On Sun, 13 Feb 2011 12:51:15 -0800 (PST), zoe rothwell
wrote:

[...] My fear is that someone may have been using a taser or something
similar to strike the horses. A live cable would have affected the
grooms more (most only reported getting shocks off the horses, not the
grass), and the other horses when they walked over that part of the
paddock.

I searched for references to that possibility yesterday, when
this whole thing came up, but all I got were references to an
apparently famous champion horse named Taser Gun. :-(
--
Angus Rodgers

In article ,
zoe rothwell wrote:
[...]
Equines and electric;

As for the earlier comment on why it took so long for the horses to
die if it was electricity - electricity can stop the heart and can
interfere with the nervous system, but it is not always an immediate
effect of death. Potential difference across the heart can cause it
the fibrilate (flutter) or stop altogether, so the first doesn't kill
the animal for a very long time, if at all eg Kid Cassidy could have
been affected in this way. The second (heart stopping) is a slower way
of dying than you'd think - it's possible to have a human's heart stop
for several seconds at a time, many times a day as they age (in
certain heart conditions) and for the person not to die. Horses are on
a larger scale but I expect it works in the same way. So electrocution
is very much possible.

In both humans and horses, if the ventricles of the heart
fibrillate, they effectively stop pumping blood immediately,
cardiac output drops to zero (or near as damn it) and blood
pressure starts to plummet. Within a very few seconds in the case
of humans, brain function is depressed so much that consciousness
is lost and they keel over. A human heart stopping for as long
as several seconds would almost certainly result in fainting.
I have no reason to believe that it wouldn't be the same for
horses.

(At what point the person actually dies, assuming the heart
doesn't resume normal beating, is hard to say and is somewhat
academic.)

Francis

Martin wrote:

Me 9 wrote:

Greenaum wrote:

Bloke on news said the cable'd been untouched for at least 30 years. I
suppose maybe the insulation could've worn down. It's interesting to
see posts from people who know about this sort of thing, something you
never get on the news.

Probably aluminium cable from the 70s. Corroded badly by now.

On BBC R4 this morning they said the cable was 40 years old. It has aged
ten years since the BBC TV news yesterday.

We are now in the 2010s - 40 years later than the 1970s.


Fliss

--
She said: If you're an alien, why do you
sound like you're from the north?
He said: Lots of planets have a north.

Andrew wrote:

Nearly all animals need far fewer "mills that kills" (current)
through them to electrcute them than humans do. I don't know if
it is known why humans are more resistant to electrocution than
most other species, but I don't think the 6 or so generations
since the widespread use of electricity is long enough for
darwinism to be a factor, unless there had been an electrocution
pandemic, whereas it's actually very rare.

Anyone electrocuted before they breed is weeded out of the gene
pool, but I agree that would make only a marginal difference.

BTW, the word 'electrocution' is short for electric execution but
these are accidental deaths; however, I guess that's preferable
to the media using it to mean any (survivable) electric shock.

And 'pandemic' just means a disease unconfined to one location, it
doesn't mean the disease is deadly or that large numbers have been
infected; another word which is wilfully misused by the media.


Most humans will have experienced an electric shock, know what
it is, and know what to do to stop it. None of that is true of
most animals, and as I said before, when an animal is being
electrocuted by the ground, it can't "let go".

Hmm, perhaps we should shock toddlers, to train them...


When you have current leaking through the ground, it causes a
voltage difference across the ground. Let's say we're standing
on a piece of ground which has a voltage difference of 10V/foot.
Your feet are probably about a foot apart, and even with bare feet,
you wouldn't even feel 10V. Even if you did, the current path (up
one leg and down the other) isn't going to kill you. A horses feet
might be 6' apart, so it's going to have 60V across it. Futhermore,
that will be across the chest (heart, lungs) and much more
debilitating. Metal shoes will make better ground contact, pressing
right into the damp soil, although it's a very serious problem for
unshoed livestock too.

In that case, what voltage *would* it take to kill a human, when the
current passes through each leg and not across the chest?


Fliss

--
She said: Get up! Get up! Get up! God damn it! Get up, get
up, get up, get up, get up!! What is that noise?
He said: It's the chick! She's- going through some changes.

In article o.uk,
"Dave Liquorice" writes:
On Sun, 13 Feb 2011 18:48:58 +0000, Mike Tomlinson wrote:
Hope we find out. Interesting lesson if nothing else.

As with most things the media will have got bored with the story by
the time anything definite is discovered/worked out and the coverage
will be minimal.

It said on Radio 4 news today that a section of underground cable
has been removed and taken away for testing.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Felicity S." Fliss@orpheusnet wrote in message
news:fIxm7.2485$lk6.889132@orpheusnews...

BTW, the word 'electrocution' is short for electric execution but
these are accidental deaths; however, I guess that's preferable
to the media using it to mean any (survivable) electric shock.

http://dictionary.reference.com/browse/electrocute gives both meanings of
the word: execution by electricity being the original meaning (1889) but in
the sense of accidental death due to electricity, it was first recorded in
1909.

