Cattle deaths

There used to be dire warnings about using the TT installation electrode as an electric fence earth electrode, the danger being that a fault on the installation raising the voltage on the electrode could lift the voltage on the fence to lethal levels.


Andy Betteridge

A team from the DNO were on site yesterday. I was there as well but little in the way of communication between us as I imagine they realise that litigation is likely. Nonetheless the engineer did say that all was sound on their side with both the HV and LV earths falling well within their 40/20 ohm requirement. In fact the LV earth was recorded at just under 12 ohms. Not sure how the measurements were taken but my loop impedance test on the shed steelwork with all other earths disconnected was just below 5ohms. The shed in question is quite some distance away.

I wonder if the DNO are sure there is no underground cable fault present ?


I think a long lead and a voltmeter testing between the supply earth and and exposed and extraneous parts would be a useful exercise kitted out with rubber boots for PPE. The and between exposed and extraneous  parts. Followed by the Capon test between a long screwdriver stuck in the ground and exposed and extraneous conductive parts.

you may find a garden fork and a croc clip makes a better temporary earth, especially if like me your longer screwdrivers are insulated.  Expact a Ze of 50-500 ohms from the garden fork in full depth.

For contact onto concrete, tarmac or other 'hard' surfaces a contact can be made with a salt water soaked old towel or similar and a bundle of bare wire or a stainless steel pan scrubber pressed into service if you only need to pick up enough to make a volt meter indicate (no good as a real safety of life earth of course but OK for finding voltages over a 'footprint' sort of area.)

Ze in such a case is a bit nebulous but is a representative  measurement phantom for the situation of a sweaty bare-foot contact, and much more convenient and humane than using a real persons foot.

Be aware that you will see some  DC anyway, as the saltwater and the electrodes form a crude battery, and both ends are most unlikely to be identical voltages. voltages at 50Hz AC however, should be considered as more real, though if it all vanishes when any current is drawn, it is not serious. If however you can get mA to flow then investigation is needed.

When I said about knocking up a wooden frame with some nails in it to replicate the likely span between the cattle’s feet I was forgetting about the nose and tongue, it would actually need five nails positioned accordingly.

The diagram in this article suggests there can be the full voltage gradient 230 volts to zero across a cow on soil.


 Andy Betteridge

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 

Before Mr Betteridge gets too excited, electrocution amongst cattle is rare especially those numbers, the most common cause of cattle deaths is one of the Clostridial diseases, most of them tend to be rapid and fatal, Clostridia is part of a family of anaerobic bacteria found in the soil and farm environments, grass, hay and water, it does take a while to spot as cultures have to be developed to identify the particular strain, just an observation.


Rob.