# Poco



## RIVETER (Sep 26, 2009)

RIVETER said:


> Does anyone have a good pictorial of the utilities wiring hookup of the primary of a residential 7200v transformer?


Where are all of the smart guys this time of night?


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## Black Dog (Oct 16, 2011)

RIVETER said:


> Where are all of the smart guys this time of night?































:jester::laughing:


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## Black Dog (Oct 16, 2011)

RIVETER said:


> Does anyone have a good pictorial of the utilities wiring hookup of the primary of a residential 7200v primary transformer?






















Fig. 1.1: Multi-Grounded Comon Neutral (MGCN) 









Fig. 1.2: 3 Phase 4 Wire Distribution - typical in my area on older 4KV Circuits, and some newer 12470Y/7200 4 Wire Circuits









Fig. 1.3: 3 Phase 3 Wire "L-L" Distribution - typical in my area.

More images may be seen at Residential Distribution Systems page.


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## RIVETER (Sep 26, 2009)

Thanks for the info. My concern is, and I will say that I know nothing about "line" work, that I've been told that the utility ties one wire of the higher voltage to the transformer primary. Where is the other end of the primary connected?


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## Black Dog (Oct 16, 2011)

RIVETER said:


> Thanks for the info. My concern is, and I will say that I know nothing about "line" work, that I've been told that the utility ties one wire of the higher voltage to the transformer primary. Where is the other end of the primary connected?


There is no other end. It's just one wire.


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## RIVETER (Sep 26, 2009)

Black Dog said:


> There is no other end. It's just one wire.


That's where I'm at...WHY???


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## Bootss (Dec 30, 2011)

Black Dog said:


> Fig. 1.1: Multi-Grounded Comon Neutral (MGCN)
> 
> 
> 
> ...


So you just google that (or whatever electrical system) and the images come up?


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## Black Dog (Oct 16, 2011)

Lep said:


> So you just google that (or whatever electrical system) and the images come up?


Yes in fact, that search lead to this forum... http://www.electrical-contractor.ne...76613/all/Primaries_of_pole_mounted_tran.html


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## RIVETER (Sep 26, 2009)

What I am asking about is where is the PHYSICAL attachment of the other end of the transformer winding going back to the substation........I think we are in a learning situation here.


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## cabletie (Feb 12, 2011)

Well I hope I don't get blasted by the people that really know distribution systems but, I thought the other side was the case and it ties into the system neutral. The system neutral is the same neutral used for the primary and secondary, and makes it an auto transformer.


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## cabletie (Feb 12, 2011)

Okay time for bed. I will check In the morning to see how bad a beating me and my statement took.


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## RIVETER (Sep 26, 2009)

cabletie said:


> Well I hope I don't get blasted by the people that really know distribution systems but, I thought the other side was the case and it ties into the system neutral. The system neutral is the same neutral used for the primary and secondary, and makes it an auto transformer.


I suppose that I don't even know enough to dispute you but all EMF "comes and goes" to and from it's individual source. If a "yard", so to speak is delivering 7200volts to somewhere there has to be a return to the source...I think. I am not trying to be combative with you. I am old, but still learning.


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## Jhellwig (Jun 18, 2014)

cabletie said:


> Well I hope I don't get blasted by the people that really know distribution systems but, I thought the other side was the case and it ties into the system neutral. The system neutral is the same neutral used for the primary and secondary, and makes it an auto transformer.


It is not an auto transformer. That would be a very bad thing if the winding opened up.

On most utility transformers h2 and x0 are tied together inside the pot and the x0 and pot are connected to the secondary neutral and poco neutral.


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## dmxtothemax (Jun 15, 2010)

Are you refering to a S W E R system ?

If your not sure what SWER is ?

Google it .


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## oliquir (Jan 13, 2011)

Jhellwig said:


> It is not an auto transformer. That would be a very bad thing if the winding opened up.
> 
> On most utility transformers h2 and x0 are tied together inside the pot and the x0 and pot are connected to the secondary neutral and poco neutral.


that is the common config here, same for 3ph system also


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## don_resqcapt19 (Jul 18, 2010)

RIVETER said:


> What I am asking about is where is the PHYSICAL attachment of the other end of the transformer winding going back to the substation........I think we are in a learning situation here.


Look at figure 1.1 below the picture. A single conductor is used as both the primary and secondary grounded conductor.


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## MXer774 (Sep 1, 2014)

The cans my shop provides me is of the two primary bushing. H1 being the primary input. H2 gets bonded to the grounded line and the center tap on the secondary bushings. I know of no return back to the station or yard. Or was that not even close to what you were asking. If not then I apologize in advance.


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## Meadow (Jan 14, 2011)

RIVETER said:


> What I am asking about is where is the PHYSICAL attachment of the other end of the transformer winding going back to the substation........I think we are in a learning situation here.


ITs a grounded neutral.


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## guest (Feb 21, 2009)

Jhellwig said:


> It is not an auto transformer. That would be a very bad thing if the winding opened up.
> 
> _*On most utility transformers h2 and x0 are tied together inside the pot and the x0 and pot are connected to the secondary neutral and poco neutral.*_



On most , but NOT all systems. 

Primary systems can be configured just like our common LV systems, I.E> Delta, Wye, Open Delta (Extremely rare for a primary) or Single phase (One hot and one Neutral.) 

In a Delta (or open delta) primary, transformers will have TWO primary bushings and be connected phase to phase. 

In a wye system (now here is where it gets tricky) transformers can be connected phase to phase and have TWO bushings (mainly for three phase services, rarely if ever for a single phase service) OR be connected phase to ground (ONE primary bushing with the other end of the primary connected to the system neutral.) _*(I will try to get back to this thread with pictures of the transformers here on my property showing both configurations on the same primary system.) *_

The advantage to using a transformer connected phase to ground, especially in the larger sizes, is the use of "graded insulation" on the primary windings. Graded insulation is, simply put, designed such that the insulation of the winding and interlayer wraps becomes thinner the closed you get to the grounded (neutral) end of the primary winding. In large transformers this will result in a significant savings in both weight and materials, which also of course lowers the cost. One drawback to graded insulation though is it has a lesser ability to withstand surges caused by line switching and lightning. 