Similarly, New Oxford Dictionary of English, OUP, 2001 says "injure or kill
someone by electric shock: [example] a man was electrocuted on the rail
track", implying accidental death rather than execution.

"Mortimer" wrote in message
o.uk...
"Felicity S." Fliss@orpheusnet wrote in message
news:fIxm7.2485$lk6.889132@orpheusnews...

BTW, the word 'electrocution' is short for electric execution but
these are accidental deaths; however, I guess that's preferable
to the media using it to mean any (survivable) electric shock.

http://dictionary.reference.com/browse/electrocute gives both meanings of
the word: execution by electricity being the original meaning (1889) but
in the sense of accidental death due to electricity, it was first recorded
in 1909.

Similarly, New Oxford Dictionary of English, OUP, 2001 says "injure or
kill someone by electric shock: [example] a man was electrocuted on the
rail track", implying accidental death rather than execution.

By the way, the prize for unintentionally crass comment (quoted in
http://www.dailymail.co.uk/news/arti...ion-fears.html)
goes to Marching Song's part-owner Graham Thorner who said the fallen horse
had 'great potential'. ;-)

On Sun, 13 Feb 2011 12:51:15 -0800 (PST), zoe rothwell wrote:

A live cable would have affected the grooms more (most only reported
getting shocks off the horses, not the grass), ...

But would almost certainly be wearing rubber wellies, not steel shod
feet directly on the wet grass like the horses.

--
Cheers
Dave.

On 2/13/2011 7:42 PM, John Williamson wrote:
ARWadsworth wrote:
harry wrote:
On Feb 13, 1:44 pm, wrote:
On Sun, 13 Feb 2011 12:17:22 +0000, Angus Rodgers

wrote:
On Sun, 13 Feb 2011 10:06:35 -0000, "ARWadsworth"
wrote:
A quote from the DailyMail....
Marching Song's part-owner Graham Thorner said the fallen horse
had 'great potential'.
http://www.dailymail.co.uk/news/arti...s-fall-dead-Ne...

I don't like to joke about it, but: was this in the current affairs
section?
Shocking!
Now let's get more down to earth on this matter!

Apparently they died on the Ohm run.

I've been resisting the temptation to join in.

As long as you have enough resistance you'll be OK

harry wrote:
On Feb 13, 9:57 am, (Andrew Gabriel)
wrote:
In article ,
Donwill writes:





On 2/13/2011 4:05 AM, Mike Tomlinson wrote:
In , The Medway Handyman
writes
Could you expand on why horses are more susceptible than humans please
Andrew?
They're big animals, so more of a potential difference (a larger
voltage, in other words) appears between the front and hind legs. The
current then travels through the body via the heart. Result: dogmeat.
A human standing on the same ground only has the p.d. developed between
their feet. And humans don't as a rule wear shoes with metal soles.
I don't doubt you, but one would think a huge great horse would be more
resistant?
"it's the volts that jolts, but the mills that kills"
Nearly all animals need far fewer "mills that kills" (current)
through them to electrcute them than humans do. I don't know if
it is known why humans are more resistant to electrocution than
most other species, but I don't think the 6 or so generations
since the widespread use of electricity is long enough for
darwinism to be a factor, unless there had been an electrocution
pandemic, whereas it's actually very rare.

Most humans will have experienced an electric shock, know what
it is, and know what to do to stop it. None of that is true of
most animals, and as I said before, when an animal is being
electrocuted by the ground, it can't "let go".

When you have current leaking through the ground, it causes a
voltage difference across the ground. Let's say we're standing
on a piece of ground which has a voltage difference of 10V/foot.
Your feet are probably about a foot apart, and even with bare feet,
you wouldn't even feel 10V. Even if you did, the current path (up
one leg and down the other) isn't going to kill you. A horses feet
might be 6' apart, so it's going to have 60V across it. Futhermore,
that will be across the chest (heart, lungs) and much more
debilitating. Metal shoes will make better ground contact, pressing
right into the damp soil, although it's a very serious problem for
unshoed livestock too.

I would have thought that any 3ph 440V and upward cable underground
should be armoured and the armour sheathing earthed. Any leakage should
have tripped a breaker somewhere unless someone has been fiddling/
botching to get the race going. I wonder if we get any info on what
caused it ? (Cynic Mode switched on)
Mains supply cables don't have earth leakage detection. (Some higher
voltage supply cables do.) I don't know if all old cables had a
full metalic sheath. SWA (Steel wire armoured) cables are liable
to the steel rusting away if the outer sheath gets damaged, and
we've heard the race course suggest any cable must be 40 years old
(although that's not old for an underground cable).

Modern high voltage cables are normally singles and can't use steel
armour (unbalanced magnetic field from a single cable), so the
protection is copper, but it's rather more there to guarantee a
short to earth if the cable is damaged, than it is for mechanical
protection. Mechanical protection is provided by very tough plastic
coverings.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]- Hide quoted text -

- Show quoted text -

Nah. I have helped install many three phase three core 11Kv
underground cables. But they have always been at four feet deep at
least and tiled, labelled and really well protected. The danger is so
obvious. Only machine digging by a blind man could damage them.
The business is baffling.

well the one hey put outside MY house must have been installed by you,
cos it went bang.

