Horses Electrocuted at Newbury

JOHNPT

Two horses tragically died in the parade ring at Newbury yesterday. It is reported that probable cause was they died from some form of electric shock emanating from underneath the paddock. Has anybody any opinions on how and if this is possible?

Kristopherus

I thought the investigators had dismissed that idea.

Davy

An old cable running underneath apparently. Animals are more susceptible due to having 4 legs on the ground and the voltage difference between them does the damage. Its the voltage difference that kills you. Faraday cage principle, you can hold 500kv once you at the same potential, you are disconnected from earth. Cattle also suffer from this, and it can effect milk etc, causes mastitis

JOHNPT

How exactly does it occur as horses didnt touch cable as it was buried in the ground. If cable damaged should it not have tripped some fuse.

Bruthal

JOHNPT wrote: »

Two horses tragically died in the parade ring at Newbury yesterday. It is reported that probable cause was they died from some form of electric shock emanating from underneath the paddock. Has anybody any opinions on how and if this is possible?

Its possible if a phase(live) on a cable comes in contact with the earth as in the soil, and it forms a potential pool, and the voltage varies at different distances from it.

Horses and cattle having good contact with the ground with 4 feet and a good distance between front and back ones means they can have a good voltage difference or potential between their legs and makes them very vulnerable to electric shocks in such situations.

Bruthal

JOHNPT wrote: »

How exactly does it occur as horses didnt touch cable as it was buried in the ground. If cable damaged should it not have tripped some fuse.

Usually a single phase contact to the soil will not trip a breaker or blow a fuse on a mains cable of the phase is not in contact with steel armour or other solid earthed conductor. A few amps may flow to the earth but stays below the fuse rating. But 50 or 60ma, (0.05 to 0.06 amps is enough to kill a person, so a horse is probably around the same. But when the ground has a pontential on it, a horse with steel shoes and a firm connection to ground with 4 feet willl be in trouble, a person in their shoes and feet close together will probably notice little or nothing.

DublinDilbert

It would want to be a hv cable, either not in swa or the swa not grounded, to get any appreciable step voltage.

Ive heard it happening with earth faults on hv pylons.

Bruthal

I was thinking HV cable myself when i first heard of it, but horses are very sensitive to potential differences with the contact they have with the ground. At 230v the main thing that causes shocks for people to vary from mild to very severe is how good a contact we make at 2 points of the body. I know ESB 400v underground cables used to be just PVC PVC aluminium ones within housing estates etc, with no armour. Not sure these days what they use.

But a live cable or terminal could touch off a metal fence for example and leave a serious enough situation for horses. You just never know what sort of cable could of been run anywhere in the situation here.

Usually HV underground cables will trip on any sort of fault. HV overhead lines dont trip on earth faults so thats another point like you mention about the pylons.

But anyway HV was my own initial thought alright. But with horses and cattle 230v is dangerous. The horses may not have been killed as a result of electrocution anyway. Injuries from falling or panic and trying to stay on their feet would not be great for them.

Davy

DublinDilbert wrote: »

Ive heard it happening with earth faults on hv pylons.

With horses or what?

DublinDilbert

Davy wrote: »

With horses or what?

I've heard it happening to cows, that were in the same field as the pylon

Davy

DublinDilbert wrote: »

I've heard it happening to cows, that were in the same field as the pylon

Did they die? I presume it was just one phase made contact with the steel work some how.

flikasue

I if the ground was wet which I am sure it was and there was current this would act as a conductor and due to the fact the horses were wearing metal type shoes would not have helped.

If there is a lightening storm and you have horses with shoes on out in the field you should always bring them in because of the danger of being struck by lightening due to the shoes. A former employer of mine lost 4 horses in one go this way.

sparcocars

robbie7730 wrote: »

I know ESB 400v underground cables used to be just PVC PVC aluminium ones within housing estates etc, with no armour. Not sure these days what they use.
.

Still the same cable as that used. Just in a bed of sand and covered with marker boards. Some of really new estates have ducting so i suppose that would be supplementry armour.

cast_iron

The front of the today's Racing Post had this story. Apparently a cable has been dug up, and electrocution is pretty much confirmed.
Looks like maintenance on the irrigation system disrupted the cable somehow and led to the electrocution.

RoundyMooney

flikasue wrote: »

I if the ground was wet which I am sure it was and there was current this would act as a conductor and due to the fact the horses were wearing metal type shoes would not have helped.

If there is a lightening storm and you have horses with shoes on out in the field you should always bring them in because of the danger of being struck by lightening due to the shoes. A former employer of mine lost 4 horses in one go this way.

Wet ground will reduce the step voltage effect.

The wearing of shoes in the case of horses makes little difference, they have four parallel paths to earth anyway. Cattle and sheep are just as susceptible.

robbie7730 wrote: »

Usually a single phase contact to the soil will not trip a breaker or blow a fuse on a mains cable of the phase is not in contact with steel armour or other solid earthed conductor. A few amps may flow to the earth but stays below the fuse rating. But 50 or 60ma, (0.05 to 0.06 amps is enough to kill a person, so a horse is probably around the same. But when the ground has a pontential on it, a horse with steel shoes and a firm connection to ground with 4 feet willl be in trouble, a person in their shoes and feet close together will probably notice little or nothing.

