Stray Neutral Current along Wye distribution lines

[snflbruce]

Folks, please let me know if this is not the best forum for this thread.

In a very rural area with 7.2KV wye distribution (single phase plus neutral), I have measured low level magnetic fields almost 1/2 mile perpendicular the line that ultimately feeds about 50 homes with individual steel cased wells extending to the highly mineralized aquifer 400 feet deep. The fields don't fall off rapidly with square of the distance, which indicates to me that there is some current flowing back through the aquifer which is 400 feet deep.

In this area of 40 acre lots, each home has it's own single phase transformer, with the neutral distribution line jumpered to the secondary winding center tap.

To prevent the increase of this ground current, I'm thinking that new home's transformers should be configured as delta; using an overvoltage protector between the grounded secondary center tap (neutral) the primary neutral in case of a primary high voltage to secondary short. Thus each home site has essentially a separately derived neutral and no ground current will be generated except a small amount within that site between the grounding rods at the transformer, main meter panel, and well casing/pipe.

Since this seems like such an obvious solution to virtually eliminating stray ground current in rural settings, I'm wondering if I must be missing something. The only increased cost to the power co. is the overvoltage protection at the transformer secondary, and existing sites could be retrofitted over time without major wiring or transformer changes.

Anecdotally, I've rarely seen stray ground current problems (except on the local site) on Delta distribution systems, and homes in those areas without net current problems in house wiring will often have readings in living areas below 0.002 milligaus (yes, 2 microgaus) , the limit of my gear.

What am I overlooking?

Bruce

 

[karl riley]

Re: Stray Neutral Current along Wye distribution lines

Bruce, are you saying that you get power frequency magnetic field readings 1/2 mile in a perpendicular direction from a single phase distribution line (with neutral)?

What kind of readings, please. And away from buildings or in buildings? What meter do you use?
Have you taken regular measurements as you walked away from the lines?

I ask these questions because I think your explanation would be possible, but if I were there I would want more data to make my conclusions. I hope you will supply it.

Any neutral flow in the earth sets up a net current in the lines, which does not weaken with the square of the distance, but directly with distance.

I await your info.

Karl

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Mr Riley, I think I have your book and often recommend it for home net current corrections. Ten years ago it was a substantial help and in all likelihood saved my life. I was suffering from what was diagnosed as autoimmune demylinization of the brain, with concurrent viral encephalitis, which came on within a couple months of moving into a new home.

Ulitimately I found, much to my disbelief as a former EE, that wiring errors causing fields about 15 mg in various living areas were primary aggravators of my condition, and correcting them stopped most of the excruciating head pain and subsequently significantly slowed the progression of the disease.

Subsequent reductions, by reducing ground currents in particular, have brought an improvement in my condition, though substantial damage and epilepsy remains. For reasons I don't quite understand, longer exposures to low level ground currents (0.1 to .010 milligaus) seem to have a nasty latent effect, more than shorter exposures to higher fields. Thus I have done a lot of work on finding and eliminating ground current problems, and am horrified at the Wye system transmission line grounding practice. I have a number of unproven theories, but one pet which I hope to test this year is that ground currents either induce unusual biological frequency magnetic fields through some interaction with the earth's field, have biological frequency low harmonics, or perhaps alter the normal earths DC and 8 Hz field.

Yes, the land along this 7.2KV line is open grazing land- there are no connections on this line for about 2.5 miles. Measurements were taken perpendicular to the line at roughly 200 foot intervals. Readings varied up to 30% within a 5 minute period at any location.

Within 100 feet of the line, the field level was less than 0.5 mgaus. The field drops down in the first couple hundred feet, then drops very slowly for the remaining 1/2 mile. I'm interested in the 40 acre parcels along this distribution line for several disabled clients as well as myself, but am concerned that continued addition of new homes with wells on this service line will increase the ground current problem unless some change is made.

I have my own measurement gear consisting of a shielded 12" x 5/8" diameter iron rod with coil and a low noise (OPA37) amplifier connected to portable oscilliscope. I also use a modified version of Dr. Lee's Trifield meter with a "100x" external probe; this is the only commercially available unit capable of 2 microgauss sensitivity, though accuracy is not impressive. I use the latter for most field work.

More than you wanted to know. But regardless, thanks for your contributions to the field of EMF mitigation, and especially your outstanding work in reducing children's daily exposure in schools. I wish I could do more, but am only able to do very limited volunteer work.

In case you're wondering, I'm using a highly custom display (shielded rear projection) and keyboard, linked via fiber optics to a computer in another building 150 ft away, with filtered power and phone connections. I can forward a link to an article about this and low EMF autos if you're interested.