Sme twit had backfilled it with sharp stones and the first lorry that
used tat pat of the verge as a passing place..

However, outside 240V cables do not have to be laid to such depths, and
indeed an idiot of a digger driver managed to cut that one up too.

Dave Liquorice wrote:
On Sun, 13 Feb 2011 12:51:15 -0800 (PST), zoe rothwell wrote:

A live cable would have affected the grooms more (most only reported
getting shocks off the horses, not the grass), ...

But would almost certainly be wearing rubber wellies, not steel shod
feet directly on the wet grass like the horses.

Titanium shoes on race horses I think.

Mike Tomlinson wrote:
In article , The Medway Handyman
writes

Could you expand on why horses are more susceptible than humans
please Andrew?

They're big animals, so more of a potential difference (a larger
voltage, in other words) appears between the front and hind legs. The
current then travels through the body via the heart. Result: dogmeat.

A human standing on the same ground only has the p.d. developed
between their feet. And humans don't as a rule wear shoes with metal
soles.


The Sun has a theory.

http://www.thesun.co.uk/sol/homepage...ctrocuted.html


Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

--
Adam

On Mon, 14 Feb 2011 02:06:42 -0000, "Mortimer"
wrote:

By the way, the prize for unintentionally crass comment (quoted in
http://www.dailymail.co.uk/news/arti...ion-fears.html)
goes to Marching Song's part-owner Graham Thorner who said the fallen horse
had 'great potential'. ;-)

I'm ashamed to admit that we've been cheerfully piling on the
crassness in another part of this thread. :-/
--
Angus Rodgers

In article ,
"ARWadsworth" writes:
Mike Tomlinson wrote:
In article , The Medway Handyman
writes

Could you expand on why horses are more susceptible than humans
please Andrew?

They're big animals, so more of a potential difference (a larger
voltage, in other words) appears between the front and hind legs. The
current then travels through the body via the heart. Result: dogmeat.

A human standing on the same ground only has the p.d. developed
between their feet. And humans don't as a rule wear shoes with metal
soles.


The Sun has a theory.

http://www.thesun.co.uk/sol/homepage...ctrocuted.html


Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Aluminium oxide is both an excellent insulator, and very hard.

Whilst breadboarding a circuit which used power MOSFETs to switch
mains, I temporarily clamped the two MOSFETs to the same aluminium
heatsink with a pair of bulldog clips. I knew it was live (didn't
bother with insulating kits whilst breadboarding), so kept clear
of it when powered up.

When recovering the components to build the final thing, it only
then dawned on me that the two MOSFET tabs had mains voltage
between them. The layer of aluminium oxide on the heatsinks had
withstood that, keeping the tabs insulated from the heatsinks
(well, at least one of them had, and possibly both), or there
would have been a big bang and fried MOSFETs.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

ARWadsworth wrote:
Mike Tomlinson wrote:
In article , The Medway Handyman
writes

Could you expand on why horses are more susceptible than humans
please Andrew?
They're big animals, so more of a potential difference (a larger
voltage, in other words) appears between the front and hind legs. The
current then travels through the body via the heart. Result: dogmeat.

A human standing on the same ground only has the p.d. developed
between their feet. And humans don't as a rule wear shoes with metal
soles.


The Sun has a theory.

http://www.thesun.co.uk/sol/homepage...ctrocuted.html


Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Perhaps it was a magnetic field inducing currents in the iron, but not
the al :-)

ARWadsworth wrote:

Mike Tomlinson wrote:

The Medway Handyman wrote:

Could you expand on why horses are more susceptible than humans
please Andrew?

They're big animals, so more of a potential difference (a larger
voltage, in other words) appears between the front and hind legs. The
current then travels through the body via the heart. Result: dogmeat.

A human standing on the same ground only has the p.d. developed
between their feet. And humans don't as a rule wear shoes with metal
soles.

The Sun has a theory. Quote "The two which died were shod in steel
whilst the survivors were wearing less-conductive aluminium."

My theory is the two which died stood facing towards or away from the
power line; the survivors stood more-or-less parallel, so electrically
each animal was a pair of bipeds with little current in the torso.


Fliss

--
He said: You gotta fight fire with fire, spread around a raunchy nickname
for her. What's that girl's name again? He said: Regina Tucker.
He said: Don't worry. We'll think of something.

Martin wrote:

Felicity S. wrote:
Martin wrote:
Me 9 wrote:
Greenaum wrote:

Bloke on news said the cable'd been untouched for at least 30
years.I suppose maybe the insulation could've worn down. It's
interesting to see posts from people who know about this sort of
thing, something you never get on the news.

Probably aluminium cable from the 70s. Corroded badly by now.

On BBC R4 this morning they said the cable was 40 years old. It has
aged ten years since the BBC TV news yesterday.

We are now in the 2010s - 40 years later than the 1970s.

FFS why did nobody tell me? Did you actually read what I wrote?

Yes, of course. I also read what Greenaum wrote.


Fliss

--
She said: You're going stay here with your
ex-wife because her sheep's dying?
He said: No, because *our* sheep's dying...