Big thanks to Harry (aka Black Dog) for the excellent diagrams he posted. :thumbup:


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## RIVETER (Sep 26, 2009)

MXer774 said:


> The cans my shop provides me is of the two primary bushing. H1 being the primary input. H2 gets bonded to the grounded line and the center tap on the secondary bushings. I know of no return back to the station or yard. Or was that not even close to what you were asking. If not then I apologize in advance.


I'm thinking that you are right. I have never done line work and can't see from the ground the hookups. The ground wire that the other end hooks to IS going back to the sub. Is that the way you see it. There has to be a reference to the feeding transformer.


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## Meadow (Jan 14, 2011)

RIVETER said:


> I'm thinking that you are right. I have never done line work and can't see from the ground the hookups. The ground wire that the other end hooks to IS going back to the sub. Is that the way you see it. There has to be a reference to the feeding transformer.


Generally pole pigs come in two bushing types: singe bushing and double bushing. Double bushing has secondary lead insulated from the tank and come with a ground lug for the can. Single bushing units have on of the HV leads connected to the can. There is strap from the can to the LV neutral bushing in addition to the ground lug. That way HV neutral current has two routes to the MGN. 5kv and under pigs can only be sold as double bushing but never understood it. 

Single bushing pigs are cheaper and come easily in "completely self protected". Double hanger version are also available with single bushing designs. 

As for using what is really a ground wire as a current carrying conductor its a practice only common to utilities. All other industries like private MV and train catenary systems tend to avoid the practice (minus DC rail ground return which is beyond the scope of AC transformer) California forbids it as well.


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## circuitman1 (Mar 14, 2013)

*transformers*

hey riveter, the ground ends back at the sub. the phase conductors or hot come from auto transformers in some subs, & the neutral is grounded at the sub on the metal frame work.some power companies don't use regulators. there built into the main tranny. REA uses seperate regulators, these are true auto transformers.some REA's use single bushings for three phase & some two bushing primaries. they just isolate the ground.SCE&G always uses two bushing transformers for both single & three phase setup's. guess this way they have too stock both types.also have seen hi voltage lines with no neutral serving single phase loads. don't quite know how they did that, those systems have been upgraded with a neutral.


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## RIVETER (Sep 26, 2009)

Referring to post #22, Meadow; If a sub is sending...say 7200volts down the line to the first transformer for servicing a home, then THAT return path for the primary of the home transformer has to be going back to the supplying transformer and therefore it is a current carrier even if it is grounded. Am I wrong? The reason I am even venturing into this line of questions is that a group of people I am in discussion with think that the current of the primary just goes into the dirt and I have not had enough beer to believe that.


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## Meadow (Jan 14, 2011)

RIVETER said:


> Referring to post #22, Meadow; If a sub is sending...say 7200volts down the line to the first transformer for servicing a home, then THAT return path for the primary of the home transformer has to be going back to the supplying transformer and therefore it is a current carrier even if it is grounded. Am I wrong? The reason I am even venturing into this line of questions is that a group of people I am in discussion with think that the current of the primary just goes into the dirt and I have not had enough beer to believe that.



Current divides up and takes multiple paths back to the substation transformer. Generally half the current ends up on the MGN the other half tends to be municipal water lines, TELCO shields and even soil. Having 100% of it go to the soil would be an NESC violation.


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## RIVETER (Sep 26, 2009)

meadow said:


> Current divides up and takes multiple paths back to the substation transformer. Generally half the current ends up on the MGN the other half tends to be municipal water lines, TELCO shields and even soil. Having 100% of it go to the soil would be an NESC violation.


If the homes have pvc water then all current should go back on the ground...correct. Dirt is not a good, reliable conductor. AND, is 7200 volts the typical for a residential "pig", as you said?


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## Meadow (Jan 14, 2011)

RIVETER said:


> If the homes have pvc water then all current should go back on the ground...correct. Dirt is not a good, reliable conductor.


Well, when you have thousands of ground rods, UFERs and the like some current does end up going through the ground, in some cases up to 40%.


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## Meadow (Jan 14, 2011)

This PDF explains it to some degree:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.ci.punta-gorda.fl.us%2FAgendaPublic%2FAttachmentViewer.aspx%3FAttachmentID%3D8905%26ItemID%3D6358&ei=ZzkKVfzJKYKwogStgYG4DQ&usg=AFQjCNEymZrpKDxnE0yQvEat5Uerzdmg_Q&bvm=bv.88528373,d.cGU


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## RIVETER (Sep 26, 2009)

meadow said:


> Well, when you have thousands of ground rods, UFERs and the like some current does end up going through the ground, in some cases up to 40%.


That is the part I am trying to come to grips with. You are saying that even if a ground wire were not physically leaving the sub and going down the line to the residence, one wire to the primary would work just fine. Is that right? If so, there would be so many areas that could have a difference of potential in the soil that a farmer's cow could die.


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## Meadow (Jan 14, 2011)

RIVETER said:


> That is the part I am trying to come to grips with. You are saying that even if a ground wire were not physically leaving the sub and going down the line to the residence, one wire to the primary would work just fine. Is that right? If so, there would be so many areas that could have a difference of potential in the soil that a farmer's cow could die.


A single ground rod would be a very bad idea and wouldn't work, however when you combine thousands of high resistance grounds that makes one lower resistance. Varies from place to place but it can become low enough to allow substantial ground current. 

If a home had a metal waterline you could get away with one wire since waterlines are an excellent conductor all by themselves. 

When current flows across earth it creates voltage gradients. The phenomenon is complex, but its really no different that dropping a toaster in a swimming pool or even any conductor carrying current. The resistance creates a voltage drop which in turn creates an elevated potential across 2 points. This event has been known to harm dairy cattle and case pools to shock people.

If you Google "stray voltage lawsuits" the problem is common.


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## RIVETER (Sep 26, 2009)

meadow said:


> A single ground rod would be a very bad idea and wouldn't work, however when you combine thousands of high resistance grounds that makes one lower resistance. Varies from place to place but it can become low enough to allow substantial ground current.
> 
> If a home had a metal waterline you could get away with one wire since waterlines are an excellent conductor all by themselves.
> 
> ...


