Another motor question.

[ajbachhuber]

How quick we are to judge...

Boy, everybody jumped all over poor Hoot in a hurry. Though the phenomenon ol' Hoot mentioned may not have anything to do with the problem at hand, it must not be discounted. Here are a couple of links to Mike Holt Enterprises, a National Electric Code discussion forum amongst other things.

Effects on cattle

This is a partial explanation of "Ground Currents"

An IEEE "Life Fellow" complains that not enough is being done

An explanation of ground currents

Dangers of stray voltage and current

Electrical SHOCK hazard due to stray voltage

Last but not least is the "Stray Voltage Handbook"

Oh yeah, you also need to check out www.strayvoltage.org
Check out the discussion forum with parents of children with birth defects who claim stray voltage effected their children.

See if you can find the recurring theme of rural electrical service...

 

[Eric Nelson]

Dear God, I've heard of some 'hokey' systems, but THAT one takes the cake! And here I thought Hoot had lost his mind...

So, how do you 'plug in' say, a toaster? String one of the leads up the pole to this 'line' and stuff the other lead into the ground? I guess that's why the houses have dirt floors... Real easy to connect to the 'return'...

Let me guess, this is what a standard 'rural' duplex receptacle looks like...
[attachment]
In any case, thanks for enlightening me on this strange wiring practice. You learn something new every day!...

beerchug

-Eric

 

[rsdoran]

Technically there was a time when we did that

Eric there are places in the US where they just ran one line to homes and the Earth ground was the neutral....matter of fact this old house I live in now was once that way...had no 240 at all, was all 120 service. In the 60's my Uncle rewired it for 240vac service...I have to do it all again now. GFCI, Arc suppression etc.

I dunno what HOOT experienced but having dealt with alot of strange electrical problems I believe it may have had to do with the way they wired things.
NOTE: The earth can not be "hot"
NOTE: as stated before there is no such thing as excess "power". If the electrical lines were any in way attached to Earth ground that would cause a tremendous load....pretty much a dead short.

Earth is by far too large to allow any form of electrical charge to be maintained, thats why its is used as a ground. Electricity that goes to ground is neutralized....or should be, at least blow a fuse or trip a breaker.

Simple fact IS that things go wrong...the ground system can become "hot" in many cases. If you investigate tho you will find WHY its HOT and WHY the ground didnt neutralize it, usually wiring issues or bad groumd connections are the problem.

 

[Alan Case]

Eric. In our more remote areas in Australia the high voltage reticulation is done at 11KV on 1 wire. The 11KV to 240V transformer uses the ground for the 11KV return wire. The 240V system uses the normal wiring system, ie 1 active wire, 1 neutral wire and an earth that is bonded to the neutral. This method is not that uncommon here and I am sure you would have similar systems in the states.
I might not have explained it that well to start with. ( I should of explained that I meant the high voltage side of the network) I never meant you stick one end of the toaster in the ground. Regards Alan Case

 

[Terry Woods]

What a Kick in the A$$ this has turned into! It's GREAT!

Ron said...

NOTE: The earth can not be "hot"


To which I say... HOT is a "relative" issue.

Take a 120VAC line... tie two taps onto it.
Connect a 500-ohm resistor to each tap.
Connect the other end of one of those resistors to a ground-rod over here (in damp dirt).
Connect the other end of the other resistor to a ground-rod over there (in dry sand).

Measure the current going through each line to its' ground-rod... there will be a difference. Simply because of this difference, there will be a difference in the potential between the connection points on the two rods.

Measure the voltage between the two rods... there will be a potential difference.

(I know you know this Ron,... this is for the kids!)

If we make a few assumptions...
- the ground-rod in the dirt line is perfect...
- the ground-rod in the sand line is less than perfect (500-ohms)...
- the resistance between Mother Earth(1) and Mother Earth(2) is 0-ohms...
(that's not likely, but let's assume so)
- the resistance between Mother Earth(1)&(2) and the "source ground point" is 0-ohms...

                                       Dirt

                    500-ohms          0-ohms

              +------/\/\/\/---(A)----/\/\/\/--------- Mama Earth(1)

              |

              |

 120VAC-------+

              |                        Sand

              |     500-ohms         500-ohms 

              +------/\/\/\/---(B)----/\/\/\/--------- Mama Earth(2)

.
At the connection points, (A) or (B), one of those rods will be "HOT" relative to the other. That is, of course, the very basis of electrical distribution - "potential difference".

