Heated water buckets

[jrfbuildit]

I have a customer who uses heated water buckets for her horses and the horses apparently are shocked when they go to drink water from buckets that are outside, however, they do not get shocked when drinking from buckets inside the barn. I hooked my meter from the ground wire (of the cord) to the bucket and got a zero reading, when I hooked from the ground wire (of the cord) directly to the earth I was reading about 10 volts and when I put the meter from bucket to earth I get a reading of about 6 - 9 volts. From what I see everything seems to be grounded and bonded properly. Is there a way to correct this? BTW she does live about 500yds from high voltage lines.....I don't know if that would make a difference or not. Any help or suggestions would be appreciated.

 

[George Stolz]

You should update your profile to indicate your location.

Sounds like a classic case of stray voltage to me. If you have ascertained that the entire premises wiring system is without defects, then you would need to install an equipotential plane in the areas where the customer wants buckets, and perhaps go so far as to install a site isolating device at the utility transformer. See 547.9 and 547.10.

 

[Dennis Alwon]

I would feed the horses inside. :grin: How's that for advice?

 

[George Stolz]

It's a whole lot cheaper!

 

[LEO2854]

You should update your profile to indicate your location.

Sounds like a classic case of stray voltage to me. If you have ascertained that the entire premises wiring system is without defects, then you would need to install an equipotential plane in the areas where the customer wants buckets, and perhaps go so far as to install a site isolating device at the utility transformer. See 547.9 and 547.10.

I agree with George here is a good link on equipotential plane. http://www.lni.wa.gov/tradeslicensing/electrical/files/currents/elc9906.pdf


Welcome to the forum

 

[jrfbuildit]

buckets

buckets

Thanks guys, I appreciate your input. I should mention that I am reading approx. 6 - 10 volts even when I am about 100 yds away from the barn. Is there a way to trace stray voltage? (ie. higher voltage closer to source)

 

[Dennis Alwon]

Thanks guys, I appreciate your input. I should mention that I am reading approx. 6 - 10 volts even when I am about 100 yds away from the barn. Is there a way to trace stray voltage? (ie. higher voltage closer to source)

This could very well be a utility problem.

Turn the main off and see if the voltage still exists. If it is gone then some underground wire to the barn may be the issue.

 

[ceb58]

You could also(carefully) check around the high voltage lines. There could be voltage bleeding off the grounds on the pole/tower leg.

 

[hurk27]

6-9 volts is in the range I wouldn't suspect a lost neutral problem but is in the range of maybe a voltage drop problem of the feeding neutral to this barn, or the service neutral, and even could be the voltage drop of the utility's MGN.

If this is a typical farm type service where you have the meter and disconnects all located on a pole with feeders to each building then most likely you only have 3-wire feeders to each building, if turning off the power at this pole for the affected barn eliminates the voltage this will indicate that the voltage drop is on this neutral, if this doesn't eliminate the voltage then it is the voltage drop of the service neutral or MGN.

If you determine it is the neutral feeding this building, you have but two choices.

Choice 1: to me would be the best choice is two add a separate EGC from the service disconnect to the barn, separate the grounding and grounded conductors at the barn as would be done for a sub panel, this will keep the neutral voltage drop from appearing on the grounding for this barn.

Choice 2: calculate the correct size neutral conductor as per load to lower the voltage drop, not the best thing to try to do since farm animals can sense voltage as low as .5 volts.

If you determine that the voltage drop is ahead of the service point, you might have to get the utility involved to isolate it to see if it is the service drop or the MGN, this would be done by removing all power from the service then checking to see if the voltage is still there, if it is then its the MGN, if not its the service neutral.

How far is the serving transformer from the service disconnect?
If it is over 200' you might be able to get the utility to add an isolated EGC from the transformer to the service, but because most meters have the neutral bonded to the can, it is very hard to find one that can be isolated, again separating grounding and neutrals at the service as if it was a sub panel would be a must.

Relocating the transformer closer to the service point is also an option but can be hard to get done if there is no closer right of way for the primaries.

If it turns out to be that the voltage is in fact coming from the MGN, the only method I know of ( that Will be cost effective for the serving utility) is to have the utility to install a neutral block device at the transformer, this isolates the secondary neutral from the primary neutral (MGN)

I highly doubt that the voltage is from the HV lines passing above this area, for the most part this capacitive coupled voltage will be shunted via the earth in short order, as for voltage from the tower legs, I cant see how any voltage can be on these legs as these towers have multiple points of bonding to the static conductors that run with the HV phases, and each tower is bonded multiple times to very long and deep grounding electrodes installed at each and every tower.

Will voltage build up on a conductor in close proximity to a HV transmission line? sure it will if it is isolated, but shunt it to earth even with a very high resistance load and it will go back to zero.

Also the fact that voltage does not travel very far through earth before being brought to the Earth potential of 0 volts.

It is the problem of other conductors that are used in the grounding path such as the system neutral that have a voltage drop on them when current is applied that will raise the voltage to a point above Earth that will give you this difference of potential.

 

[ptonsparky]

Underground or overhead to the barn?
Check underground for faulted conductors. Use a meggar.
You may have good voltage and balanced but still have a faulted conductor.
Check incoming voltage at panel, line to line and line to neutral.
Clamp an amp meter around all the service conductors. Both hots and neutral. Does it read zero?
Check other buildings and see if all is correct at them. A problem with the machine shed is a problem in the horse barn. Check the well pump motor.

We always install GFCI protection for livestock equipment. Meg the heaters.

 

[dbuckley]

If you have ascertained that the entire premises wiring system is without defects, then you would need to install an equipotential plane in the areas where the customer wants buckets, and perhaps go so far as to install a site isolating device at the utility transformer.