And often on LV, it won't blow anything even if it is contacting the armour, or another phase. 30mA is considered the lethal level, hence the RCD rating. The biggest thing that works against our four legged friends is their weight, their length, and the fact that they don't wear soles! Horse shoes make no difference.

Davy wrote: »

Did they die? I presume it was just one phase made contact with the steel work some how.

Probably an MV earth fault, be it a lightning arrestor gone to earth, or a line down, 20kV MV will trip for earth faults, arc supression is used for higher voltages (a set inductance on the star point of the supplying transformer is used to negate the capacitance of the line-doesn't eliminate step voltage altogether of course!)

cast_iron wrote: »

The front of the today's Racing Post had this story. Apparently a cable has been dug up, and electrocution is pretty much confirmed.
Looks like maintenance on the irrigation system disrupted the cable somehow and led to the electrocution.

I believe so. I can assume this was an LV cable, as an MV cable would have more sophisticated protection. An LV cable will more often than not blow clear the fault, while the fuses behind it remain intact. A loss of phase or phases down stream is often the only indication.

Bruthal

RoundyMooney wrote: »

And often on LV, it won't blow anything even if it is contacting the armour,

Not with any good size fuses it wont anyway.
But an underground cable with a 20 amp breaker would still be capable of doing what happened, but would be less likely to blow through properly earthed steel armour in a fault. It would be interesting to know just what the cable was supplying.

Davy

RoundyMooney wrote: »

Probably an MV earth fault, be it a lightning arrestor gone to earth, or a line down, 20kV MV will trip for earth faults, arc supression is used for higher voltages (a set inductance on the star point of the supplying transformer is used to negate the capacitance of the line-doesn't eliminate step voltage altogether of course!)

I dont get ya, how is this effecting the HV pylon itself as per DD earlier post

Bruthal

RoundyMooney wrote: »

The biggest thing that works against our four legged friends is their weight, their length, and the fact that they don't wear soles! Horse shoes make no difference.

My point about the horses wearing steel shoes is when compared to us wearing synthetic insulating ones. Id say the fact horses have steel shoes held on with nails cant help their cause thats for sure, but the steel shoes just might make a better connection on firm but damp grass than a shoeless horse, as compared to a shoeless horse walking in a very muddy area. But overall in this situation shoes or no shoes would probably be of little difference alright. They might not of actually died directly of electrocution anyway, but of secondary effects, injury, panic etc.

With cattle, they are usually walking in well trampled muddy fields, or a soaking wet milking parlour in such situations compared to the horses paddock with clean firm grass, so thats another variation.

Wet ground will reduce the step voltage effect

Wet ground will reduce the step voltage effect alright, but improve the horses contact to it, so it would be hard to say what the overall effect would be between the two, a balance in the middle somewhere of worst effect. Bone dry summer ground and they probably would of felt nothing.

Bruthal

Davy wrote: »

I dont get ya, how is this effecting the HV pylon itself as per DD earlier post

Probably means a 10kv line earth fault and the line will remain live, although these days i think the phase with the fault is now earthed back at the feeding 38kv station to minimise the ground voltage effect at the fault. Lightning arrestors are the points of smallest gap from the lines to earth, so are likely spots for earth fault problems

20kv lines trip on earth faults. Do they stay out roundy, or try to automatically switch back in?

Higher voltage lines have an inductor between the star point and earth to reduce the capacitive effect of the line with the fault, as MV and HV lines have no solid link direct to earth as such and their interation with the ground is mostly through a capacitive effect between the phases and earth.
I still would not fancy standing near one of them though.

pieface_ie

How exactly does it occur as horses didnt touch cable as it was buried in the ground. If cable damaged should it not have tripped some fuse.

Legs spread out far apart will create a larger potential difference than legs close together.

RoundyMooney

robbie7730 wrote: »

Not with any good size fuses it wont anyway.
But an underground cable with a 20 amp breaker would still be capable of doing what happened, but would be less likely to blow through properly earthed steel armour in a fault. It would be interesting to know just what the cable was supplying.

Agreed. I look forward to the report myself.

robbie7730 wrote: »

With cattle, they are usually walking in well trampled muddy fields, or a soaking wet milking parlour in such situations compared to the horses paddock with clean firm grass, so thats another variation.

Wet ground will reduce the step voltage effect alright, but improve the horses contact to it, so it would be hard to say what the overall effect would be between the two, a balance in the middle somewhere of worst effect. Bone dry summer ground and they probably would of felt nothing.

Yep. Generally, dry ground is more dangerous the higher the voltage (and zone of influence though).

robbie7730 wrote: »

Probably means a 10kv line earth fault and the line will remain live, although these days i think the phase with the fault is now earthed back at the feeding 38kv station to minimise the ground voltage effect at the fault. Lightning arrestors are the points of smallest gap from the lines to earth, so are likely spots for earth fault problems

20kv lines trip on earth faults. Do they stay out roundy, or try to automatically switch back in?