The current in the "dirt line" will be 120/500 = 240 mA
The current in the "sand line" will be 120/1000 = 120 mA

The damp dirt will present a much lower resistance to good ol' Mother Earth than the dry sand. So the resistance in the "sand" line will be much higher, thus resulting in much lower current. The voltage at (B) will be anything but zero... your basic "voltage divider".

If "e" stands for mama earth...
The voltage at (A), that is, Vae(1), is 0-VAC.
The voltage at (B), that is, Vbe(2), is 60-VAC.

The voltage between (A) and (B), that is, Vab, is 60-VAC.

Now, be a sport, play along and take off your shoes...

Place one bare foot by this rod and the other bare foot by that rod... go "MoooOOOOO!" You will indeed feel that warm, fuzzy feeling that we electricians (and cows) have come to know - all too well.

And, if you can't feel it... have your wife (females in general) stand in your place... for whatever reason, she is more inclined to feel it! I'll be damned if I know why! Maybe it's the "relative" amount of "water" in a female body.

I used to work in a shipyard and a railroad car manufacturing plant. We had a lot of female welders. They were always complaining about feeling snake-bit.

If the resistance between Mother Earth(1) and Mother Earth(2) is NOT 0-ohms, then the game is further complicated. Likewise if the resistance between Mother Earth(1)&(2) and the source is NOT 0-ohms, then, again, there are more complications.

If the resistance between Mother Earth(1) and (2) is 0-ohms but the resistance between Mother Earth(1)&(2) and the "source ground point" is NOT 0-ohms, then... the potential difference between (A) and (B) is reduced! AHA! Let's just introduce some resistance between Mother Earth and the "source gound point"!

That might be better for us in the near-term... however, that resistance is using power... and I don't think the generator plant is willing to swallow that cost.

The point is, All Mother Earth Ground Points are NOT created equal! Thus, potential differences!

With respect to the URL's posted by ajbachhuber, I found the one named "Stray Voltage Handbook" to be a very simple, straight-forward explanation of the basic problem. It is well worth the read.

Turning on the "Way Back Machine", I found a couple of really old threads talking about grounding. Interesting stuff. Also, it was nice to be reminded of a lot of old friends that haven't been around for quite a while.


Ooops! I forgot to post the url's

http://www.plcs.net/dcforum/DCForumID4/321.html

http://www.plcs.net/dcforum/DCForumID5/1588.html

There are a bunch of these in the old forum.

 

[Hootnholler]

Hey guys,

Really, didn't mean for this to take such a tangent, had no idea it would be such a hot topic... (no pun intended...)

First, to Ron and Eric, guys, really, I understand what you are trying to say, and I'm not trying to be a jerk, I'm trying to piece it together also. I am by no means an electrical engineer, just a technician in factories. Gimme a control panel, no problem. Put me outside on a pole, um, have no idea. All I know is that we had stray voltage, had to do with the pole wiring and grounds and it was affecting our business. I assumed wrongly that this may be something for Rick to think about, since this pertains to farms, and he mentioned he was working on a farm... Now that I know it's 230 VAC, which I had missed, this cannot be the issue. I didn't even think about it until the post about the 2 motors, one free spinning, becoming a generator... I took a leap of faith with my feeble knowledge, and I was wrong.

To aj, Alan and Terry, what you guys are describing is starting to make sense. What I do remember is the power company coming out and saying that we were within the limits. My father had lost a ton of money, and I finally paid out of my pocket for a private electrician to test for the stray voltage. I had no idea what it was, just that my old man was in trouble. I paid for it, the guy came out and just kept saying 'wow'. We had 4 times the maximum allowed. That much I do remember... I was living in Lansing at the time, so I don't have first hand knowledge of it all. Plus, my old man is by no means an electrician, so I do accept that the information I have is muddy, at best. I do vividly remember coming up from Lansing to help him out, and have a few scars from the kicks and bumps when putting on the milkers. The stray voltage handbook makes a lot of sense, the differing grounds, since I was told that it had to do with the saturation of the soil, the cows urinating and the salt being conductive.

