Cattle deaths

As a one time cadet, the wisdom of the time (if outdoors in a lightning storm) was to get down, curl up and try to cover your head - the old hands used to do this - we were then told to adopt the "lightning crouch" to minimise ground contact whilst still keeping low


It was like a bloody stress position


OMS

I riding stables where I used to ride found 4 horses dead one morning under a large tree after a a night of thundering and lightening. A horse's heart is just behind it's near fore leg so is positioned between it's front legs and back legs so some distance apart for a step potential. Fit metal shoes on each leg and standing on wet ground just adds to the risk.


If you look at the video of the horses that were killed at Newbury race course the horses were rearing up to relieve the the pain they were suffering. Could this situation be an underground cable fault the same as Newbury?

As a complete guess and a throw it out there ideas (some are stretching it a bit though):


Does the supply arrive at the shed as a TN system of some sort and then become a TT System? And has the 100mA RCD been installed downstream of the TN divide?  

705.411.1 (iii) - "all other circuits"  such as slurry pumps or mixers may have a 300mA RCD on them - or not have any at all - perhaps there is a afault on one of these circuits?

Water pumps/pressure jet set maybe..........You only mentioned the one 100mA RCD - so perhaps that covers everything?

All that slurrey/soil would possibly insulate those (one or more) metal slatts over the slurrey pit affecting the ohms to earth reading and how well its connected to earth, que in a fault current, And then the cow steps on a well earthed slat with its front or back legs and bam.........just guessing here though.

Shelter from lightning below trees, is a common source of fatalities for all animals in warmer climes. White, naked pine trees with bark stripped all the way down were a common sight, probably because of the lower resistance path at the bark. I suspect that the cause of the fatalities in this post, is deficient earthing and infrequent test reports, unfortunately, the cattle are the testers. I've experienced 2 instances of a loud crack and damage, inside a house and on telephones, evident during donner and blitzen, induction from a nearby ground strike can do it.  


Jaymack.

The deaths occurred over a period in winter so definitely not lightning related. My sole query is do you think that a voltage gradient could exist across A floor which had rubber coating. The cause of any voltage is secondary.

Are the slats supported on concrete sleeper walls or a steel frame?


Andy Betteridge

Slats supported on concrete sleeper walls which are re-enforced.

At the risk of stating the obvious, cow muck is likely to be reasonably conductive, not as good as salt water, but comparable to damp earth.

(and note that     manure has a high pH  here,   and  you can tell when soil was last manured by it's conductivity.)

Dry concrete is quite a good insulator at mains voltages, but as soon as it gets even slightly damp, less so.  If there was an external voltage gradient, from a buried faulty cable or fault running to a nearby earth terminal, then that voltage gradient could well appear in the building as well as outside. In some ways the slats make it more likely, as you can have one slat at a different potential to its neighbours.

However, gradients near electrodes tend to die out fast with distance - if you plant a vertical  electrode at 230V, and then stick your meter probes in nearby, such that you measure voltage to a fara way earth terminal, about half the voltage drop is within one electrode length of the top of the spike.

(If you wish to re-create this test, I strongly suggest not using full mains voltage, and not kneeling down to do the testing, and positioning the probes with it off, and then switching on from afar. )  My point is that within a few rod lengths away the surface voltage gradient has fallen to a safe level, so any such fault would have to be close.


Even though cattle have a long 'wheelbase' and are more sensitive to shock, they are not that sensitive, and the voltages likely to cause trouble are low but should be measurable on normal instruments.
Studies with current delivered from the mouth to hooves of dairy cattle in an environment which minimized contact resistance, indicated an avoidance reaction with currents of 1.0 to 4.0 ma AC. The same workers measured electrical resistance of dairy cows and determined an average value 390 ohms. Based on this work, it would appear that dairy cattle can "sense" currents of 1.0 to 6.0 ma AC and demonstrate a mild avoidance reaction at these levels. Using a 390 ohms resistance value, this translates to a threshold sensitivity of 0.4 to 2.4 volts.


from a Canadian paper   where common practice is to bring an earthed neutral to the barn - PME-like.


They eventually conclude that once NE voltage is < 1V there is no issue, and up to 5V most animals are not affected.

slightly lower thresholds are suggested here

I cannot distinguish if the purlins are timber or steel, the rest of the frame is steel. I am assuming that the frame is electrically conductive from one end of the building to the other.


It seems more likely to me that an animal was having a good rub against a steel stanchion with its four feet on the steel slat floor and an electrical fault at high level, perhaps on the lighting circuit, livened up the steel frame and its stanchions, rather than the floor becoming live.


You could make up a timber frame with four nails in it spaced as the animals feet are, then position it on the floor to take various test readings between the nails and also between them and the stanchions to establish what voltage gradient may exist between the stanchions and the floor if there is 240 volts on the steel frame, also across the floor in various locations. First off you need to determine what you need to know to know which tester to use.


I would also have a look about the place for a dodgy extension lead that may have been rolled up and put away.


Andy Betteridge