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Cattle deaths

lyledunn
Some 10 prize bullocks died in quick succession whilst housed over winter in a cattle shed. The government vet was unable to reach a conclusion on cause but apparently does not discount electric shock as an indirect cause. 

The shed comprises steel columns and trusses with corrugated iron sheeting over. The floor comprises re-Inforced concrete slats over the slurry tank. The pens have steel barriers supported by steel posts all of which are heavily corroded but still making contact with other albeit fortuitously.

The earthing system is TT with the shed steelwork on its own providing a substantially low impedance of 5 ohms using a loop tester. A 100mA RCD protects the rather ropey lighting circuits.defccf32df3c757507a0db6ad0a35f87-huge-a5af3537-8eae-4a3c-9126-68fa60b61ac7.jpg

whilst the floor could be wet, I can’t conceive how a voltage difference could be established even if the steelwork was at 230v

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    In the original post Lyle said “I can’t conceive how a voltage difference could be established even if the steelwork was at 230v”.


    If the roof has steel trusses siting on steel stanchions, but timber purlins between them presumably they could have a voltage difference between them.


    The steel slats of the floor are sitting on concrete sleeper walls and presumably could have a voltage difference within the span of a bullock.


    The first impression from looking at the photo is there lots of interconnected steel work, but actually it’s probably not as connected as it may appear.


    There has not been any mention of were the lighting is mounted or what other circuits there are, if any.


    I think it’s probably okay to assume there could be a voltage difference from the stanchions yo the floor and across the floor, without doing much testing.


    Given the low earth reading of 5 ohms if there is a fault it has livened up something that is not bonded on either on purpose or gratuitously and is not serving as an earth electrode itself, as tends to be assumed with a stanchion or something bolted to one.


    I would knock off the main switch, interconnect the live and neutral in the distribution board then connect a long wander lead to the live and neutral in the DB and an insulation tester to the other end of the wander lead; then I would start by doing an insulation test to every stanchion, every other bit of metal work in the roof frame then run the tester across the steel floor.


    I would make up or buy a long pole to test the roof, rather than trying to do it off a ladder.


    Then a cable running over a steel truss that has been damaged may be found or something similar.


    Andy Betteridge 


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  • 0
    In the original post Lyle said “I can’t conceive how a voltage difference could be established even if the steelwork was at 230v”.


    If the roof has steel trusses siting on steel stanchions, but timber purlins between them presumably they could have a voltage difference between them.


    The steel slats of the floor are sitting on concrete sleeper walls and presumably could have a voltage difference within the span of a bullock.


    The first impression from looking at the photo is there lots of interconnected steel work, but actually it’s probably not as connected as it may appear.


    There has not been any mention of were the lighting is mounted or what other circuits there are, if any.


    I think it’s probably okay to assume there could be a voltage difference from the stanchions yo the floor and across the floor, without doing much testing.


    Given the low earth reading of 5 ohms if there is a fault it has livened up something that is not bonded on either on purpose or gratuitously and is not serving as an earth electrode itself, as tends to be assumed with a stanchion or something bolted to one.


    I would knock off the main switch, interconnect the live and neutral in the distribution board then connect a long wander lead to the live and neutral in the DB and an insulation tester to the other end of the wander lead; then I would start by doing an insulation test to every stanchion, every other bit of metal work in the roof frame then run the tester across the steel floor.


    I would make up or buy a long pole to test the roof, rather than trying to do it off a ladder.


    Then a cable running over a steel truss that has been damaged may be found or something similar.


    Andy Betteridge 


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