D
Deleted member 18243
Bernard, that link does not work.
Milking Parlour Cows Jumping
- Thread starter Darkness
- Start date
Bernard, that link does not work.
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Try this :- maybe have to cut and paste into your browser
https://www.fwi.co.uk/livestock/dairy/don-t-let-stray-voltage-affect-cow-production-and-cell-counts
Several sites seem to be un-reachable when the link is via DIYnot
https://www.fwi.co.uk/livestock/dairy/don-t-let-stray-voltage-affect-cow-production-and-cell-counts
Several sites seem to be un-reachable when the link is via DIYnot
Nat all statements in that article are correct!
"Stray electricity occurs when voltage is unable to make its way to the main earthing system and a natural path for voltage to travel back to earth in a milking parlour is the steelwork."
There is no such thing as "stray electricity".
There is only current returning to its source (either intentionally or by a "fault" condition) via any and all paths which are available.
If none of these "paths" are of zero resistance, a potential difference will exist, proportional to the total parallel resistance of those paths.
This forms a "potential gradient" across any resistive "ground" surface which is involved.
The statement could be better put by writing : -
"A voltage (potential difference) will exist between different points on any "ground" surface when a current returning to its source flows through a ground path where the resistance is greater than zero."
"Steelwork" will have a very low resistance, when each piece of it is "bonded" to every other piece in the same area.
(i.e. Each and every piece of steel will then be at the same potential.)
If the steel is also "bonded" to the "Main Earth" connection, it will be at the same potential as that "Earth" connection and, thus, at (or very close to) the potential of the Neutral - because the Neutral is connected to "Earth", either Remotely, Locally or Both.
"electric fences should always have a separate earth at least 20 m from the mains earth."
It is unlikely (and undesirable) that, in any "mains powered" Electric Fence power supply, the "Protective Earth" incoming from the "mains" will be connected to the "Earth" for the "output" of the "Fence" supply.
The "output" for the Fence is "isolated" from the "mains" (and its PE), hence separate (independent) "Earth" rods are required.
These "Earth" rods should be close to the "line" of the fence and, if possible, underneath it.
This is because there will always be some "leakage" current from the "Output" wire of the fence to the earth (via dampness, grasses etc.), which will return to the "Earth" rods via the resistive paths of the earth itself. If there are many points of "leakage" along the fence, the "potential gradient" across the ground near the "Earth" rods is likely to be quite high.
This potential gradient is likely to be felt by any animal with widely spaced bare "feet" standing in the area concerned. If that "area" is close to the fence, it discourages the animal from going there - which is not undesirable. However if the "Earth" rods are placed away from the fence (which is inefficient), such animals will be discouraged from going to the area between the fence and the "Earth" rods - which may be quite undesirable.
Hence,
"electric fences should always have separate earth rods under, or close to, the fence line."
"Stray electricity occurs when voltage is unable to make its way to the main earthing system and a natural path for voltage to travel back to earth in a milking parlour is the steelwork."
There is no such thing as "stray electricity".
There is only current returning to its source (either intentionally or by a "fault" condition) via any and all paths which are available.
If none of these "paths" are of zero resistance, a potential difference will exist, proportional to the total parallel resistance of those paths.
This forms a "potential gradient" across any resistive "ground" surface which is involved.
The statement could be better put by writing : -
"A voltage (potential difference) will exist between different points on any "ground" surface when a current returning to its source flows through a ground path where the resistance is greater than zero."
"Steelwork" will have a very low resistance, when each piece of it is "bonded" to every other piece in the same area.
(i.e. Each and every piece of steel will then be at the same potential.)
If the steel is also "bonded" to the "Main Earth" connection, it will be at the same potential as that "Earth" connection and, thus, at (or very close to) the potential of the Neutral - because the Neutral is connected to "Earth", either Remotely, Locally or Both.
"electric fences should always have a separate earth at least 20 m from the mains earth."
It is unlikely (and undesirable) that, in any "mains powered" Electric Fence power supply, the "Protective Earth" incoming from the "mains" will be connected to the "Earth" for the "output" of the "Fence" supply.
The "output" for the Fence is "isolated" from the "mains" (and its PE), hence separate (independent) "Earth" rods are required.
These "Earth" rods should be close to the "line" of the fence and, if possible, underneath it.
This is because there will always be some "leakage" current from the "Output" wire of the fence to the earth (via dampness, grasses etc.), which will return to the "Earth" rods via the resistive paths of the earth itself. If there are many points of "leakage" along the fence, the "potential gradient" across the ground near the "Earth" rods is likely to be quite high.
This potential gradient is likely to be felt by any animal with widely spaced bare "feet" standing in the area concerned. If that "area" is close to the fence, it discourages the animal from going there - which is not undesirable. However if the "Earth" rods are placed away from the fence (which is inefficient), such animals will be discouraged from going to the area between the fence and the "Earth" rods - which may be quite undesirable.