Well, that'll teach 'em to swim with toasters. I'll have to re-visit this some more but I appreciate the information. I am concerned that I know so much and that most of the guys I know...know less.:thumbsup:


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## Jhellwig (Jun 18, 2014)

RIVETER said:


> That is the part I am trying to come to grips with. You are saying that even if a ground wire were not physically leaving the sub and going down the line to the residence, one wire to the primary would work just fine. Is that right? If so, there would be so many areas that could have a difference of potential in the soil that a farmer's cow could die.


Yes that is correct.

When I worked for a poco it was common practice when replacing poles with dead ends on the grounded conductor we would simply unhook the tie and drop the two ends off the pole. Everything would still work because ever third pole has a groundrod along with every pole that has a surge arrestor or transformer. The linemen did not puck the grounded wire back up without having high voltage gloves on though. We always walked out away from the wire when it was on the ground. You never stepped on it.


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## Meadow (Jan 14, 2011)

RIVETER said:


> If the homes have pvc water then all current should go back on the ground...correct. Dirt is not a good, reliable conductor. AND, is 7200 volts the typical for a residential "pig", as you said?


Most current will flow back via the MGN with only a very small amount going down any single ground rod.


Dirt is not a good conductor, and certainly isn't reliable, however when you have multiple ground rods the combined resistance starts going down. The highest resistance is actually around the ground rod itself. As you move away from the ground rod soil resistance begins dropping in magnitude because each shell has more surface area and progressively there own. But in any case any single ground rod by itself, heck even a dozen ground rods suck as a good conductor even at high voltage. Actually, if you took 7,200 volts to a single ground rod the water around it would boil in addition to extremely dangerous voltage gradients.



Pigs vary between 2400 volts to 19,920 across most utilities. 7,200, 7,900, 13,200 and 14,400 are the most common with 12,000 and 16,000 being the most common in California. In Europe its generally 11,000 and 22,000.


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## RIVETER (Sep 26, 2009)

Jhellwig said:


> Yes that is correct.
> 
> When I worked for a poco it was common practice when replacing poles with dead ends on the grounded conductor we would simply unhook the tie and drop the two ends off the pole. Everything would still work because ever third pole has a groundrod along with every pole that has a surge arrestor or transformer. The linemen did not puck the grounded wire back up without having high voltage gloves on though. We always walked out away from the wire when it was on the ground. You never stepped on it.


Now to me that sounds crazy. In all of this discussion I am not saying that it won't work. I am saying...thinking that it should not be done on purpose. Induction depends on current flow, and that flow has to have a dependable path back to the source of the voltage whether it is the secondary of a transformer outside of the home or the switch yard. And, I am speaking of the 7200 volt single phase feed to the primary.


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## Meadow (Jan 14, 2011)

To answer your original question better, if a brake took place on an MGN if there were enough ground rods the system would continue to work like before.


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## Meadow (Jan 14, 2011)

RIVETER said:


> Now to me that sounds crazy. In all of this discussion I am not saying that it won't work. I am saying...thinking that it should not be done on purpose. Induction depends on current flow, and that flow has to have a dependable path back to the source of the voltage whether it is the secondary of a transformer outside of the home or the switch yard. And, I am speaking of the 7200 volt single phase feed to the primary.


I think it is crazy if several ground rods were truly involved, but if you had hundreds and soil conditions were right its not crazy at all. Toss in Telco shields and its possible even with only 3 ground rods.


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## RIVETER (Sep 26, 2009)

meadow said:


> To answer your original question better, if a brake took place on an MGN if there were enough ground rods the system would continue to work like before.


You obviously know more about this stuff than I do. I am a inside wire man. However, it is a weird concept for me to think that a utility would plan on the earth as a normal conductor. If that is the case I suppose that they know that is why so much power is wasted to "PUSH" it to the user. Weird concept; I'll have to give it more thought. Thanks.


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## Meadow (Jan 14, 2011)

RIVETER said:


> You obviously know more about this stuff than I do. I am a inside wire man. However, it is a weird concept for me to think that a utility would plan on the earth as a normal conductor. If that is the case I suppose that they know that is why so much power is wasted to "PUSH" it to the user. Weird concept; I'll have to give it more thought. Thanks.




Utilities employ this concept not because earth was ever intended to be used as a conductor or because it is a good idea, but rather as cost a effective way in to increase distribution system capacity at little cost decades ago.

Ironically nearly all POCO systems started out as 3 wire ungrounded delta running at 2,400 and 4,800 volts. Back then keeping current off phone lines was essential. 

As load growth took place POCOs needed more capacity and discovered that if a grounded neutral was added (already present in areas with extensive LV runs) the system voltage could be increased to 4160 and 8,300 volts while re-using the same pigs, arrestors and cutouts. Having a redundantly grounded neutral also helped with lightning protection.


Latter on POCOs figured the same practice could be applied to sub-transmission lines to save cost, again. Most sub-transmission lines ran at 12, 23 and 34.5kv (formerly 11, 22 & 33kv) feeding local substations that put out 2,400/4160 and 4,800/8300 volts for local distribution. A MGN was added with single bushing pigs employed at 1.73 times reduced voltage. This allowed existing infrastructure to be re-used while bypassing intermediate substations. 7,200, 13,200 and 19,900 pigs came about in this fashion because they are exactly the phase to neutral voltage of old sub-transmission lines and now distribution lines. 



Because the practice worked out so well it continued to be employed and still is up to the present day.

However, that's not to say issues aren't cropping up as loads increase and antiquated systems fall apart. The magnetic fields produced aren't re-assuring either. 

I would not blame undersized neutrals for all the energy loss. Granted they play a role but a lot of it is a severely dated and undersized infrastructure. POCOs are the only electrical industry on earth that will stop at nothing to save a penny. Never use POCO systems as model of what a good electrical system ought to be like.


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## Meadow (Jan 14, 2011)

Transformer voltages:

http://www.cooperindustries.com/con...urces/library/201_1phTransformers/R201902.PDF


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## KDC (Oct 19, 2012)

RIVETER said:


> You obviously know more about this stuff than I do. I am a inside wire man. However, it is a weird concept for me to think that a utility would plan on the earth as a normal conductor. If that is the case I suppose that they know that is why so much power is wasted to "PUSH" it to the user. Weird concept; I'll have to give it more thought. Thanks.



Utility I work for used to do it fairly often, there's miles of poles out there with just one 7200 hot. Nothing else. 

