Mystery as 2 horses killed in the paddock at Newbury Races, [ about 60 miles west of London, England], believed electrocuted.

http://www.telegraph.co.uk/sport/ho...n-parade-ring-believed-electrocuted.html

Wouldnt doubt me much if deliberate.

Simple accident. Old u/g power cables, laid 30 years ago, probably pierced by a modern grass-aerating spiker machine.

http://www.telegraph.co.uk/news/ukn...er-horses-die-at-Newbury-racecourse.html

BTW, The reporter obviously thinks alumin[i]um does not conduct electricity!

Now that's some serious machinery!

And this just goes to show why underground cables in the UK are required to have steel wire armouring at earth-potential in them.
One of them spikes would have merely blown a fuse, alerting someone to the fact that the cable had been damaged in the first place.
Irregardless of the fact that the cable was laid far too shallow.

This is just one reason I will not run direct burial cable any more. Anything I put underground is in conduit, not only is it protected, but also repairable without digging.

Well since the incident happened in England this would mean the cable was not suitable for its use. An RCD, even if only 500mA would likely have prevented this though.

Is there a required minimal burial depth for underground cables in the UK? In all countries I know it's 60cm which isn't that far below the alleged 18-20" working range of the spikes.

Generally 45cm for domestic with a marker 15cm above it, or 60cm for other locations. Although all cables "shall be at sufficiant depth to avoid being damaged by any reasonably foreseeable distrubances to the ground"

That sort of machinery may not have been foreseeable when the cable was laid. Ground level may also have been changed since.....

I find it rather bizzare that you need such long spikes to aerate what is effectively a bit of lawn.
Now, I'm no gardener, but most of the aerater implements I've ever seen (that are pulled behind tractors) only have 100mm (4") spikes on them.

Even so, in the underground cables I've done in the past, you can't go past a few thin planks of treated timber over the top of the cable, irregardless of wether it is neutral-screened or armoured, these cables are made to be buried direct for those that are wondering.
Anything less should be in conduit anyway.

I've yet to see a slitter or hollow-tine grass aerator that would penetrate to the depth reported of 20". Grass is essentially shallow-rooted to perhaps 2" and such depths would be unnecessary. Most likely is the cable, reportedly laid 20 years ago, simply failed from a combination of rusty armoring, age and the forces associated with frost-heave. Southern England was uncharacteristically cold this winter [ to 3F ].

How does a four-legged animal get a shock - isn't grounding supposed to make things safe?

Exactly Alan,
I was going to add that fact to my post above about the roots of lawn-grass being shallow, but wasn't sure if I was right or not.

With respect to the cable in question, the PVC serving on the cable may have split some time ago, you don't know these things when a cable is buried in the ground, it also depends on how low the frost level there actually is.

Alan,
When a underground cable "faults", it can set up what is known as a voltage gradient on the ground above where the fault has occured.
Think of it as throwing a stone into a pond, the ripples that result are the currents "radiating" from the faulted cable.
If that fault does not "clear" (as in operating any protection like an RCD or a fuse/CB), it will cause a difference in potential between two given points on the ground.
Us humans are quite lucky, we only have 2 legs, but when you look at a quadruped like a horse, cat or dog, the chances of there being a greater difference in potential between the front and hind legs is increased.
Also, bear in mind that these animals never wear footwear like we do, a dog may feel a shock where we might not.
Finally, I think what has killed these animals is this, horses wear steel shoes (I've made them myself, my Grand-father was a Blacksmith).
Oddly enough I can't believe they're using aluminium shoes on horses, my Grand-father said (when he was still alive) that they could not adequately support the hooves of a horse and would lead to foot and leg problems.
The worst electric shock a human can get is a hand to hand shock, as it goes via the heart and as we all know the heart is run by electrical signals.
Quadrupeds that stand on the ground would have a situation of "Step Voltage" between each front foot, if there was enough of a potential difference (and current flow) between each front foot, you could kill an elephant, just because of the current running through the heart.

Freesat. A BBC West of England tv newscast today, midday GMT, veterinaries state that electrocution was the cause, not foul play, from a disused cable at least 20 years old. Southern Electric Distribution say area is now safe and cable has been disconnected and removed.

Video clip shows a few guys in SED yellow jackets near a shallow trench no more than 10" deep on the very edge of the paddock. One of them is winding loops of what looks like standard flexible 2.5mm? 1.6mm? pvc non-armored cable easily over his elbow and palm.

Update. National UK BBC News at Six this evening: Another short clip shows the cable to be no more than 8mm [ 5/16"] in diameter and obviously a flex.

So nothing done to any proper standard... even though I know of 40-year-old flex buried underground that's still in good-enough shape not to trip a 30mA RCD, even after winters with very heavy frosts.

Whenever I run underground cable, I cover the whole run with old bricks for good measure, just like I've seen workers do (mostly phone and cable TV).