Hence,
"electric fences should always have separate earth rods under, or close to, the fence line."
I recall that on the farm I was involved with, the farmer bought a mains powered fence unit designed for very long fences in New Zealand. We only used the low power output, the full power one was just too scary 
We used it around the buildings as an alternative to having to build lots of strong and rigid fencing - easier to just string a wire, which was also easy wind up for easy access for tractors etc. I can't remember what we did for the fence earth - I've an idea we just stuck a bit of bar in the ground - sited "where we could".
It's funny ...
For a few years, milking was in part of one of the cubicle houses that we'd adapted into a parlour - he built a proper parlour eventually. But for some cows where the milk wasn't going into the bulk tank (newly calved, on medication, etc) he use one of the very old standalone milking units with it's own bucket. One morning, farmer went to dairy to get the milking unit, and on the way back "dipped down" to go under the electric fence. He reckons his head must have touched the wire because he had a gap in his memory between crouching down and waking up flat out on the floor. Of course we were all so full of sympathy
We used it around the buildings as an alternative to having to build lots of strong and rigid fencing - easier to just string a wire, which was also easy wind up for easy access for tractors etc. I can't remember what we did for the fence earth - I've an idea we just stuck a bit of bar in the ground - sited "where we could".
It's funny ...
For a few years, milking was in part of one of the cubicle houses that we'd adapted into a parlour - he built a proper parlour eventually. But for some cows where the milk wasn't going into the bulk tank (newly calved, on medication, etc) he use one of the very old standalone milking units with it's own bucket. One morning, farmer went to dairy to get the milking unit, and on the way back "dipped down" to go under the electric fence. He reckons his head must have touched the wire because he had a gap in his memory between crouching down and waking up flat out on the floor. Of course we were all so full of sympathy
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Manual milking system and the farmer says all the wiring was done new around 7years ago when they upgraded the parlour. Everything is done in conduit/swa/hi-tuff. No mesh in floor as it wasn’t a new building/install and couldn’t be done during upgrade as cows had to be milked twice a day.
Rang the farmer this morning and everything has been fine since Saturday and two sparkys that we’re out did tests and everything seems fine. He says they are there today redoing the earthing setup, new earth rod etc as a precaution and doing some bonding.
One thing he stated was the days the problem occurred, it was raining and quite windy. A few metres from the parlour is an electrical pole which takes two electrical cables to the farm from the transformer on the pole. These two cables go through a tree and touches the branches. He has requested the tree to be taken down by the electricity supplier but the won’t take it down. They trim a few twigs. It’s old 30yrs plus, overhead cables and one cable could be a bare cable so the sparkys had raised the question of the tree having something to do with the shock when it gets wet and since yesterday and today is dry, it has been fine.
That and the tree could well be the source of the problem. Especially if as you say one of the cables is an un-insulated wire.
The case of the transformer will ( should ) have a ground rod and this could be introducing current into the surrounding ground.
They probably aren't allowed to take the tree down as it isn't their's. There's probably some statutory right for them to trim stuff, but not remove it altogether.
Is it the farmer's tree ? If so, then he can take it down himself - though he'll need to arrange with the DNO for them to turn off the power, and possibly repair the cable if it gets broken during tree felling.
Is it the farmer's tree ? If so, then he can take it down himself - though he'll need to arrange with the DNO for them to turn off the power, and possibly repair the cable if it gets broken during tree felling.
We had the electricity people here last year doing routine checks on trees growing near power lines.
The very helpful man said they have the power to trim branches to a safe distance, without permission if no one was around.
We walked along the length of the wires and agreed a list of all the work he proposed doing. A few trees were cut to the ground, some were cut to a height of about 10 feet. Basically he would do whatever I wanted, as long as it exceeded their minimum requirement.
He said he would leave the logs in a stack if I wanted them, to which I obviously agreed, and he asked how long I wanted them? I jokingly said about 9" would be handy, and he laughed. He cut them to 4' and left them in a series of neat stacks. They chipped all the small stuff and would leave it in piles if required.
The only thing they won't do is dig out the stumps.
He seemed very knowledgable about trees, and gave advice about ash die-back, commented about which of ours looked doomed and which showed signs of recovery, and also advised against letting a particular kind of maple get established as it was notorious for sending up suckers a long way from the main tree.
All free.
I should have said that an un-insulated Live rubbing on a tree branch can create significant ( cow tickling ) voltage gradient in the ground between tree and any nearby Earthed items ( milking parlour metal work ). The current flowing down through the tree will be looking for the easiest ( lowest impedance ) path back to the Neutral at the substation ( or pole transformer ).
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