Harmonics and dairy cattle

[ptonsparky]

George,

The primary neutral has current flow and therefore has voltage drop. Remember that even a 1% drop can be a lot of voltage at the primary level. The earth is in parallel with the primary neutral. The current flows through the earth in an unknown path. If you are remote from this path, and you measure from the electrical system grounding system to this remote earth you are measuring the voltage drop on that primay conductor.
Don

How do we tell the difference?

When I took voltage measurments from neutral to a remote ground rod and disconnectied a Dairy from Utility power the resulting reading would have been primary voltage drop? We called the difference "On farm/Off farm"

If the current flows in an unknown path how do I know when I am remote from it?

 

[don_resqcapt19]

ptonsparky,

How do we tell the difference?

When I took voltage measurments from neutral to a remote ground rod and disconnectied a Dairy from Utility power the resulting reading would have been primary voltage drop? We called the difference "On farm/Off farm"

If the current flows in an unknown path how do I know when I am remote from it?

There is no good answers to this type of problem. One of the first checks would be to check for voltage to earth with the farm service disconnected. When you make that check you are really reading the primary grounded conductor voltage drop, or the seconday grounded conductor voltage drop on any other services fed from the same transformer. Often the problem will be a combination of utility side and farm service side issues. The most common problem on the service side would be multiple grounded to grounding or earth connections.
Don

 

[brian john]

One thing I have learned when tracking down electrical problems is try everything in a variety of conditions, power on power off, certain loads on certain loads off. Measure ground current at all accessible points, take voltage readings at a variety of locations. Do not get frustrated and keep at it.

I own a variety of clamp on amp meters (leakage level meters and full scale meters), large CT's, flexible CT's and numerous multimeters, this allows you to take reading at a variety of locations, around I-beams, around all phase conductors and neutral/grounded conductor.

Do not get frustrated, keep at it, many times I put in extra non billable hours, to locate problems. But when you finally isolate the discrepancy, you'll feel great and look like a prince to you customer.

Oh, never be afraid to call or ask questions of other electricians.

There are no dumb questions.

My ex-father-in-law once told me a man/woman created the problem, a man/woman should be able to figure out the solution. He actually left out the woman part, but this was in the 60?s

 

[George Stolz]

If you are remote from this path, and you measure from the electrical system grounding system to this remote earth you are measuring the voltage drop on that primay conductor.
Don

So, let's look at an example to see if I've got this right:

• voltage is detected on a water tank
• there are no deficiencies in the premises wiring, or they've been corrected
• the voltage is present and detectable from tank to earth nearby when the service is off

...then the grounding electrode system of the premises is at a different potential than the earth around the tank. The tank is nearly the same potential due to electrical connections.

There is either a potential in the earth around the tank, and the lack of voltage at the earth surrounding the GES is making it evident, or the other way around - either/or.

Does that sound close?

 

[don_resqcapt19]

George,

There is either a potential in the earth around the tank, and the lack of voltage at the earth surrounding the GES is making it evident, or the other way around - either/or.

Everything connected to the electical grounding system has an elevated voltage when compared to "remote" earth. This voltage elevation is equal to the voltage drop on the grounded conductors.
Don

 

[George Stolz]

Compared to remote earth, yes. What if a SWER path lay underneath the tank, elevating the voltage of the earth around the tank, and the GES was not in an elevated area?

In that case, the GES compared to a third remote earth point would be higher, but the earth surrounding the tank would be higher still, right?

Or does that ever happen?

Thanks for explaining this, Don.

 

[ptonsparky]

One last thought then I'm done. Maybe...

Assume the dairy has largest GEC in the area back to utility and that it has the best GES including several thousand sq ft of equipotential plain. IMO this makes the dairy a “sink” compounding the problem of primary neutral voltage drop for the surrounding area. Yes/No?

 

[don_resqcapt19]

Assume the dairy has largest GEC in the area back to utility and that it has the best GES including several thousand sq ft of equipotential plain.

If there really is an equipotential plane, then there is no voltage between the plane and anything connected to it.
Don

 

[don_resqcapt19]

Compared to remote earth, yes. What if a SWER path lay underneath the tank, elevating the voltage of the earth around the tank, and the GES was not in an elevated area?
In that case, the GES compared to a third remote earth point would be higher, but the earth surrounding the tank would be higher still, right?
Or does that ever happen?