Bruce McCreary (rbmcc@cybertrails.com)
Snowflake, AZ

 

[hurk27]

Re: Stray Neutral Current along Wye distribution lines

Sounds like the MGN (neutral) on one of the poles has a bad connection. I would try to get the POCO to do a current reading on the MGN to see if there is any current on it. If there is none then the loads (transformers) are getting there return current through earth. this could produce a step potential at all the grounding if these earth grounds were lost through electrolysis

 

[bennie]

Re: Stray Neutral Current along Wye distribution lines

Visualize a MGN as one side rail of a ladder, the earth as the other rail. The rungs are the earth grounds.

Apply a current flow value on the MGN side rail, Apply resistance values to each rung and the earth between rungs. From this, calculate voltage drop, and resultant current in each loop.

You will notice a lot of circulating current. This is common mode voltage and current. This is why there is a lot of noise on MGN systems.

Until there is a method for preventing winding to winding faults energizing premises systems, the MGN system will be used.

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Bennie, It's my understanding that Delta configured transformers already in use present the solution to MGN's ground current problems.

How is the secondary winding protected from a high voltage primary short in the delta system?

And what's wrong with my idea of an overvoltage protector between the secondary winding and the primary side neutral, instead of the neutral bonding?

Bruce

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Hurk27, I agree that there may be a resistance/corrosion/connection problem on the neutral of this distribution line, since I have rarely seen magnetic fields extend this far from the line. I'll attempt to get our local crew to check it.

Still, it seems to me that the Wye distribution system is inherently a disaster from the standpoint of net neutral current, and I don't understand why the separately derived neutral of the Delta system isn't used, along with eliminating all but single point grounding of the neutral. This would be in effect a Delta configuration, but with one leg a neutral instead of another phase. Neither transformers nor lines would have to be changed, just the grounding.

If you show any analog design engineer a schematic of the Wye/MGN system, he would shake his head in utter dismay. It is an obvious, huge scale ground loop generating system, and power quality impediment as well, since no customer is actually transformer isolated.

I MUST be missing something, or is it just something that evolved 60 years ago and institutional inertia keeps alive?

Bruce McCreary

 

[hurk27]

Re: Stray Neutral Current along Wye distribution lines

I agree and I have heard the many reasons that they claim they can't do it.
But the simple fact is that I heard good no reason a neutral feeding a service drop has to be connected to the MGN that should be kept on the pole. While it's true many older houses still have no proper earth grounding and could be the reason they don't want to do this. But the requirement for earth grounding goes way back in the NEC and could be made mandatory (as far as grandfathering goes) if a change was enforced. as long as the earth electrodes at the service for a building is in place a primary to secondary fault in a transformer would still fault to the service electrode especially if the water pipe was used as an electrode. but as Charlie has said there fuse would not open fast enough to clear this type of fault so it would cause high voltage to be present on the grounding of the building. But now we have devices that could be added at the pole transformer that would shunt the current back to the MGN in this event and still keep the two systems isolated. I have had at least two times where the MGN was lost down the road from a building and because of the bond across the transformer neutrals this dead end run primary was using the buildings electrodes for the return path. This could be just as bad as a or even worse since it's not always discovered right away. and as the electrodes for the buildings are eaten away from electrolysis the touch voltage to the grounding on this building is rising ( one building had 56 volts to earth). But with a winding fault a fuse could be set to open in a fault and clear it right away. And with added TVSS across the transformer it would clear even faster. This would stop allot of ground loops between buildings that share common water pipes and CATV, and phone lines. But it wouldn't eliminate this when you have one transformer feeding several buildings. so I guess were back to square one.

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Hurk27,
I appreciate confirmation that a separately derived neutral on the secondary side isn't necessarily a safety hazard. I wish I could find a "bible" like (widely acknowledged) power transmission text book that would show Delta distribution system grounding practice. I think that might be key to "selling" an alternate grounding approach; since similar practice is already in use.

I'm not used to the type of power co. transmission engineers I've run into; all the engineers I've worked with are problem solvers, the guys I've talked to remind me of civil service dept. head types. (I was one of those, once, too.) My favorite: "we can't have anything nonstandard". Gads.

In our rural setting, it's all one transformer per home, but if multiple home transformers are set up with multiple secondaries, with the neutrals bonded together outside of the transformer, each customer could have his own separately derived neutral at his meter panel. If the neutrals are common inside the transformer, then net current between service drops is not completely avoidable. Gas and water lines would still need to be isolated, and CATV remains another issue that I'm not sure how best to cope with, since I haven't worked with them yet. (None of that out here in the sticks.)