In article fIxm7.2485$lk6.889133@orpheusnews, Fliss@orpheusnet says...
My theory is the two which died stood facing towards or away from the
power line; the survivors stood more-or-less parallel, so electrically
each animal was a pair of bipeds with little current in the torso.

Nah - it's ley-lines, innit. The whole area's lousy with 'em. Probably
find they got tangled up in the exotic energy field that surrounds the
course.

Proper tin-foil hats (and in their cases skid-trays) and they'd have
been fine.

--
Skipweasel - never knowingly understood.

"greenaum" wrote in message
...
If it was a nobbling, probably the best way of finding out would be
traditional detective work. Trace who was betting on what, the horses'
owners, etc etc. Still, I think a freak accident is much more likely.
Who was it said something about not blaming things on malice that
could be put down to simple incompetence?

Sounds like an ideal investigation job for Dick Francis's Sid Halley!

On Tue, 15 Feb 2011 14:06:04 -0000, "Mortimer" wrote:

"greenaum" wrote in message
...
If it was a nobbling, probably the best way of finding out would be
traditional detective work. Trace who was betting on what, the horses'
owners, etc etc. Still, I think a freak accident is much more likely.
Who was it said something about not blaming things on malice that
could be put down to simple incompetence?

Some malicious person, probably.

Sounds like an ideal investigation job for Dick Francis's Sid Halley!

As it involves following the money trail, I was thinking of Detective
Lester Freamon from /The Wire/ - but we don't want any more bad puns.
--
Angus Rodgers

In article ,
Tim Streater wrote:
Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Aluminium oxide is both an excellent insulator, and very hard.

[snip war story]

While this is true, I would have expected that aly shoes would be
constantly being scratched, thus exposing fresh aly and allowing current
to pass.

I know the fresh aly oxidises fairly quickly but I don't know the
timescale.

Apparently some racing plates are made of anodized aluminium,
which is definitely harder to make conductive. I just tried
using the sharp probes on my multimeter on a piece of anodized
Al - no current. In contrast, I could get close to a zero ohm
reading from a sheet of ordinary aluminium with just touching
the probes on to the surface.

Francis

"greenaum" wrote in message
...
I imagine in your MOSFET case,
either one of them wasn't making proper contact or, more likely, the
FETs were tougher than you thought. Electronics, and power electronics
particularly, can take a lot more than they're rated for, before they
actually blow.

But when they blow, you know about it...

At university we had a project to develop a switched-mode power-supply in
which a thyristor is switched on and off at a constant frequency but with a
variable mark-to-space ratio to keep the output voltage after smoothing
constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated to
carry a certain current, but only when it was being switched and not when it
was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire
between the thryristor and the switching circuit while the PSU was carrying
full load...

Within a matter of about two seconds, there were five distinct sounds: a cry
of "****!" from the person who had accidentally disconnected the oscillator,
a yell of "duck!", a scraping of chairs on the floor as everyone took cover,
a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted
to the bang.

The end had blown off the thyristor and embedded itself in the ceiling -
thank goodness it went upwards instead of into someone.

In article , Francis Burton
scribeth thus
In article ,
Tim Streater wrote:
Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Aluminium oxide is both an excellent insulator, and very hard.

[snip war story]

While this is true, I would have expected that aly shoes would be
constantly being scratched, thus exposing fresh aly and allowing current
to pass.

I know the fresh aly oxidises fairly quickly but I don't know the
timescale.

Apparently some racing plates are made of anodized aluminium,
which is definitely harder to make conductive. I just tried
using the sharp probes on my multimeter on a piece of anodized
Al - no current. In contrast, I could get close to a zero ohm
reading from a sheet of ordinary aluminium with just touching
the probes on to the surface.

Francis

And I wonder what do they hold the Ally hoss shoes on with then?..
--
Tony Sayer

In article , Mortimer
scribeth thus
"greenaum" wrote in message
...
I imagine in your MOSFET case,
either one of them wasn't making proper contact or, more likely, the
FETs were tougher than you thought. Electronics, and power electronics
particularly, can take a lot more than they're rated for, before they
actually blow.

But when they blow, you know about it...

At university we had a project to develop a switched-mode power-supply in
which a thyristor is switched on and off at a constant frequency but with a
variable mark-to-space ratio to keep the output voltage after smoothing
constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated to
carry a certain current, but only when it was being switched and not when it
was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire
between the thryristor and the switching circuit while the PSU was carrying
full load...

Within a matter of about two seconds, there were five distinct sounds: a cry
of "****!" from the person who had accidentally disconnected the oscillator,
a yell of "duck!", a scraping of chairs on the floor as everyone took cover,
a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted
to the bang.

The end had blown off the thyristor and embedded itself in the ceiling -
thank goodness it went upwards instead of into someone.


Suppose thats what Uni us for, learning what to do when it all goes tits up..
--
Tony Sayer

"tony sayer" wrote in message
...
In article , Mortimer
scribeth thus
"greenaum" wrote in message
...
I imagine in your MOSFET case,
either one of them wasn't making proper contact or, more likely, the
FETs were tougher than you thought. Electronics, and power electronics
particularly, can take a lot more than they're rated for, before they
actually blow.