It is very difficult to raise the voltage of the earth for more than a few feet around the electrode.
Don

 

[George Stolz]

So (to make sure I'm getting this right), the premises wiring system GES is always going to have a higher potential than any earth remote from the system?

I mean, never say never, but we can wager serious money on it?

 

[don_resqcapt19]

George,

So (to make sure I'm getting this right), the premises wiring system GES is always going to have a higher potential than any earth remote from the system?

Yes.
Don

 

[ramsy]

Assume the dairy has ..several thousand sq ft of equipotential plain.

Or, use isolation Xfmrs with L-L circuits, no white wire.

 

[George Stolz]

Right on, thanks Don.

 

[jinglis]

This sounds like tingle voltage. It can originate from a fault at a neighbouring farm. I have also heard of tingle voltage filters to help with or eliminate this problem. I had a service call once for a report of getting shocks in the vicinity of their swimming pool. I started with one lead of my DMM in the water with the other lead on the handle of the steel ladder. It was a measurable voltage. I shut down all the electrical equipment in the vicinity of the pool and the voltage remained. I went to the house and shut down the main switch. The voltage remained. I called the utility to assist in determining if their underground service feed could have a problem. The end result was the shed their next door neighbours had recently powered up. Once the power to it was shut down the voltage at the pool disappeared. I didn't get a chance to determine the exact problem but I simply disconnected the power to the shed permanently for safety reasons and asked the homeowner to deal with the problem through his own electrical contractor.

 

[Vincent_ruby]

Dairy Cattle Give Milk

Dairy Cattle Give Milk

So don't eat the beef. I also never worked inthese types of conditions. Let's
face it I never got a charge out of a glass of milk in the morning. When adding to coffee the charge lessened. Was this due to negative vs positive.

 

[beanland]

Harmonics <> Strey Voltage

Harmonics <> Strey Voltage

I have addressed stray voltage problems at dairies. The cattle are sensitive to very low levels of stray voltage (mouth to feet, between feet, udder to feet, etc.) Proper control is to first provide a fully grounded dairy, all fences, gates, rebar, pipes, feeders, anything. Bond them, ground them, and bond them again. Clean old clamps or weld the grounds. You need to make sure that all neutral return currents (including capacitive coupling) return through the neutral, not the ground. Make sure all neutrals are isolated, neutrals are well insulated, make sure there is no leakage current from neutral to ground because of water, etc. The expensive devices are neutral isolators that allow the utility neutral to float (no local ground) but then tie the two together if there is a fault (to make sure there is good current). NEC allows neutral isplators to mitigate problems with undesired ground/neutral currents. The local Dairy Association and utilities have good information.

 

[ghostbuster]

The enclosed link is loaded with info on cattle and the stray voltage problem.
http://www.strayvoltage.org/

 

[tom baker]

The biggest source of the stray voltage is the voltage drop on the utility primary grounded conductor. This conductor is bonded to earth at least 4 times per mile as well as at each transformer where it it connected to the secondary grounded conductor. This places the earth in parallel with both the primary and secondary grounded conductors and will often result in stray voltage problems. These problems are most often noticed at dairy farms and pools where the low level voltage causes problems.
Don

And the further you are from the utility substation the greater the voltage drop and more current in the earth.
Mike Holt in his excellent grounding vs bonding seminars covers this very well.
You can not remove this voltage from the earth. The equal potential ground grid only hides it, ala bird on the wire.

 

[donjohn]

Stray voltage

Stray voltage

I am an electrical engineer and have dealt with stray voltage for many years, typically on dairy farms. Right now I am providing assistance in a lawsuit in Minnesota where over 350 dairy cows were lost due to stray voltage. Concerning harmonics typically the only harmonics that last very long or travel very far are the odd harmonics, 3rd, 5th, etc. The even harmonics are normally canceled out. Usually the 3rd harmonic is the only one of any significance. Usually the only way to verify if harmonics are a problem would be to have someone come out to your facility with an oscilloscope to see what frequency of the stray voltages are. Just shooting from the hip I would suspect that you are only dealing with the fundamental frequency of 60 hz. If you want to e-mail me through this forum I would be happy to provide you some additional information in determining the source of your stray voltage.
Don

 

[ServiceTech1/c]

Oh just turn up the voltage and stop when they are medium rare. I hate well done beef YUCK

hehehehehe......