In fact, our big HVDC link is set up so that if we had to, we could use 1 conductor with a ground return for 250 KV DC. Lots of problems with doing so, but in an emergency, it could be done.


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## RIVETER (Sep 26, 2009)

meadow said:


> Utilities employ this concept not because earth was ever intended to be used as a conductor or because it is a good idea, but rather as cost a effective way in to increase distribution system capacity at little cost decades ago.
> 
> Ironically nearly all POCO systems started out as 3 wire ungrounded delta running at 2,400 and 4,800 volts. Back then keeping current off phone lines was essential.
> 
> ...


Okay, I'll accept all that. So now what about a stray current from the transformer that is trying to make its way back to its source and the best path it can find happens to be through a pond with children swimming in it?


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## Meadow (Jan 14, 2011)

RIVETER said:


> Okay, I'll accept all that. So now what about a stray current from the transformer that is trying to make its way back to its source and the best path it can find happens to be through a pond with children swimming in it?


Equal potential bonding in pools helps as well as diary farm stalls... But lawsuits still happen.


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## Jhellwig (Jun 18, 2014)

RIVETER said:


> Okay, I'll accept all that. So now what about a stray current from the transformer that is trying to make its way back to its source and the best path it can find happens to be through a pond with children swimming in it?


Due to there being almost an infinite number of return paths there is a a very little potential at any given point and that decreases the further away you get from the two point for which the current is flowing.


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## Meadow (Jan 14, 2011)

Jhellwig said:


> Due to there being almost an infinite number of return paths there is a a very little potential at any given point and that decreases the further away you get from the two point for which the current is flowing.


But keep in mind it doesn't stop voltage gradients, especially as the earth gets dry. 

This post isn't mine, nor do I have any idea how accurate but may shed light on the subject:



http://cosmoquest.org/forum/showthread.php?54656-Australian-electricity





> Way in the past, they tried earth return for local distribution networks (kV class). It didn't work out too good, and was very dangerous, putting stray voltages all over the place, caused currents in other wiring systems like the telephone lines, as well any conductors around it could find.
> 
> The dirt just doesn't like 60Hz. It's inductance dominating, IIRC. Take a single wire system, and assume you've got a good low resistance grounding electrode. Rather than spreading out, the current tends to flow in a small zone of soil as close as possible to the hot wire above, and makes the effective resistance very high. Zig zag the wire around some path, and the return current in the soil zigs right under it. That causes large voltage gradients from point A to point B over the soil, which is why any "foreign" wiring or other conductive paths nearby can suddenly find themselves carrying lots of current.
> 
> ...


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## RIVETER (Sep 26, 2009)

This afternoon I was standing at the base of a utility pole with a single phase residential transformer on it. With me was an electrical engineer and a lineman. Knowing that for any current to flow ANYWHERE, there has to be a difference of potential. So, the feed to the transformer was supposedly, 4160 volts. The other side of the primary was attached to the shell of the transformer and then to the wire stapled to the pole and then down into the ground... My thoughts was that in order to have that DIFFERENCE OF POTENTIAL the feed to this transformer winding has to find a way to another phase of the same 4160 volt source. Am I wrong? The others did not know.


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## Meadow (Jan 14, 2011)

RIVETER said:


> This afternoon I was standing at the base of a utility pole with a single phase residential transformer on it. With me was an electrical engineer and a lineman. Knowing that for any current to flow ANYWHERE, there has to be a difference of potential


. 

Correct.




> So, the feed to the transformer was supposedly, 4160 volts. The other side of the primary was attached to the shell of the transformer


 Typical for single bushing units.



> and then to the wire stapled to the pole and then down into the ground...


 That would be a code violation. The shell is connected to the MGN, and from the MGN you have the wire running to the ground rod. 





> My thoughts was that in order to have that DIFFERENCE OF POTENTIAL the feed to this transformer winding has to find a way to another phase of the same 4160 volt source. Am I wrong? The others did not know.


 The neutral has impedance back to the substation, so current will be shunted over to the ground rod. 


Now, does current go up and down as you move along the MGN and earth? You bet! If the transformer next to it is on another phase that will either add or deduct current to the ground/neutral. Exact same thing with a MWBC, current will be different across your full boat as you hit devices, sometimes much higher than at the panel.

Take this example: A line 2 miles from a substation heading up to a pole with a pig connected phase A to MGN at 100amps, 150 feet away another pig B to MGN also at 100amps and yet another pig 300 feet away from the first one connect C to MGN, also drawing 100amps. The MGN between pigs A & B will measure 100amps, while the MGN between pigs B & C will also measure 100amp. In reality the current will be less through the MGN because some will divert to the ground, TELCO shields and the customer's water bonds/ UFERs. So we might see 70amps on the MGN with 20amps on the water line in the street, 8 amps on the TECLO shields and 2 amps going across soil from ground rods. However, heading back toward the substation, what will the current on the MGN be? 100 amps? Nope. Zero! In fact you could even go as far and removing the neutral and nothing would happen to the load or operation of the transformers. Current on metal water lines, TELCO shields ect will also be zero, even tough 100amps is going between the pigs. 


Of course this is assuming perfectly balanced load. If for what ever reason pig C's (or A or B, but not all at once) load changed from 100 to 105 amps then, then 5 amps would appear between pig A and the substation. If the loads are none linear like VFDs, current would also appear between the pigs and the substation. How much depends on harmonics and the level of imbalance between the pigs which is dependent on the customer's load. 

Toss in more pigs and real world loads and the current will vary considerably both in the MGN and thus soil/pipes/TELCO shields. 


An interesting irony is that on a hot summer's day residential sub-divisions will often have much higher ground current than the 3 phase lines on the street because those in subdivisions are single phase. No pigs exist on opposite phases to cancel some of that current out.


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## don_resqcapt19 (Jul 18, 2010)

RIVETER said:


> This afternoon I was standing at the base of a utility pole with a single phase residential transformer on it. With me was an electrical engineer and a lineman. Knowing that for any current to flow ANYWHERE, there has to be a difference of potential. So, the feed to the transformer was supposedly, 4160 volts. The other side of the primary was attached to the shell of the transformer and then to the wire stapled to the pole and then down into the ground... My thoughts was that in order to have that DIFFERENCE OF POTENTIAL the feed to this transformer winding has to find a way to another phase of the same 4160 volt source. Am I wrong? The others did not know.