But when they blow, you know about it...

At university we had a project to develop a switched-mode power-supply in
which a thyristor is switched on and off at a constant frequency but with
a
variable mark-to-space ratio to keep the output voltage after smoothing
constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated
to
carry a certain current, but only when it was being switched and not when
it
was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire
between the thryristor and the switching circuit while the PSU was
carrying
full load...

Within a matter of about two seconds, there were five distinct sounds: a
cry
of "****!" from the person who had accidentally disconnected the
oscillator,
a yell of "duck!", a scraping of chairs on the floor as everyone took
cover,
a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted
to the bang.

The end had blown off the thyristor and embedded itself in the ceiling -
thank goodness it went upwards instead of into someone.


Suppose thats what Uni us for, learning what to do when it all goes tits
up..

I was very proud to be a member of the winning team who managed not to blow
their thyristor up and achieved staggeringly high efficiency measurements
(power out/power in) due to a novel design which a mate dreamed up. I've
still got the book that I received as a prize.

Talking of tits, if that thryistor had gone sideways, that's where it might
have ended up - in the Massive Mammaries (TM) of the only woman on the
course. ;-)

On 2011\02\15 16:58, greenaum wrote:
On Mon, 14 Feb 2011 15:03:04 +0000 (UTC),
(Andrew Gabriel) sprachen:

Aluminium oxide is both an excellent insulator, and very hard.

The tiny thin layer of it on aluminium is. But you can still conduct
current easily through aluminium foil, or metal. The oxide layer in
practice is too thin to insulate electrically.

The layer of oxide forms in just a few seconds on pure aluminium. I've
seen it happen on TV, it forms before one's very eyes. Same as when
you slice through Sodium.

It's too thin to make a difference. I imagine in your MOSFET case,
either one of them wasn't making proper contact or, more likely, the
FETs were tougher than you thought. Electronics, and power electronics
particularly, can take a lot more than they're rated for, before they
actually blow.

The current rails in third rail railway systems are nowadays made of
aluminium, so the insulating effect of the oxide layer is not important.

"tony sayer" wrote in message ...
In article , Francis Burton
scribeth thus
In article ,
Tim Streater wrote:
Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity values.

Aluminium oxide is both an excellent insulator, and very hard.

[snip war story]

While this is true, I would have expected that aly shoes would be
constantly being scratched, thus exposing fresh aly and allowing current
to pass.

I know the fresh aly oxidises fairly quickly but I don't know the
timescale.

Apparently some racing plates are made of anodized aluminium,
which is definitely harder to make conductive. I just tried
using the sharp probes on my multimeter on a piece of anodized
Al - no current. In contrast, I could get close to a zero ohm
reading from a sheet of ordinary aluminium with just touching
the probes on to the surface.

Francis

And I wonder what do they hold the Ally hoss shoes on with then?..

Glue?

Tim

Greenaum wrote:

Felicity S. wrote:

The Sun has a theory. Quote "The two which died were shod in steel
whilst the survivors were wearing less-conductive aluminium."

My theory is the two which died stood facing towards or away from the
power line; the survivors stood more-or-less parallel, so electrically
each animal was a pair of bipeds with little current in the torso.

You could be right. It's about volts-per-metre in this sort of
scenario.

That is so, thanks again to Andrew for the information.


Aluminium has virtually the same conductivity as steel, particularly
when compared to dirt and horseflesh. Stupid Sun. Who told them they
could have an opinion.

Yeah, though to be fair, the rest of the media are pretty daft too.


Fliss

--
He said: You guys need anything?
She said: Yes, a tear in the space-time continuum
so he can go back and say 'I love you'.

On 16/02/2011 01:00, John Rumm wrote:

Closely followed by an article on unexplained power cuts in a near by
village? ;-)

:-)

Meanwhile the following, posted in the IET wiring regs forum sheds some
light, and raises the question of why a long-disused cable was still
energised...

"A statement from Newbury said the racecourse was waiting for the
outcome of Southern Electric's investigations, but managing director
Stephen Higgins confirmed the likeliest possibility was the disused
cable had been damaged, possibly by recent verti-draining, a turf
maintenance procedure where spikes up to 18 inches long are used to
aerate the soil and reduce compaction."

"Higgins said: "We've looked at drawings that are 40 years old and we've
established that, before the 1992 grandstand was constructed, there was
a cable potentially in that location."

--
Andy

"greenaum" wrote in message
...
On Tue, 15 Feb 2011 18:06:00 -0000, "Mortimer"
sprachen:

I was very proud to be a member of the winning team who managed not to
blow
their thyristor up

Was that one of the initial criteria?

I ask because it seems pretty stupid using such a marginally specced
component. Surely variable mark/space includes 100:0. Even 95:5 must
have been pushing it for the component.

Also... don't thyristors stay switched on as long as they have enough
voltage across them? Or was it AC flowing through them? I'm sure
you'll have known this at the time, but wouldn't a simple transistor /
FET have been better?

