the pole I could understand sending current back a different phase, but that's not the situation we have.

That is the case on the PRIMARY or UPSTREAM (high voltage) side of the transformer.
On the SECONDARY or DOWNSTREAM (240v) side of the transformer, you have 2 hots (180 degrees out of phase) and a neutral. If you have a perfectly balanced load (10 amps on each hot leg) they cancel each other out and nothing goes back on the neutral line. If you have 15 amps on one leg and 5 amps on the other, the neutral is carrying 10 amps back to secondary side of the transformer.

Aaron Z

 

[BeezFun]

That is the case on the PRIMARY or UPSTREAM (high voltage) side of the transformer.
On the SECONDARY or DOWNSTREAM (240v) side of the transformer, you have 2 hots (180 degrees out of phase) and a neutral. If you have a perfectly balanced load (10 amps on each hot leg) they cancel each other out and nothing goes back on the neutral line. If you have 15 amps on one leg and 5 amps on the other, the neutral is carrying 10 amps back to secondary side of the transformer.

Yes, agreed. Spiker also pointed that out in an earlier post and was something I didn't think about.

 

[hr3]

Hi -

I think there is a little confusion here, as the ground rods at your house are there to bring the ground at your meter as close to earth potential as possible. Those ground rods are located way too far from the pole for much current to flow from them to the ground rod(s) at the pole. So they won't help if there is an unbalanced load at your house which is what you see with flickering lights. The rods at your house are only there to provide (if possible) an earth potential so that there is not a differential between a grounded device (typically an appliance) and ground. In other words, to keep you from being shocked if you are standing on a concrete floor and you touch a clothes dryer that is grounded.

SAY WHAT ????

 

[hr3]

Sub-Panel? What Sub-Panel? - 2. Electrical - Blog - Electrical -

This is what the grounds do,,, and it has nothing to do with unbalanced load...

 

[SPIKER]

ARGH dang register scanner kicked in and dumped my post & I had just gotten it to read easy & right...

HR3 and Thomas:

The OP issue is a bit different that what most people are thinking it is.

The Link one above me HR3 posted has a pretty simple schematic of a standard 180 degree single phase system. The OP's issue was more than likely at the "Jumper Link" between the "HIGH Side Neutral," High Side Neutral Main Wire" and or the "Transformer Bond." Also note copper thieves have been cutting off the Ground at the pole itself all over leaving a open dangling ground hanging from the pole. This can cause some issues for the High Side Neutral Conductor as they start to float out farther away from the utilities Main Substation Transformers due to overall resistance on long runs and overall unbalanced issues thru the neighborhoods. Same copper thief's will hop substation fences steal the copper & cause similar issues if they are lucky enough to cut one when the load is way down... luckily there are enough Darwin Award winners to keep this practice low.

When the Jumper or Ground at the transformer were lost / corroded it created a higher resistance and the Neutral Unbalanced Load Current created the unbalanced voltage. (Note Resistance to the flow of this current thru the neutral created a voltage variance as the OP seen when measuring between the Hot and Grounded Neutral in his & neighbors load centers/panel boards.)

NOW the OP's Grounded/Bonded Neutral SHOULD still have been "0-volts" (which it probably was or very close to it as he mentioned no issues were found with it.) The Ground Rods are used to do a couple different things one is to tie the local earth potential equal to the Neutral potential. This is for LOCAL (home/shop where Load Center/Service is panel is located.) The HOME can be a long ways away form the utility earth/bond which creates a voltage potential without the LOCAL earth ground rod connection.

The other one is to provide a short circuit protection where a fault happens. If a fault (short HOT to an appliance chassis) the current will trip the breaker near instantly as the Chassis is bonded to earth. Without the Chassis ground (two wire lamp for instance) the breaker may not trip leaving the appliance HOT waiting for someone to close the connection. That is IF the Neutral is not Bonded correctly and the lamp's Neutral is NOT bonded in the lamp's chassis. Anyone ever have an OLD (pre-1970's refrigerator?) Man those things were dangerous hehehe.


Now if a fault happens between a person and earth there is not enough current to trip a breaker (unless it is a GFI) which measures the current between the HOT and the NEUTRAL. If the OP has any GFIs in his house that had a "Turned ON/Working device" plugged in that GFI could have tripped as there was some unbalance between the hot & neutral vs ground..

Mark

 

[BeezFun]

The OP issue is a bit different that what most people are thinking it is.

Thanks for reading carefully and for the explanation. Everything you say makes sense and is consistent with what I see.