The shell of the transformer is connected to the secondary neutral. The secondary neutral runs from pole to pole and at some point is connected to the primary neutral.


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## Meadow (Jan 14, 2011)

don_resqcapt19 said:


> The shell of the transformer is connected to the secondary neutral. The secondary neutral runs from pole to pole and at some point is connected to the primary neutral.


Often the secondary and primary neutral are the same conductor.


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## circuitman1 (Mar 14, 2013)

don_resqcapt19 said:


> The shell of the transformer is connected to the secondary neutral. The secondary neutral runs from pole to pole and at some point is connected to the primary neutral.


then eventually ends back at the substation.just follow one close to a sub.:thumbup:


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> Often the secondary and primary neutral are the same conductor.


Almost always the same conductor around here.


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## Meadow (Jan 14, 2011)

don_resqcapt19 said:


> Almost always the same conductor around here.


 
Triplex, right?


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> Triplex, right?


Triplex to the buildings...almost all of the pole to pole wiring is single conductor except for some of the primary that is Hendrix cable.


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## Meadow (Jan 14, 2011)

don_resqcapt19 said:


> Triplex to the buildings...almost all of the pole to pole wiring is single conductor except for some of the primary that is Hendrix cable.


Spacer cable when you mean Hendrix cable?

Spacer cable typically has a dedicated LV neutral since the messenger cant be used as one, but regular lines are like you say, single conductor LV/MV noodle or triplex LV "buss".


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> Spacer cable when you mean Hendrix cable?
> 
> Spacer cable typically has a dedicated LV neutral since the messenger cant be used as one, but regular lines are like you say, single conductor LV/MV noodle or triplex LV "buss".


The utility calls it *Hendrix*  around here...I am sure that is a brand name. On the run in front of my house, the bare messenger is connected to the ground rods at each pole, probably for lighting protection and to avoid inductive voltage rise on the messenger. The grounded conductor is a common conductor for both the primary and secondary circuits.


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## Meadow (Jan 14, 2011)

don_resqcapt19 said:


> The utility calls it *Hendrix* around here...I am sure that is a brand name. On the run in front of my house, the bare messenger is connected to the ground rods at each pole, probably for lighting protection and to avoid inductive voltage rise on the messenger. The grounded conductor is a common conductor for both the primary and secondary circuits.


In spacer cable the messenger is usually the MGN itself, at least for the MV. Its earthed both for lightning and NESC requirements pertaining to MGNs.


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## RIVETER (Sep 26, 2009)

don_resqcapt19 said:


> The shell of the transformer is connected to the secondary neutral. The secondary neutral runs from pole to pole and at some point is connected to the primary neutral.


I agree but at what point does one phase of 4160 get to another phase of 4160 for the current to flow. When generating voltage one phase...or the other is not searching for GROUND...just because.


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## Meadow (Jan 14, 2011)

RIVETER said:


> Okay, I'll accept all that. So now what about a stray current from the transformer that is trying to make its way back to its source and the best path it can find happens to be through a pond with children swimming in it?


The current will take all paths, more on good ones less on bad ones, but kirchoffs voltage law still holds. When current passes through and resistance (like soil) voltage drop takes place. Voltage drop is in essence current trying to find more paths back, but it cant until something else is introduced, and when introduced will flow through that. This might be people, animals across the earth anything. I can drive 2 ground rods 6 feet apart anywhere around an MGN system and measure a 60hz voltage. 

If the path is through a lake, voltage gradients will form as a result of the voltage drop. If enough current is being pushed through the earth people swimming will start to feel it. Its actually one of the reasons why we bond pools, because MGNs on average have about 1 volt relative to earth. 1 volt is not much, but in water you do feel it.


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## RIVETER (Sep 26, 2009)

Okay, But as I suggested in post #56 current only flows from a source of voltage out to "SOMEWHERE", AND THEN BACK TO THE SAME SOURCE OF VOLTAGE. How then does 4160 to a transformer that is then connected to earth do the job?


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## Meadow (Jan 14, 2011)

RIVETER said:


> Okay, But as I suggested in post #56 current only flows from a source of voltage out to "SOMEWHERE", AND THEN BACK TO THE SAME SOURCE OF VOLTAGE. How then does 4160 to a transformer that is then connected to earth do the job?


The transformer is not connected directly to earth, its connected to an MGN which is earthed repeatedly. The earth is just a parallel circuit.


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## fargowires (Aug 26, 2010)

Black Dog, you amaze me. As does anyone of the many helpful, quick, argumentative, trollish, knowledgable, funny, wacky, entertaining, guys on here.
When I see a response like those diagrams, followed by encouragement, trolling, whatever, I think:















WHEN DO THESE GUYS WORK? HOW DO THEY MAKE A LIVING?


I am in awe of all you multi-k posters.
Thank you.


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## Meadow (Jan 14, 2011)

Pic didn't come through... unless you intended the space.

Anyway, thanks, and yes this place can be addicting


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## RIVETER (Sep 26, 2009)

meadow said:


> The transformer is not connected directly to earth, its connected to an MGN which is earthed repeatedly. The earth is just a parallel circuit.


BUT, The source phase has to be satisfied by achieving connection to an opposite phase. Earth is just a reference.


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## Meadow (Jan 14, 2011)

RIVETER said:


> BUT, The source phase has to be satisfied by achieving connection to an opposite phase. Earth is just a reference.


But to what degree it achieves to the other phase varies on the load attached to the other phase. Think a MWBC, neutral current can be a lot or a little depending on how well balanced the load is.


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## RIVETER (Sep 26, 2009)

Let me give a scenario that I don't particularly agree with but it is mine. Three phase circuit 4160 running along a road and A phase goes to the left into a subdivision and phase B goes right into a subdivision. The primaries on the end of the winding goes into the dirt. All is good. What do you say?


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## Meadow (Jan 14, 2011)

RIVETER said:


> Let me give a scenario that I don't particularly agree with but it is mine. Three phase circuit 4160 running along a road and A phase goes to the left into a subdivision and phase B goes right into a subdivision. The primaries on the end of the winding goes into the dirt. All is good. What do you say?