You've got me wondering now: was it a thyristor or a FET? Not su it was
about 25 years ago and I can't remember. I agree: it was stupid to be given
a device that was specced right on the borderline and which wasn't tolerant
of error conditions such as under-spec input voltage, over-spec load current
or failure of the switching circuit. I dare say we could have built in extra
protection into the design, but I remember that component cost was one of
the design criteria.

greenaum wrote:
On Tue, 15 Feb 2011 18:06:00 -0000, "Mortimer"
sprachen:

I was very proud to be a member of the winning team who managed not to blow
their thyristor up

Was that one of the initial criteria?

I ask because it seems pretty stupid using such a marginally specced
component. Surely variable mark/space includes 100:0. Even 95:5 must
have been pushing it for the component.


Depends. If its feeding a transformer then you cant got to 100% as
there is then no AC.


You might well be modulating over a much narrower band of mark/space ratios.


Also... don't thyristors stay switched on as long as they have enough
voltage across them? Or was it AC flowing through them? I'm sure
you'll have known this at the time, but wouldn't a simple transistor /
FET have been better?


That's why it sounds like it might be an inductive load,

Mortimer wrote:

At university we had a project to develop a switched-mode power-supply in
which a thyristor is switched on and off at a constant frequency but with a
variable mark-to-space ratio to keep the output voltage after smoothing
constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated to
carry a certain current, but only when it was being switched and not when it
was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire
between the thryristor and the switching circuit while the PSU was carrying
full load...

Within a matter of about two seconds, there were five distinct sounds: a cry
of "****!" from the person who had accidentally disconnected the oscillator,
a yell of "duck!", a scraping of chairs on the floor as everyone took cover,
a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted
to the bang.

The end had blown off the thyristor and embedded itself in the ceiling -
thank goodness it went upwards instead of into someone.

I remember once reading a test report written by one of my
colleagues.

They had built a prototype railway rolling stock dc chopper based
on a string of thyristors. The assembly was placed on a
substantial metal bedplate in the test area. It was connected to
the power supply through a water fuse. This consisted of a
plastic bucket filled with water, having a couple of submerged
cable connectors and a thin wire between them. For safety, the
bucket had a wooden lid with a heavy weight sitting on it.

When the inevitable fault occurred, the fuse blew with some
force, creating a waterspout which lifted the lid high in the
air. Unfortunately, on the way back down, the heavy weight was
faster then the wooden lid, and it wedged itself between the
cable connectors, re-making the circuit. This would have been bad
enough on its own, but with all the water sloshing around on the
bedplate, the supply was now both shorted and earthed.

I believe it took some time to get supplies restored, and there
were no intact thyristors left.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

"Chris J Dixon" wrote in message
...
Mortimer wrote:

At university we had a project to develop a switched-mode power-supply in
which a thyristor is switched on and off at a constant frequency but with
a
variable mark-to-space ratio to keep the output voltage after smoothing
constant with a varying load.

We were warned that the thyristor that we'd been supplied with was rated
to
carry a certain current, but only when it was being switched and not when
it
was permanently turned on.

It was only a matter of time before one of the teams suffered a loose wire
between the thryristor and the switching circuit while the PSU was
carrying
full load...

Within a matter of about two seconds, there were five distinct sounds: a
cry
of "****!" from the person who had accidentally disconnected the
oscillator,
a yell of "duck!", a scraping of chairs on the floor as everyone took
cover,
a VERY loud bang like a shotgun, and a gasp of "F**k!" as everyone reacted
to the bang.

The end had blown off the thyristor and embedded itself in the ceiling -
thank goodness it went upwards instead of into someone.

I remember once reading a test report written by one of my
colleagues.

They had built a prototype railway rolling stock dc chopper based
on a string of thyristors. The assembly was placed on a
substantial metal bedplate in the test area. It was connected to
the power supply through a water fuse. This consisted of a
plastic bucket filled with water, having a couple of submerged
cable connectors and a thin wire between them. For safety, the
bucket had a wooden lid with a heavy weight sitting on it.

When the inevitable fault occurred, the fuse blew with some
force, creating a waterspout which lifted the lid high in the
air. Unfortunately, on the way back down, the heavy weight was
faster then the wooden lid, and it wedged itself between the
cable connectors, re-making the circuit. This would have been bad
enough on its own, but with all the water sloshing around on the
bedplate, the supply was now both shorted and earthed.

I believe it took some time to get supplies restored, and there
were no intact thyristors left.

Sounds like it was caused by the same Sods Law fairy that caused the chain
of events in Gerard Hoffnung's story about the barrel of bricks being
hoisted up the building.

The thought of water near an electrical installation sounds like an accident
waiting to happen...

In article , John
Rumm scribeth thus
On 13/02/2011 23:36, Felicity S. wrote:
Andrew wrote:

When you have current leaking through the ground, it causes a
voltage difference across the ground. Let's say we're standing
on a piece of ground which has a voltage difference of 10V/foot.
Your feet are probably about a foot apart, and even with bare feet,
you wouldn't even feel 10V. Even if you did, the current path (up
one leg and down the other) isn't going to kill you. A horses feet
might be 6' apart, so it's going to have 60V across it. Futhermore,
that will be across the chest (heart, lungs) and much more
debilitating. Metal shoes will make better ground contact, pressing
right into the damp soil, although it's a very serious problem for
unshoed livestock too.

