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Milking Parlour Cows Jumping

Discussion in 'Electrics UK' started by Darkness, 6 Jun 2020.

  1. Darkness

    Darkness

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    Neighbour down the road milks cows. This past two mornings, an hour into milking, the cows started jumping to the roof like they were getting a large shock. It would happen every 10seconds etc in pulses like a cattle fencer/energiser. Would last for a minute or so but the farmer would open the gates and get the cows out and Isolate the electric at the same time.

    Got sparky out but could find nothing wrong and it never did it again after he let the cows out. RCD’s never tripped and the sparky tested them.

    Yesterday morning before a cow was milking, it did it again and the cows were booted out. The farmer has one of those fluke non contact pens and the pen would flash when the cows jumped. It appears the steel work is getting a pulse spike from somewhere. After a minute or two, it never happened again. The sparky was out and again it’s head scratching. No RCD tripped.

    Apparantly it happened last night.

    Anyone experienced this before?
     
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  3. crystal ball

    crystal ball

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    I have seen cattle jumping around in field due to an underground cable fault
     
  4. mattylad

    mattylad

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    Are they making milk shakes?

    Perhaps you need another sparky, one that has some investigating and fault finding skills.
     
  5. Darkness

    Darkness

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    That’s one of the big problems I find with Sparkys. They can nearly all wire but absolutely useless when it comes to fault finding.

    In this case, doesn’t help when the problem could occur for 1-minute in the day.
     
  6. crystal ball

    crystal ball

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    Is the farm near any HV cabling, i.e. substations
     
  7. Robin0577

    Robin0577

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    You could well be looking for two distinctly separate faults there, combining to give that effect.

    1. A fault causing the voltage on the local earthing system to rise. This could be a damaged cable or faulty machinery some distance outside the building concerned, and as such could be hard to track down.

    2. Inadequate or missing equipotential bonding within the building, allowing an unacceptable voltage gradient to build up between two points of contact with the animals. Livestock pens require special attention to earthing and bonding arrangements to ensure that external faults cannot cause this problem. This is achieved by ensuring that anything conductive the livestock can come into contact with is bonded together with very low impedance connections. Often this involves major work such as mesh in the floor structure being bonded.

    Large four legged animals such as cows and horses are particularly sensitive to this kind of thing, simply because of the relatively large distance between front and back legs. There have been several incidents in years gone by where lack of attention to wiring for outside broadcasting of horse racing events has resulted in horses dying while humans nearby felt nothing.

    See section 705 of BS7671 - Agricultural and horticultural premises
     
    Last edited: 6 Jun 2020
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  8. Taylortwocities

    Taylortwocities

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    Needs urgent attention. There’s obviously a ground potential difference and that’s potentially fatal for livestock. Tell farmer to get a proper electrician and not to use Yellow Pages this time.
     
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  9. mattylad

    mattylad

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    Do they happen to have the milk sucking wotsits on their milk giving titty thingies at the time?

    To me thats a potential source if there is some electrics/electronics involved.
     
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  11. Robin0577

    Robin0577

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    I have no experience of milking machines other than what I've seen on the telly, but I was under the impression the cow-to-pump connection would be via insulating plastic hoses. I suppose the milk must have some conductivity of itself though.
     
  12. Darkness

    Darkness

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    No clusters were on the cows and engine vacuum pump hadn’t even starter yesterday morning from what I heard so no milk was in the stainless steel pipes etc. The only thing of 230v that is directly connected to the steel work which the cows stand against when being milked is the pump that pumps the milk from a receiver tank to the main tank outside.
     
  13. SimonH2

    SimonH2

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    The pipework to the clusters (sets of 4 milking cups) is normally rubber/plastic - but bear in mind that a milking parlour is a notoriously wet environment, and the water films on stuff is likely not pure water.
    But, if everything is properly bonded, the milking equipment and all the structural/functional steelwork should all form an equipotential zone. There is typically quite a lot of contact between steelwork and concrete floor, so the concrete should also be part of that zone.

    The farmer needs to get a competent sparky in who knows how to test that the bonding is all intact. Would this need a CT current injection set so that currents can be injected into specific conductors to check that each is properly connected ?
    Obviously, from here we cannot inspect or test anything - we don't know it's TN-C-S, TN-S, TT, or some combination. As said, it does sound a lot like it's PME and there's a potential on the PME earth - if there's no local earth mat then that could well create significant voltages between earthed metalwork and local true earth.
    Could also be worth contacting the DNO.

    One thing is certain, this is a VERY serious situation.

    Looking at section 705, things have changed a bit since I worked on a farm and was helping build the new buildings - but that was <cough> decades ago :whistle: PME earthing, no bonding of structural steelwork (though actually most of it was timber frame). Definitely no earthing grid/mat. The milking parlour is probably the best protected as it has a lot of steelwork, all bonded, and with many connections to wet concrete. I had nowt to do with the electrics, long before I knew enough to be doing that.
     
  14. RF Lighting

    RF Lighting

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    First thing I’d be investigating is the earthing arrangements, and how effective it is.

    Second would be to see if the cows were shocked while touching anything other than the floor such as the stalls / railings.

    Is the milking manual or robotic?

    How old is the electrical installation?

    Is there any re-bar in the concrete floor?
     
  15. bernardgreen

    bernardgreen

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    I recall that milking parlours should be ( must be ? ) TT to ensure a lost Neutral cannot create the hazard of the CPC potential going above true Ground.

    As said it needs a thorough inspection of the electrical and earthing arrangements both in and around the milking parlour.

    This article mentions an electric fence as the source.

    https://www.fwi.co.uk/livestock/dairy/don-t-let-stray-voltage-affect-cow-production-and-cell-counts

    A herd of deer were troubled by electric shocks due to a voltage gradient from the adjacent railway track when a electric train passed by. There was a fault in the track electrification that allowed current into the ground instead of it being forced to return along the Neutral that is strung along beside the track.
     
    Last edited: 7 Jun 2020
  16. FrodoOne

    FrodoOne

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    Since
    I agree with Robin0577 who wrote: -
    Inadequate or missing equipotential bonding within the building, allowing an unacceptable voltage gradient to build up between two points of contact with the animals. Livestock pens require special attention to earthing and bonding arrangements to ensure that external faults cannot cause this problem. This is achieved by ensuring that anything conductive the livestock can come into contact with is bonded together with very low impedance connections. Often this involves major work such as mesh in the floor structure being bonded.

    It is "probable" that the flooring of this area is concrete BUT any steel within this concrete has NOT been bonded together- and to Earth - in accordance with that which now required for concrete around "swimming pools" and under bathrooms.
    A temporary equipotentially bonded "Earthed" metal mesh for the area on which the cows are forced to stand may "prove the point".

    A "long term" fix (of bonding and earthing the steel within the concrete) may not be easy or cheap.
     
  17. SimonH2

    SimonH2

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    Thinking a bit more, as well as addressing the earthing & bonding, a supply quality monitor ought to shed some light on it. I believe DNO are known to put these in when problems are reported. But it would need to be able to monitor between PME earth and local earth.
    Section 705 strongly reccommends against PME earthing but does not prohibit it.
    And as I mentioned earlier, older installations may well be a big standard "PME + bonding of exposed metalwork" setup.
    Thinking more about the farm I was involved with, I don't recall any local earthing, it was all rewireable fuses, no RCDs, and a changeover switch to plug in a tractor driven genny. Some of that is likely to have changed over the ensuing decades, but not much - I'd expect still no local earthing and genny input, on it's own a cause for concern.
     
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