Bruce McCreary

 

[bennie]

Re: Stray Neutral Current along Wye distribution lines

Bruce: I respect where you are coming from. You appear well educated.

Bennie's version of Physics 101;

All material is electrically connected. The degree of connection, determines where the major part of current flows.

When there is no direct electrical connection, there is both resistance and capacitance coupling.
The resistance coupling is through the air space. The capacitance coupling is across the air space.

Ungrounded lines are coupled to the earth by capacitance coupling. With the earth being a common lumped impedance, there is always current flow based on the extent of the coupling.

Apply my ladder calculation but substitute capacitance values at each rung instead of resistance or inductance. You will see current on an ungrounded system.

 

[hurk27]

Re: Stray Neutral Current along Wye distribution lines

But Bennie With the MGN/Service neutral isolation this resistance/capacitance coupling would be at a very far less current as far as the premiss wiring goes. and with this isolation since current always returns to source (transformer) the current drawn on the service would only return via the neutral feeding it. But with the higher voltage of the primary the current can return through Earth and this if why I think the two systems should be kept separate

[ March 14, 2004, 03:14 PM: Message edited by: hurk27 ]

 

[Ed MacLaren]

Re: Stray Neutral Current along Wye distribution lines

no reason a neutral feeding a service drop has to be connected to the MGN

Are you suggesting that the use of a "ground tie", as we call it in this area, be discontinued?

Not in my back yard!

I don't want any (earth) grounding electrode, especially my service grounding electrode, to have to open the primary fuse. Don't you think that is a job for a solid connection?

Ed

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Ed, I wasn't proposing eliminating the ground tie safety function, but replacing it's function with a TVSS. (Gas discharge type overvoltage protection device, I assume.) I appreciate the lesson in terminology you guys are giving me. I also appreciate your healthy respect for the dangers of that 7.2Kv primary.

Thanks for the nice GIF showing the "ground tie", Ed. How do I add a GIF to a post here?

The local power co. supervisor (a good man) in fact mentioned that there were a couple delta configured lines in my area. Since these don't have the ground tie, I don't see the problem in using the same grounding approach elsewhere.

Bernie,

I agree with your physics, but not the significance of the capacitive contribution. The capacitace of a wire 30 feet(!) off the ground (not a great capacitive surface) just isn't that much (picofarads??), and 60 Hz doesn't capacitively couple all that well. The capacitance at the tranformers is significant, but capacitive leakage to the secondary derived ground shouldl not cause significant net current problems. In the scale of things, this is irrelevant compared to the amounts of ground current.induced by the Wye/MGS. Remember that in the area I'm talking about, every home has a 400-500 foot deep steel cased well connected to the neutral system. In all my site work, this has been far and away the largest net current path.

I agree totally with your resistive ladder analogy, and think that's a good way to describe the Wye system. I just don't believe capacitive coupling is at all a significant source of stray neutral current. In all my field work, removing the larger direct resistive connections to the earth has been sufficient to achieve extremely low ground currents, measured as under 2 microgaus 60 cycle magnetic fields.

Can anyone suggest some power transmission texts which would cover Delta system grounding practice?

How do I add a GIF to a post here?

Bruce McCreary

 

[hurk27]

Re: Stray Neutral Current along Wye distribution lines

Ed It wouldn't if the right equipment were to be installed.

Loose the tie from the butt plate connection to the secondary neutral then install a TVSS system in it's place. If the transformer has a winding to winding fault the TVSS will redirect it to the MGN. This will provide a low impedance fault path for the primary voltage. with out sacrificing the isolation of the service neutral from the MGN. Then the GE at the service would only be for lightning or accidental HV contact. With the system we have right now we have a lot of current incidentally flowing through many house grounding systems. This is one of the reasons for voltage on pool grounding. as I said before, if the MGN is lost at the pole the transformer will get its return current through you grounding electrodes. and as time goes by your grounding electrodes will slowly disintegrate leaving the full primary voltage on your house while this will not get this far it could. as someone will usually get a bad shock or an electrician will lift the grounding electrode or the water meter man will remove the meter. and we all know what happens then. There will be a new job opening for a meter reader. Someone said somthing about the primary blowing open the neutral or GEC to the service. I just cant see that happening as I have not seen a primary feeding a transformer fused much over 15 to 25 amps. will this burn open a #6 GEC or a #4 neutral? I know I'm not the most knolagable on this subject but there has to be a safe way to do this. Wasn't it paul from England in the old forum said that they don't bond across the transformers for this reason? If they can do it why can't we?