Overall, it went to mediation. Long story, but it ended up being our local vetrenarian as the mediator, but we had no idea that he also worked for the power company. He was not put in an enviable position. He ruled against the power company, he cut his throat with them. If he ruled against us, he cut his vet business with the local farmers. We ended up with a $2000 settlement, after losing over $400,000 on paper that could be proved, but in reality, it was much more. Needless to say, the farm is no longer a dairy farm. I know that this has nothing to do with the thread, just hoping it will make sense why it sticks in my craw so bad... and again, you guys have taught me. I am greatly indebted.

Mr. Densing, I apologize for the weird turn this thread has taken. If I had known that it would turn out this way, I woulda just kept my mouth shut. I love the information that this forum posts, and thought I may have something to add, or a way to repay what I have learned. I do hope that you are able to figure it out for them and also hope that there's no ill will from my ignorance. For me, it was single phase, farm, generator... hm... stray voltage? That was the essence of my post. Now I know that it's a non issue in your problem.

Keep up the great work! I'll just be the student again... lol.

Hoot

 

[Eric Nelson]

Tangents are good!...

I just go an update. They've done nothing. The conveyor is not needed until November and being contractors, they started the job and will come back later.

Looks like the original question is 'on hold', so I don't see any reason not to start a tangent. We probably should have started a new thread, but then it wouldn't be a 'tangent' per se!...

First things first... Hoot, please stop apologizing (at least to ME). I should be the one apologizing to YOU for jumping all over your post. Since I had never heard of such a thing as SWER, I saw you're post as equivalent to stating that "the earth is flat".

Also, thanks Alan for clarifying that SWER is more common on transmission lines (high voltage) rather than a local utility practice. By high voltage, I mean >13.2KV, which I always got a kick out of (no pun intended). That's what the utility companys consider high voltage, but anthing over 600V is pretty darn 'high' in MY opinion...

Terry, great post (as expected). Now I understand how much easier it was to start tangents on the old board. I think the regulars here will be able to follow this tangent, no matter how convoluted it gets.

Not to start another tangent, but it's nice to see someone else leaves their DC power supplies floating!...

beerchug

-Eric

 

[Eric Nelson]

Who thought up THIS ingenious method?

I found some info on SWER at www.ruralpower.org. It's touted as a way to 'help reduce poverty'.

I don't think just killing off the poor folk is the right way to go about it...

They use this schematic to explain how it works:

[sarcasm] WOW! You save one whole wire!... Sign me up! [/sarcasm]

This schematic should be used as the example photo next to the word "Half-a$$ed" in the dictionary. For some people, it might be better than not having electricity, but I'm not too sure I'd be 'happy' once I understood just HOW this electricity was getting to my area...

Having 12.7KV constantly looking to find it's "path of least resistance" underfoot would have me wearing some pretty thick rubber-soled shoes when I went outdoors!

This really brings home Terry's point about 'potential difference' between grounding points!... :nodi:

Or maybe they use R-E-A-L-L-Y long ground rods. Long enough that they actually make physical contact with each other at the center of the earth?...

beerchug

-Eric

 

[Rick Densing]

Interesting article.

Utility liable for stray voltage, high court says

 

[Steve Hite]

Torque increases with slip

 

[rsdoran]

Torque increases with slip

Steve Hite I think we have covered that issue if you read the entire post.

Now fer Eric:

Ron said...

NOTE: The earth can not be "hot"


To which I say... HOT is a "relative" issue.

Take a 120VAC line... tie two taps onto it.
Connect a 500-ohm resistor to each tap.
Connect the other end of one of those resistors to a ground-rod over here (in damp dirt).
Connect the other end of the other resistor to a ground-rod over there (in dry sand).

Measure the current going through each line to its' ground-rod... there will be a difference. Simply because of this difference, there will be a difference in the potential between the connection points on the two rods.

Measure the voltage between the two rods... there will be a potential difference.

(I know you know this Ron,... this is for the kids!)

Ok from the last statement I assume this was to explain HOW or WHY what seems to be EARTH connections are hot.

I just want to state that Eric has shown a VERY GOOD EXAMPLE of HOW there can be a potential difference (voltage) between what seems to be 2 ground/earth points.