Not to code  

In all reality current will flow across the earth and in various (gradually over a distance) places cancel with the remainder going back to the sub assuming everything is earth return. But now that I think about it that's an excellent question.


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## Meadow (Jan 14, 2011)

you might like this, a 3 phase current calculator:

http://forums.mikeholt.com/showthread.php?t=167171&page=4&p=1624520#post1624520


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## RIVETER (Sep 26, 2009)

meadow said:


> Not to code
> 
> In all reality current will flow across the earth and in various (gradually over a distance) places cancel with the remainder going back to the sub assuming everything is earth return. But now that I think about it that's an excellent question.


It IS an excellent question...Thanks. My contention is that Phase voltage is not inherently trying to go to ground. It is trying to get to a point of DIFFERENCE of potential. Generated voltage is not natural and is unlike lightning.


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## Meadow (Jan 14, 2011)

RIVETER said:


> It IS an excellent question...Thanks. My contention is that Phase voltage is not inherently trying to go to ground. It is trying to get to a point of DIFFERENCE of potential. Generated voltage is not natural and is unlike lightning.


Correct. Its not seeking ground, but rather the differences in potential. 

Picture it like this:

The neutral may be close to potential relative to earth, but if you went in the substation and cut the neutral between the ground mat and X0 bushing the voltage between the two would be thousands of volts, even up to the maximum phase to neutral voltage. The MGN has resistance, so a voltage drop occurs arcos the MGN and shunts some current to earth. Transformers rotating across the phases will deduct or add current to the MGN.


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## don_resqcapt19 (Jul 18, 2010)

RIVETER said:


> I agree but at what point does one phase of 4160 get to another phase of 4160 for the current to flow. When generating voltage one phase...or the other is not searching for GROUND...just because.


If the 4160 is line to line there will be two ungrounded conductors and two primary bushings on the transformer. A transformer that has only one primary bushing is always connected line to neutral.

If the primary of the transformer is really 4160 and one side of the primary is connected to ground it could be a 7200y/4160 volt system. 

It also could be a 2400 volt primary which is line to neutral voltage on a 4160 volt wye system.


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## Meadow (Jan 14, 2011)

I took some pics, I think they will help you picture this. Check out the last one:


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## Meadow (Jan 14, 2011)

These are typical single bushing transformers meant for MGN systems. There is only one HV bushing with the other side of the HV winding bonded to the can internally.


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## Meadow (Jan 14, 2011)

These are double bushing pigs. Notice the neutral to can bond strap is not present. Its up to the POCO where to connect the can and LV noodle. Where tags say for example 7,200/12,470Y; this means that the HV coil is 7,200 volts. Thus, such a pig may be connected phase to phase on a 4160/7200Y or 7200 ungrounded delta system or phase to neutral on a 7200/12470Y system.


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## Meadow (Jan 14, 2011)

.....


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## MTW (Aug 28, 2013)

meadow said:


> I took some pics, I think they will help you picture this. Check out the last one:


That's CL&P utility practice right there. :whistling2::laughing:


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## Meadow (Jan 14, 2011)

MTW said:


> That's CL&P utility practice right there. :whistling2::laughing:


You mean Evercarp oops I mean Eversource? :laughing:


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## RIVETER (Sep 26, 2009)

Those are some great pics. So you are saying that in the 4160 volt wye system the poco is relying on the return current to the substation from the primary of the transformer to take a "hap hazard" way back to the source transformer via anywhere it can???


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## Meadow (Jan 14, 2011)

RIVETER said:


> Those are some great pics. So you are saying that in the 4160 volt wye system the poco is relying on the return current to the substation from the primary of the transformer to take a "hap hazard" way back to the source transformer via anywhere it can???




In any MGN system be 4.16kv or 34.5kv, the answer is yes.  I know, goes against everything electricians are taught, but its big business saving a few bucks. 

California on the other hand has rules forbidding this exact practice.


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## chicken steve (Mar 22, 2011)

Being taught _'earth'_ sucks up lightning yet does _not _conduct electricity is cognitive dissonance at it's finest Meadow

Iirc, even lightning is seeking potential , but i digress....

What would happen in Riv's displaced phase(s) scenario where the poco noodle 'floated' or 'isolated' (not sure which term fits?) from the secondary of the aforementioned piglets ? 

~CS~


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## Meadow (Jan 14, 2011)

chicken steve said:


> Being taught _'earth'_ sucks up lightning yet does _not _conduct electricity is cognitive dissonance at it's finest Meadow
> 
> Iirc, even lightning is seeking potential , but i digress....
> 
> ...


 
The strap is a back up to the tank bond. The can is the second lead of the HV, so it needs that MGN.

If the MGN breaks, copper water lines take over.


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## RIVETER (Sep 26, 2009)

meadow said:


> Not to code
> 
> In all reality current will flow across the earth and in various (gradually over a distance) places cancel with the remainder going back to the sub assuming everything is earth return. But now that I think about it that's an excellent question.


Yeah, and to top it off I was visiting my mother in law at the hospital and met a very successful electrical engineer and asked him what he thought. IT FLOORED ME. He said that virtually ALL electricity is trying to get to earth. I said that it SHOULD be trying to get back to its source. He then said, well, even in cars...if they did not have rubber tires the current would go back to the earth and I definitely am not kidding... he said that. What are they teaching them these days?


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## papaotis (Jun 8, 2013)

seriously?:001_huh:


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## Meadow (Jan 14, 2011)

RIVETER said:


> Yeah, and to top it off I was visiting my mother in law at the hospital and met a very successful electrical engineer and asked him what he thought. IT FLOORED ME. He said that virtually ALL electricity is trying to get to earth. I said that it SHOULD be trying to get back to its source. He then said, well, even in cars...if they did not have rubber tires the current would go back to the earth and I definitely am not kidding... he said that. What are they teaching them these days?





I think they teach this stuff to hide some inconvenient truths. Either that those teaching just don't know electrical theory. 

I think I am finally starting to understand why I become persona non grata in any education setting... :no:


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## RIVETER (Sep 26, 2009)

papaotis said:


> seriously?:001_huh:


I am as serious as cancer. I am not making this up..


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## Meadow (Jan 14, 2011)

RIVETER said:


> I am as serious as cancer. I am not making this up..



