ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

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/horsera...ectrocuted.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/uknews/8...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?