 

[hurk27]

Re: Stray Neutral Current along Wye distribution lines

Bruce
We must have been writing at the same time at least we think alike

To post a Image on this forum you have to have a web page that you can upload you image too then when you want to post it in you message just use the image button below the text box and enter the web address of the image. this also works for any image on the web but you have to watch out as some images are copyrighted.

 

[bennie]

Re: Stray Neutral Current along Wye distribution lines

All TVSS devices fail. They first fail in short circuit mode, then revert to open circuit.

Hard wire grounding is the only way to go.

 

[karl riley]

Re: Stray Neutral Current along Wye distribution lines

Bruce, I just got back to this thread and see that a lot of good discussion has taken place. Bennie has just given a strong opinion, which you can expect from Bennie. He keeps these discussions interesting and sometimes heated. (Bennie, it sounds like we both read the same books by Severs. I remember the ladder diagrams. Good books.)

Bruce, when you mentioned 40 acre tracts I thought Arizona, since I once signed a sales contract to buy a "back 40" way south of Tucson, well clear of the end of the power line. But someone told me of a Mexican bandit who liked to come across the border and raid homes. I backed out, only to hear later that he was in jail.

To get back to the subject, the Delta and Wye discussion is beyond my field, so let me comment on the magnetic field issue. I find your measurements to be very interesting, as well as your instruments, since I designed a gaussmeter (MSI-20, MSI-25, and the very accurate MSI-95. I no longer have any financial interest in these instruments). But I understand the 12" X 5/8" iron rod as a core for getting increased sensitivity, since I experimented with all kinds of cores and coils when I was developing the meter.

The problem with measurement in milligauss units is that you must achieve a flat frequency response through the frequency range you are measuring, which I did achieve with the MSI-95, which was 2% accuracy from about 50Hz to 400Hz (aircraft frequency), and -3dB up to 3kHz. Otherwise your measurements in mG are not true. The Trifield is notorious for not compensating for harmonics and hence gives wildly incorrect gaussmeter readings. It is also not a true three-axis meter, and careful tests I conducted in my lab showed that it gives different readings depending on how it is held. A true 3-axis meter will give the same readings no matter how held. But we can discuss this meter stuff later. Your use of the oscilloscope at least shows you what you are measuring.

The main comments I have now are:
1) If you measured 0.5mG at 100 feet, the net current field at half a mile would be approximately 0.02mG, which sounds like close to what you are measuring. (at 1600 feet it would be 0.03125 mG; at 3,200 feet 0.015625 mG.

This field level would result from the net current at the neutral of the primary of 8 amps. It is not necessary to assume the diverted neutral is flowing from the well casings at the remote buildings. It could all be flowing in the earth underneath the lines due to the ground rods there.

But this is easy to check by measuring the current on the grounding electrodes going to the well casings with a clamp-on ammeter, as well as clamping around the service drop and measuring the net current (all this was in my book, if you still have it).

We could discuss some of this stuff by private message if you would like, if it is too far off the NEC focus on this forum. Also, I may be coming thru Arizona in an RV this spring and would enjoy troubleshooting in your area. I miss those back 40s!

Karl

 

[bennie]

Re: Stray Neutral Current along Wye distribution lines

Karl: You are correct, I plagerized the ladder analogy. I wrote this statement before and gave Mr. Seevers credit.

His book "Ground currents and the Myth of Stray Voltage" is good reading.

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Karl, Yes, I'd be honored and I'd love to meet you if you're ever in the White Mountains of Arizona. I live outside Snowflake at 6000 ft elevation, south and about 30 minutes from Holbrook. Please drop me a line at rbmcc@cybertrails.com

Karl I'd love to have your equation for calculating magnetic field due to net current, that could be a big help. I have not seen a situation in this area like the distribution line in question; but I may go do some more scouting to find similar situations for comparison.

Bernie, I hear and understand your love for simple reliable solutions, but accepting lots of stray neutral current and it's health impact for me (and others including a bunch of hysterical cows) just isn't really a solution. Perhaps you have a better one? Since almost a third of the country is Delta configured, the safety need for the Wye multiple grounds seems overrated.

 

[snflbruce]

Re: Stray Neutral Current along Wye distribution lines

Mr. Seevers "Ground currents and the Myth of Stray Voltage" is an interesting but misleading read.

He completely ignored the magnetic field impact of ground currents. He's very proud of his testimony for power companies over farmers, too.

I have to wonder if his "ignorance" of magnetic fields was financially motivated, since the this was widely known at the time.

Not a hero of mine.

Bruce McCreary