Are you sure you dint accidentally stumble into a DIY chatforum?


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## papaotis (Jun 8, 2013)

what if we took the tires off the rims, parked it in a puddle and disconnected the neg.?


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## RIVETER (Sep 26, 2009)

papaotis said:


> what if we took the tires off the rims, parked it in a puddle and disconnected the neg.?


I see that you understand my dilemma. I assure you that I really know how this stuff works. It astonishes me how so many seem to not have a clue but they still make money.


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## papaotis (Jun 8, 2013)

invite him to your booth at the picnic:laughing:


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## RIVETER (Sep 26, 2009)

papaotis said:


> invite him to your booth at the picnic:laughing:


I actually did invite him and explained my involvement. He got kind of un-nerved and said that he would not stand for that...I said that he wouldn't have to..:whistling2:


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## Meadow (Jan 14, 2011)

RIVETER said:


> I actually did invite him and explained my involvement. He got kind of un-nerved and said that he would not stand for that...I said that he wouldn't have to..:whistling2:


No are so blind as those who refuse to see, none so dead as those who refuse to hear.


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## RIVETER (Sep 26, 2009)

meadow said:


> No are so blind as those who refuse to see, none so dead as those who refuse to hear.


WOW!!!! That is deep. I once told that to a guy at the booth.


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## papaotis (Jun 8, 2013)

and did he grunt or oooh?


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## RIVETER (Sep 26, 2009)

papaotis said:


> and did he grunt or oooh?


I don't remember.
It was a PROFESSIONAL moment.


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## RIVETER (Sep 26, 2009)

In order to get this THREAD back on track I have to ask ALL of you guys. Does it make sense to take a hot wire into a subdivision with no return to the source and expect that the return current will, somehow, find it's way back to the source transformer. AND, PLEASE, just the smart guys here respond.:thumbsup:


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## papaotis (Jun 8, 2013)

which makes another question. if the poco grounds the nuetral at every pole, does it ever get back to the source?:001_huh:


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## Meadow (Jan 14, 2011)

RIVETER said:


> WOW!!!! That is deep. I once told that to a guy at the booth.



:laughing: And thanks!


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## metalpats (Apr 11, 2011)

RIVETER said:


> In order to get this THREAD back on track I have to ask ALL of you guys. Does it make sense to take a hot wire into a subdivision with no return to the source and expect that the return current will, somehow, find it's way back to the source transformer. AND, PLEASE, just the smart guys here respond.:thumbsup:


yes and it is called 

Single
Wire
Earth
Return


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## JW Splicer (Mar 15, 2014)

Why is everyone so bent on SWER here? It is very very rarely used... But it's out there and it works. Most (like 99%) of utility installs want a neutral from the sub out to the load, mainly for primary wye, and secondaries. RIV, we carry a neutral out from the sub for our underground delta. It attaches to a neutral bus at every vault, which in turn has at least 2 ground rods and one 250 kcmil ufer. It's grounded so often so that it makes an equipotential zone which reduces hazards to employees, public, and equipment during a fault condition.


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> In any MGN system be 4.16kv or 34.5kv, the answer is yes.  I know, goes against everything electricians are taught, but its big business saving a few bucks.
> 
> California on the other hand has rules forbidding this exact practice.


While the path maybe be "hap-hazzard", it is in almost all cases, in the US, a physical path, often via the secondary grounded conductor which has a connection to a primary grounded conductor back to the source.


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## don_resqcapt19 (Jul 18, 2010)

RIVETER said:


> In order to get this THREAD back on track I have to ask ALL of you guys. Does it make sense to take a hot wire into a subdivision with no return to the source and expect that the return current will, somehow, find it's way back to the source transformer. AND, PLEASE, just the smart guys here respond.:thumbsup:


That is extremely rare in the US, and I would bet that there are no subdivisions fed using SWER in the US. There are some limited applications in very rural areas, but not common here.


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## cuba_pete (Dec 8, 2011)

RIVETER said:


> He said that virtually ALL electricity is trying to get to earth. I said that it SHOULD be trying to get back to its source. He then said, well, even in cars...if they did not have rubber tires the current would go back to the earth


Wow, hope he doesn't go around waving 9v batteries all willy nilly...what with all their high current capacity and ungrounded nature.

Don't touch the tops of those d-cells, either.


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## Meadow (Jan 14, 2011)

JW Splicer said:


> Why is everyone so bent on SWER here? It is very very rarely used... But it's out there and it works. Most (like 99%) of utility installs want a neutral from the sub out to the load, mainly for primary wye, and secondaries. RIV, we carry a neutral out from the sub for our underground delta. It attaches to a neutral bus at every vault, which in turn has at least 2 ground rods and one 250 kcmil ufer. It's grounded so often so that it makes an equipotential zone which reduces hazards to employees, public, and equipment during a fault condition.



And helps to trigger the ground fault alarm as well. What voltage is your ungrounded delta system?


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## MDShunk (Jan 7, 2007)

To the system MGN. multi grounded neutral.


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## JW Splicer (Mar 15, 2014)

We've got multiple 13.8 kv and a 26kv delta network, the 26 has 5 feeders on it. We also have a 26KV wye network fed from a few overhead feeders.


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## Meadow (Jan 14, 2011)

JW Splicer said:


> We've got multiple 13.8 kv and a 26kv delta network, the 26 has 5 feeders on it. We also have a 26KV wye network fed from a few overhead feeders.


Why ungrounded? Hold over?

And oh, lightening bolts aren't shooting out of the wires on those systems, right? :laughing::laughing:


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## JW Splicer (Mar 15, 2014)

Well the 13.8 is delta because it comes off of the tertiary windings. Our giant transformers at our receiving stations are auto transformers. Some are 240KV input with output at 115KV to other subs, as well as 26KV for all the overhead distribution, and they have a tertiary in delta. Sometimes tertiary windings don't carry load and they're only function is reduction of harmonics. We pulled load off of ours at 13.8kv to feed the network bus sections. That's why they're in delta. The sub has a zigzag off the 13.8 delta for ground reference. The 26KV network is a wye system up to a buck boost and then delta after that. Nobody seems to know why haha.


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## Meadow (Jan 14, 2011)

There are voltage regulators on the 13.8kv after the tertiaries right? And how is the zig-zag earthed?