In that case, what voltage *would* it take to kill a human, when the
current passes through each leg and not across the chest?

Voltage is a bit of a non issue in this case. Its the magnitude of the
current and duration that will largely dictate the level of injury along
with the general health and state of the victim. Obviously higher
voltages make it easier to push the current through the body, and high
enough ones make possible severe injury from follow on effects like arc
flash.




The volts is the most, or most important part as you can have Mega amps
at say 1 volt thats not, well unless its connected perhaps to electrodes
buried in the brain, going to have much effect through the average Joe
or Horsey.

Course you can have Mega Volts at a yoctoamp and thats not really going
to have an effect either..

The matter is a combination of volts, the current capacity of that
source. The Resistance of the connection to the victim and the
electrical source and the resistance of the victims skin and the path of
the current..

In the case of a Human from one leg to the other is less dangerous than
from hand to hand which has the Heart etc in the path.

Course sufficient volts across whatever member of the body can cause
debilitating effects and heating burning and possibly death...


It seems to me that in this case there must have been quite a voltage
gradient across that ground either from a source that had the "other
side" of itself earthed elsewhere, or possibly two conductors a distance
apart and the flow was across the ground. Course we'll see what the
official line is from those investigating..
--
Tony Sayer

In article , Tim Downie
scribeth thus

"tony sayer" wrote in message
o.uk...
In article , Francis Burton
scribeth thus
In article ,
Tim Streater wrote:
Quote "The two which died were shod in steel whilst the survivors were
wearing less-conductive aluminium."

I suspect that someone at The Sun does not understand conductivity
values.

Aluminium oxide is both an excellent insulator, and very hard.

[snip war story]

While this is true, I would have expected that aly shoes would be
constantly being scratched, thus exposing fresh aly and allowing current
to pass.

I know the fresh aly oxidises fairly quickly but I don't know the
timescale.

Apparently some racing plates are made of anodized aluminium,
which is definitely harder to make conductive. I just tried
using the sharp probes on my multimeter on a piece of anodized
Al - no current. In contrast, I could get close to a zero ohm
reading from a sheet of ordinary aluminium with just touching
the probes on to the surface.

Francis

And I wonder what do they hold the Ally hoss shoes on with then?..

Glue?

Tim


Not Steel nails then?..
--
Tony Sayer

Mortimer wrote:

"Chris J Dixon" wrote in message
.. .

I remember once reading a test report written by one of my
colleagues.

They had built a prototype railway rolling stock dc chopper based
on a string of thyristors. The assembly was placed on a
substantial metal bedplate in the test area. It was connected to
the power supply through a water fuse. This consisted of a
plastic bucket filled with water, having a couple of submerged
cable connectors and a thin wire between them. For safety, the
bucket had a wooden lid with a heavy weight sitting on it.

When the inevitable fault occurred, the fuse blew with some
force, creating a waterspout which lifted the lid high in the
air. Unfortunately, on the way back down, the heavy weight was
faster then the wooden lid, and it wedged itself between the
cable connectors, re-making the circuit. This would have been bad
enough on its own, but with all the water sloshing around on the
bedplate, the supply was now both shorted and earthed.

I believe it took some time to get supplies restored, and there
were no intact thyristors left.

Sounds like it was caused by the same Sods Law fairy that caused the chain
of events in Gerard Hoffnung's story about the barrel of bricks being
hoisted up the building.

The thought of water near an electrical installation sounds like an accident
waiting to happen...

Indeed, but the characteristics of a water fuse, crude though it
sounds, actually make it very good for semiconductor protection,
and a great deal cheaper than the equivalent cartridge fuse,
which could easily cost as much as the device it protected.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

tony sayer wrote:
In article , John
Rumm scribeth thus
On 13/02/2011 23:36, Felicity S. wrote:
Andrew wrote:
When you have current leaking through the ground, it causes a
voltage difference across the ground. Let's say we're standing
on a piece of ground which has a voltage difference of 10V/foot.
Your feet are probably about a foot apart, and even with bare feet,
you wouldn't even feel 10V. Even if you did, the current path (up
one leg and down the other) isn't going to kill you. A horses feet
might be 6' apart, so it's going to have 60V across it. Futhermore,
that will be across the chest (heart, lungs) and much more
debilitating. Metal shoes will make better ground contact, pressing
right into the damp soil, although it's a very serious problem for
unshoed livestock too.
In that case, what voltage *would* it take to kill a human, when the
current passes through each leg and not across the chest?
Voltage is a bit of a non issue in this case. Its the magnitude of the
current and duration that will largely dictate the level of injury along
with the general health and state of the victim. Obviously higher
voltages make it easier to push the current through the body, and high
enough ones make possible severe injury from follow on effects like arc
flash.