This is why I was adamant that EARTH can not be HOT nor will reatain an electrical charge. This example explained why there was a potential difference because of loose/dry sand....ie NOT A TRUE EARTH connection. Things like this can be very frustrating and demanding depending on the issues involved. Thorough investigation may determine where the problem is.

I can give you an honest to god true life experience with an electrical inspector in Atlanta GA coming out in coveralls, no shirt and no shoes after it rained to check the grounds and if equipment was hot...ie touched metal to see if it was "hot".

Grounding or Earth connection issues are a bane to industrial/commercial electricians. They can cause more issues and be more involved to troubleshoot/repair than any other issue known.

If dealing with more than one ground/earth point in a facility I suggest seeking a way to bond those points.....alas I know thats not aalways possible.

As far as articles concerning stray voltages etc...we have been using this stuff for over a 100 yrs now...the details I leave to lawyers and experts when in a courtroom, I believe that most of the issues will involve poor wiring, poor connections and/or poor earth grounds. Who should provide the above is dependent on situation I guess.

 

[Terry Woods]

Before Eric jumps in, Ron... it was from me!

Ron said...
This is why I was adamant that EARTH can not be HOT nor will reatain an electrical charge.

If you mean "EARTH" in the "theoretical sense" that there is ZERO-OHMS between all ground-points including the generating source, then... well, that just ain't the way it is!

Ask your bare-footed inspector!

Ya gotta be "real" when you're talking "grounding"!

 

[rsdoran]

You are right Terry, again I didnt look close enough.

That was my point tho...all thru this, makes no difference what "POINTS" you are refering too..EARTH is a GROUND...same as a neutral point.

IF at any time there is an issue with ANYTHING being hot then the connections need to be checked.

When its all said and done....when everyone shows examples of how...there is one simple fact that stands. THE EARTH IS A GROUND...ie does not become HOT nor retains a potential difference in relationship to another object.

HMM I cant speak for the potential difference between the earth, the moon, the sun and other celestial bodies.

I can speak from the very little knowledge I have. Electricity does nothing..its just there..its a difference in 2 or more points. Apply this electricity to the 2 points of a device then it creates POWER...which does work. A light bulb or motor is an example.

I remember when I was a kid, the refrigerator was always shocking, we (mainly me) would grab someones arm/hand and then grab the fridge door handle...the other person got shocked.

Due to whatever incongruities in design or wiring I have learned there is a reason for items like that to be "hot" or "shocking". Using earth ground was a method designed to eliminate most of those "shocking" experiences.

Its a design that if properly applied will do its job.
Alas I agree that its not alwasys properly applied and does not do the job.

I knew why the inspector was barefooted and did what he did...just amazed me he did it that way. Had hell of a time explaining to my boss what was happening, the Master Electrician in charge of Electrical at the time wasnt much help either

 

[Eric Nelson]

I can give you an honest to god true life experience with an electrical inspector in Atlanta GA coming out in coveralls, no shirt and no shoes after it rained to check the grounds and if equipment was hot...ie touched metal to see if it was "hot".

Are you sure that wasn't just 'standard attire' for the inspector? It gets pretty hot (temperature-wise) in Georgia...

beerchug

-Eric

 

[Tom Jenkins]

"[sarcasm] WOW! You save one whole wire!... Sign me up! [/sarcasm]"

Most of these rural power lines were run in the thirties, late forties, and fifties by Rural Electric Cooperatives. And saving 50% on the wiring was a very big deal - it made running electicity to farms and ranches, sometimes many miles apart, economically feasible.

The cases of milk production fall off from power lilnes are rare and many are apocryphal. The cases of rural lives truly improved by access to electricity are in the millions.

Is there a price to be paid - of course. Was it worth it - Damn Straight it was! Remember, without electricity you had to milk out those cows by hand, you had to carry water from the well in buckets, you had to spend many hours a week washing lamp chimneys, you had to use the thunder mug and the outhouse, you had no music and no news and slight entertainment, you couldn't have central heat, and on and on and on.

By the way, I think that saving one wire by using the earth as a return conductor has a long and respectable history - it was developed in the early days of the telegraph to make THAT system economically feasible.