Higher voltage lines have an inductor between the star point and earth to reduce the capacitive effect of the line with the fault, as MV and HV lines have no solid link direct to earth as such and their interation with the ground is mostly through a capacitive effect between the phases and earth.
I still would not fancy standing near one of them though.

This is why I like these discussions, it makes me think for the answers, even though I deal with this stuff all the time! I'll answer in order;

Yep, to clarify to others, ESB have two MV distribution voltages, 10 and 20kV. Both are somewhat different systems (if someone wants me to elaborate on this, no problem).

With 10kV, which came in with Siemens, from day one, the supply originates from a 110 or 38kV source (usually), via a wye/star secondary. The neutral doesn't do anything in this scenario, and in theory, should be at or near ground potential. Original system protection involved putting a voltage transformer on the neutral, so if one phase went to ground, the neutral voltage would rise (think of a triangle with a dot in the middle-each point is a phase, and the neutral voltage is the dot-earth one corner, and two things happen, the two other phases rise from 6.6kv to earth to 10kv, and the neutral also rises accordingly). This seldom blew a fuse, the system is isolated from earth, but all the lines above it make up a rather big capacitor, so fault current will flow, emanating out from ground in what's called the zone of influence. An animal or person within that will experience step voltage.

Anyway, the original VT was set to bring up an alarm if the neutral voltage exceeded 1.25kV, but that's all it did. The line or whatever, stayed on the ground burning away. Bear in mind, this was a different time.

The first solution was to measure line voltage to earth on each of the three phases in the station, and if an earth fault was detected, the lagging phase was earthed at the station, resulting in a short through the mass of earth (even if the fault was 20 miles away), and isolating the circuit.

The system that's in place now, in essence earths that phase itself back at the station, providing a much lower impedance parallel path for fault current to flow-bear in mind, any earth fault on a system like this consists of all the capacitive current on every line out of that station, and can be sizeable. This makes the fault site far safer, but doesn't mean someone can walk along and pick up the line (as has happened!)

So that's 10kV. Where cable comes into the equation, capacitive currents are far higher, as are the likelihood of digins, so earth fault tripping is generally used instead. No reclosing for earth faults is employed.

Now, 20kV (No prizes for guessing why the decision was taken to raise the distribution voltage). 20kV neutral is connected to earth via a 4ohm resistor, this is done to reduce the rise in line voltage when an earth fault occurs (see above), in order to allow compatibility with some of our older insulators etc. Generally, as a result, earth fault currents are far higher. Again, earth fault tripping is non reclose. However, where a high impedance earth fault occurs (like a hapless bird on a transformer), a time delay is used.

Other protection systems are being trialled for the 20kV system, but I may be crossing into the bounds of commercial sensitivity, so I can't say too much as yet

Bruthal

An underground MV cable system would probably be expected to trip on earth fault as well i would think, and not sustain a fault, they have a much higher capacitive effect because the cores are so close together so fault currents are higher, and also less likely to actually experience earth faults like overhead lines do, so not as prone to birds or tree branches etc causing nuisance faults.

Bruthal

RoundyMooney wrote: »

This is why I like these discussions, it makes me think for the answers, even though I deal with this stuff all the time! I'll answer in order;

Is just as well, as i forget most of it now at my age:D

ArseBurger

Davy wrote: »

Its the voltage difference that kills you.

No. It's current that kills you. Otherwise you'd kill yourself scratching your head or putting on a jumper.

And you might want to have a read up on Faraday's laws and the difference between his principle and his cage.

Bruthal

ArseBurger wrote: »

No. It's current that kills you. Otherwise you'd kill yourself scratching your head or putting on a jumper.

And you might want to have a read up on Faraday's laws and the difference between his principle and his cage.

You might want to read up on what governs the current magnitute in any circuit.

sparcocars

ArseBurger wrote: »

No. It's current that kills you. Otherwise you'd kill yourself scratching your head or putting on a jumper.

And you might want to have a read up on Faraday's laws and the difference between his principle and his cage.

Yes it is the current that kills you but essentially its the voltage that carries the current. People and animals have certain resistances to the flow of electricity.

Example : I might be able to touch 150 volts and not feel anything and someone else might be killed. (This is just a rough example)

With the horses front and back feet further apart than humans two feet are from each other the possible potential difference between them could be very different.

Example : Certain ground conditions above the location of a cable fault may cause the step voltages to be different. Imagine a 10 foot radius around the centre point of the fault and in one half the circle the ground is just slightly damp and the other half is dry. The step voltage in one side might be 50 volts and in the other side 150 volts. This would give the potential difference of 100 volts between the horses front legs and rear legs which would carry the current through the horse and give it a heart attack where as a human with feet closer together has a much smaller possibility of standing 1 foot on each side. And then the added protection of synthetic footwear on humans further decreases the risk. (Again just a rough example)