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Cattle deaths

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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  • A typical “healthy” 100mA RCD could be letting 70 mA of current flow through the building without tripping.


    The last farm I went to do work in the farm house did not have any RCD protection to the farm building supplies at all. The buildings installation originally had its own meter, to save money the meter had been removed and the tails dogged into the house meter tails before the old VOELCB for the house installation without a RCD being installed, all TT.


    I have learnt to be very careful when testing installations like that, I went to a house where I had already told them to get an earth rod and RCDs installed several years prior. They said they had a problem with the lights, when I tested at the main switch, double checking with a test lamp I found:


    L-N 240 volts + lamp lit.


    L-E Zero volts + lamp did not light up.


    N-E 240 volts + lamp lit.


    When you discount reversed polarity on the incoming supply the only option left is that every bit of earthed metalwork in the house is sitting at 240 volts including all the appliances and decorative metal electrical accessories, 


    There follows a quick Oh **** ! moment. Then you start dead testing to find the cables the rats have chewed and wee’d on.


    Going back to the post it seems logical to me if the lights are mounted on the steel frame of the building or the cables cross it, then the stanchions are more likely to be a source of concern than the floor and I would start testing around them.


     Andy Betteridge 


Reply
  • A typical “healthy” 100mA RCD could be letting 70 mA of current flow through the building without tripping.


    The last farm I went to do work in the farm house did not have any RCD protection to the farm building supplies at all. The buildings installation originally had its own meter, to save money the meter had been removed and the tails dogged into the house meter tails before the old VOELCB for the house installation without a RCD being installed, all TT.


    I have learnt to be very careful when testing installations like that, I went to a house where I had already told them to get an earth rod and RCDs installed several years prior. They said they had a problem with the lights, when I tested at the main switch, double checking with a test lamp I found:


    L-N 240 volts + lamp lit.


    L-E Zero volts + lamp did not light up.


    N-E 240 volts + lamp lit.


    When you discount reversed polarity on the incoming supply the only option left is that every bit of earthed metalwork in the house is sitting at 240 volts including all the appliances and decorative metal electrical accessories, 


    There follows a quick Oh **** ! moment. Then you start dead testing to find the cables the rats have chewed and wee’d on.


    Going back to the post it seems logical to me if the lights are mounted on the steel frame of the building or the cables cross it, then the stanchions are more likely to be a source of concern than the floor and I would start testing around them.


     Andy Betteridge 


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