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## JW Splicer (Mar 15, 2014)

No voltage regulators, straight to the bus. The zig zag is in parallel with the windings and bus. earthed through a resistor at the center point. 200A trips the relay.


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## Meadow (Jan 14, 2011)

JW Splicer said:


> No voltage regulators, straight to the bus. The zig zag is in parallel with the windings and bus. earthed through a resistor at the center point. 200A trips the relay.



Not ungrounded delta then :jester: You have chock reactor before feeding into he buss right?

Does the 13.8kv feed step down distribution sub or directly to customers?

I ask because the voltage regulation of tertiary windings tends to be poor, and the impedance generally tends to be very low supplying fault currents well over 12.5ka.


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## JW Splicer (Mar 15, 2014)

I could be wrong, the substations guys would know way more, but from what I understand, no voltage regulators, 13.8 straight to the network transformers. You're right, technically its a high resistance grounded delta. Best of both worlds!


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## RIVETER (Sep 26, 2009)

meadow said:


> :laughing: And thanks!


I remember...you were AWESOME.


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## Meadow (Jan 14, 2011)

RIVETER said:


> I remember...you were AWESOME.


Huh?:001_huh:


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## RIVETER (Sep 26, 2009)

meadow said:


> :laughing: And thanks!


I WAS trying to be professional and not to give your identity. Now it's out.:thumbsup:


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## RIVETER (Sep 26, 2009)

metalpats said:


> yes and it is called
> 
> Single
> Wire
> ...


Yeah, I've heard. But why, then does everyone wonder where gradients and step potentials come from?


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## Meadow (Jan 14, 2011)

RIVETER said:


> I WAS trying to be professional and not to give your identity. Now it's out.:thumbsup:


Oh, my bad then :laughing:


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## RIVETER (Sep 26, 2009)

After all of this we still don't have an answer.


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## RIVETER (Sep 26, 2009)

meadow said:


> Well, when you have thousands of ground rods, UFERs and the like some current does end up going through the ground, in some cases up to 40%.


Got call yesterday after a storm. Lights burning half brilliance...tv dim...etc. Poco says it was an 
open neutral at the pole. Okay, so, if you guys who say that the return current will find a way back...why didn't it?


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## Meadow (Jan 14, 2011)

RIVETER said:


> Got call yesterday after a storm. Lights burning half brilliance...tv dim...etc. Poco says it was an
> open neutral at the pole. Okay, so, if you guys who say that the return current will find a way back...why didn't it?



It did, by a few amps at most, not enough to allow all the current through.


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## circuitman1 (Mar 14, 2013)

RIVETER said:


> Got call yesterday after a storm. Lights burning half brilliance...tv dim...etc. Poco says it was an
> open neutral at the pole. Okay, so, if you guys who say that the return current will find a way back...why didn't it?


when this happened to a friend of mine the effect was quite the opposite the lights looked like spot lights, burnt up his tv, microwave , and a few other appliances.power company paid for them.:001_huh::001_huh:


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## RIVETER (Sep 26, 2009)

meadow said:


> It did, by a few amps at most, not enough to allow all the current through.


that is what I have been saying...not to rely on earth for the return back to the service.


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## papaotis (Jun 8, 2013)

why not?


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## RIVETER (Sep 26, 2009)

papaotis said:


> why not?


Because it is not reliable.


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## papaotis (Jun 8, 2013)

uh, oh !


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## Meadow (Jan 14, 2011)

RIVETER said:


> that is what I have been saying...not to rely on earth for the return back to the service.



Ditto. I dont get why people have grounding to be both a mystery and some type of magical fix all happy ending fairy tail. I get where you are coming from and this exact concept I find myself explaining all the time.

In the US ground rods have nothing to do with 60Hz power, and I mean nothing be it normal operation or clearing a fault. Even with interference they serve no purpose.


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## Meadow (Jan 14, 2011)

RIVETER said:


> Because it is not reliable.



What I tell everyone: how will 30 ohms have less impedance resistance then 0.04 ohms? Gets them every time :laughing:


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## RIVETER (Sep 26, 2009)

I think you just got ME.


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## Meadow (Jan 14, 2011)

RIVETER said:


> I think you just got ME.



Drive a ground rod :laughing::jester:


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## billn (Aug 31, 2011)

Keep in mind about that earth return path. Since there is resistance, there is a voltage drop across it - voltage that is lost elsewhere in the circuit. That voltage drop also varies with the current flowing through the earth return. In ancient times, it was not uncommon in rural areas to have just a single hot transmission line - relying on the earth path as the only return. But then, the average ranch/farm had only a few electric lights and a tube radio. If affluent, they might have a refrigerator and milking machine as well.


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## RIVETER (Sep 26, 2009)

billn said:


> Keep in mind about that earth return path. Since there is resistance, there is a voltage drop across it - voltage that is lost elsewhere in the circuit. That voltage drop also varies with the current flowing through the earth return. In ancient times, it was not uncommon in rural areas to have just a single hot transmission line - relying on the earth path as the only return. But then, the average ranch/farm had only a few electric lights and a tube radio. If affluent, they might have a refrigerator and milking machine as well.


EARTH RETURN PATH.........wHY...AND TO WHERE?


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## cuba_pete (Dec 8, 2011)

Here we go with the SWER thing again, like its new...


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## pete87 (Oct 22, 2012)

meadow said:


> ...
> 
> In the US ground rods have nothing to do with 60Hz power, and I mean nothing be it normal operation or clearing a fault. Even with interference they serve no purpose.




I always thought that the Ground Rods in the US , were for Lightning .




Pete


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## Meadow (Jan 14, 2011)

pete87 said:


> I always thought that the Ground Rods in the US , were for Lightning .
> 
> 
> 
> ...



They probably are, for the POCO :laughing:


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## RIVETER (Sep 26, 2009)

pete87 said:


> I always thought that the Ground Rods in the US , were for Lightning .
> 
> 
> 
> ...


That is true, and they are only for that purpose.


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## RIVETER (Sep 26, 2009)

I drove to my cabin in south central Kentucky and it is hard to not look at the power distribution lines. In the rural areas there always seems to be a ground as well as the hot feed. I am talking about the ground...rather, the return conductor back to the POCO.


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