The volts is the most, or most important part as you can have Mega amps
at say 1 volt thats not, well unless its connected perhaps to electrodes
buried in the brain, going to have much effect through the average Joe
or Horsey.


Er no.

Beause of te resistane of te hman tuissues, there is an intrinsic
relationship beween the volts and maps.

The long and te short of it is that whilst internally teh volts make
lill and teh aps will burn, its the amps through that count, as these
deliver the volts to te tiossues.

DC amps tend to kill by burning, AC amps by heart stoppage.

You cant GET mega amps through the body without serious volts..


Course you can have Mega Volts at a yoctoamp and thats not really going
to have an effect either..

The matter is a combination of volts, the current capacity of that
source. The Resistance of the connection to the victim and the
electrical source and the resistance of the victims skin and the path of
the current..


Exactly.

In the case of a Human from one leg to the other is less dangerous than
from hand to hand which has the Heart etc in the path.


Ditto.

Course sufficient volts across whatever member of the body can cause
debilitating effects and heating burning and possibly death...


It seems to me that in this case there must have been quite a voltage
gradient across that ground either from a source that had the "other
side" of itself earthed elsewhere, or possibly two conductors a distance
apart and the flow was across the ground. Course we'll see what the
official line is from those investigating..

I would estimate 50-100 volts across the front hooves would stop a
racehorse dead in its tracks, if the ground was damp. The frog is fairly
sensitive a bit of skin. Lie the palms of yer hand..

In article , The Natural Philosopher
scribeth thus
tony sayer wrote:
In article , John
Rumm scribeth thus
On 13/02/2011 23:36, Felicity S. wrote:
Andrew wrote:
When you have current leaking through the ground, it causes a
voltage difference across the ground. Let's say we're standing
on a piece of ground which has a voltage difference of 10V/foot.
Your feet are probably about a foot apart, and even with bare feet,
you wouldn't even feel 10V. Even if you did, the current path (up
one leg and down the other) isn't going to kill you. A horses feet
might be 6' apart, so it's going to have 60V across it. Futhermore,
that will be across the chest (heart, lungs) and much more
debilitating. Metal shoes will make better ground contact, pressing
right into the damp soil, although it's a very serious problem for
unshoed livestock too.
In that case, what voltage *would* it take to kill a human, when the
current passes through each leg and not across the chest?
Voltage is a bit of a non issue in this case. Its the magnitude of the
current and duration that will largely dictate the level of injury along
with the general health and state of the victim. Obviously higher
voltages make it easier to push the current through the body, and high
enough ones make possible severe injury from follow on effects like arc
flash.




The volts is the most, or most important part as you can have Mega amps
at say 1 volt thats not, well unless its connected perhaps to electrodes
buried in the brain, going to have much effect through the average Joe
or Horsey.


Er no.

Beause of te resistane of te hman tuissues, there is an intrinsic
relationship beween the volts and maps.

The long and te short of it is that whilst internally teh volts make
lill and teh aps will burn, its the amps through that count, as these
deliver the volts to te tiossues.

Thats the same as what I wrote above!..


DC amps tend to kill by burning, AC amps by heart stoppage.


You've been reading too much Westinghouse -v- Edision;!..

You cant GET mega amps through the body without serious volts..

Yes as I said..


Any chance of a new spull chucker for the new year...



Course you can have Mega Volts at a yoctoamp and thats not really going
to have an effect either..

The matter is a combination of volts, the current capacity of that
source. The Resistance of the connection to the victim and the
electrical source and the resistance of the victims skin and the path of
the current..


Exactly.

In the case of a Human from one leg to the other is less dangerous than
from hand to hand which has the Heart etc in the path.


Ditto.

Course sufficient volts across whatever member of the body can cause
debilitating effects and heating burning and possibly death...


It seems to me that in this case there must have been quite a voltage
gradient across that ground either from a source that had the "other
side" of itself earthed elsewhere, or possibly two conductors a distance
apart and the flow was across the ground. Course we'll see what the
official line is from those investigating..

I would estimate 50-100 volts across the front hooves would stop a
racehorse dead in its tracks, if the ground was damp. The frog is fairly
sensitive a bit of skin. Lie the palms of yer hand..

Wonder if anyone did any research on that;?.

Not like poor old Topsy the elephant;(.
--
Tony Sayer

On 16/02/2011 15:10, John Rumm wrote:

It will be interesting to know if its on the supply side or the
consumers side. I suspect that there will be some recriminations if it
turns out to be on the racecourses side of the supply rather than
southern electric's.

Quite - and whoever left it live probably buggered off long ago...

--
Andy

On Feb 16, 10:58*pm, Andy Wade wrote:
On 16/02/2011 15:10, John Rumm wrote:

It will be interesting to know if its on the supply side or the
consumers side. I suspect that there will be some recriminations if it
turns out to be on the racecourses side of the supply rather than
southern electric's.

Quite - and whoever left it live probably buggered off long ago...

--
Andy

A recent episode of CSI Miami (made long before the Newbury horse
deaths) used an under beach cable to knock off (as in electrocute) a
mens volley ball team. One wonders where they got the idea from. Or
did reality copy fiction in this case.