Agreed.

But if these are plumbed in water troughs unplug the heater first to make sure this isn't a issue that exists without the electrical heaters being involved, which is actually fairly common.

One other alternative to extensive remedial works is an isolating transformer to feed the bucket. it must be a plug-in isolating transformer, so it is not part of the building wiring, otherwise it falls under the SDS rules and then isn't an isolating transformer anymore. A transformer with an entirely floating secondary with respect to the primary and (most importantly) the primary ground.

You need one per trough, because if you use transformer to feed multiple troughs, and you get a double fault, it could be deadly to horse and people.

 

[jrfbuildit]

I shut off the main power in the house and was still getting stray voltage in the earth. The transformer two houses down has a disconnected ground (hit with lawnmower I assume) I tested the hanging ground at the utility pole and was getting close to the same reading at the barn. Is this possible even though the transformer close to the house seems to be ok? I will call poco to report the problem....hopefully this will work. Thanks guys and Merry Christmas!

 

[dkidd]

Check out

http://www.omafra.gov.on.ca/english/livestock/dairy/facts/strayvol.htm

and

http://www.pacificpower.net/content..._Suppliers/Power_Quality_Standards/1C_7_1.pdf

and

http://www.pge.com/includes/docs/pd...er_quality_bulletin-issue_no.2_stray_volt.pdf

Having attended a recent seminar given by Mr. Holt, I learned that there are voltage gradients in most utility grounding systems..

As stated in the second document:

"Low levels of ac voltage on the grounded conductors of a farm wiring system are a normal and
unavoidable consequence of operating electrical farm equipment. Stray voltage is the general
term used to describe these low-level voltages when they are measured between two objects that
can be contacted simultaneously."

The best solution is probably an equipotential grid

 

[hurk27]

I shut off the main power in the house and was still getting stray voltage in the earth. The transformer two houses down has a disconnected ground (hit with lawnmower I assume) I tested the hanging ground at the utility pole and was getting close to the same reading at the barn. Is this possible even though the transformer close to the house seems to be ok? I will call poco to report the problem....hopefully this will work. Thanks guys and Merry Christmas!

Explain the problem to the POCO, maybe showing them info on stray voltage that can cause this from their MGN, then tell them that there is a device called a neutral block that can be installed to eliminate the problem, and it will still protect against a fault across the transformer.

6-10 volts can be very serous if this is around any body of water, even a pool would be dangerous to use with this much voltage differential.

 

[jusme123]

...have the horses fitted for a pair

ok, I'll quit horsing around

 

[Tom C]

Years ago the trough heater manuals asked for a ground rod and bare conductor put in the tub. Don't know how well that would work for buckets.

 

[tkb]

...have the horses fitted for a pair

ok, I'll quit horsing around

I would get Red Wings.

 

[jrfbuildit]

update

update

I called the POCO and they sent a tech out to measure the voltage.....tech left message both times that we had 120v/240v at the meter. Am I missing something? It seems when you report a problem to these big companies everything gets lost in translation. I met with the tech and explained to him my problem with the stray voltage and at the same time I pointed out the cut ground line to the transformer to which he replied to me, "that that is not my department" and a different tech would have to come out. I'm getting frustrated.

 

[Rick Christopherson]

It is a common misconception that the Earth is at zero volts and remains the same everywhere. This is not true, and it is not entirely related to our power distribution systems. Even if you shut off all the power in the world, there would still be voltage gradients from natural effects.

Having a voltage difference between the grounding conductor and the physical earth does not automatically indicate a problem. This is also a very common problem with livestock troughs. (My sister's horse farm also experienced the same thing.) Consider a 9 volt battery. You can touch the terminals and not feel a thing, but touch it to your tongue and you can "taste" the voltage.

You are looking for a problem that may not exist. The grounding conductor (assuming no current on it and therefore no voltage drop) will be at the same potential as the physical earth location of the main grounding system. The physical earth at the trough will be at some other potential. The standard solution for this is to drive a ground rod at the trough.

By the way, it is also possible (and very likely) that the main grounding electrode system is elevating the local earth potential at the electrode(s) due to current flow (which is almost always present). Even dirt has to follow Ohm's Law, and any current in the ground system will result in a voltage difference.

 

[don_resqcapt19]

...

You are looking for a problem that may not exist. The grounding conductor (assuming no current on it and therefore no voltage drop) will be at the same potential as the physical earth location of the main grounding system. The physical earth at the trough will be at some other potential. The standard solution for this is to drive a ground rod at the trough.

By the way, it is also possible (and very likely) that the main grounding electrode system is elevating the local earth potential at the electrode(s) due to current flow (which is almost always present). Even dirt has to follow Ohm's Law, and any current in the ground system will result in a voltage difference.

It is very unlikely that a single ground rod at the trough will solve the problem. The earth to rod contact resistance, and the resistance of small areas of the earth itself, is just too high for that to work. It will likely take an equal potential grid around the trough to solve the problem if you cannot eliminate the voltage by other methods.

Given the utility use of MGN systems, it is very likely that you are putting voltage to the earth at the point of the service grounding electrode. This same elevated voltage will be on everything connected to the electrical grounding system as measured to remote earth (by definition earth 50 or more feet away from the service grounding electrode). In the case of the heated buckets, the EGC will have an elevated voltage as compared to the earth in the area of the buckets. There are a few ways to eliminate this voltage...a neutral blocker installed by the utility, if they will do it, an isolation transformer (but very difficult to get the required primary to secondary isolation and make the installation compliant with the rules in the NEC) or a equal potential grid in the area of the water buckets. In most cases the last method will be the easiest.