On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

--
Graham.
%Profound_observation%

In article ,
lid says...

On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

Question - If the bird is in free space and then lands on the wire,
where is this current flowing through the bird, flowing too?

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

You could aways test the theory by touching the wire with the bird
sitting on it, making sure you are well earthed first of course. :-)

Yellow wrote:
In article ,
lid says...
Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

Question - If the bird is in free space and then lands on the wire,
where is this current flowing through the bird, flowing too?

The current flows in and out of the capacitance presented by the bird,
due to its mass. A few nanofarads at most, which at 50Hz gives a
negligible current. The bird is more likely to sense the alternating
magnetic field surrounding the wire, as experiments have shown that
some, if not all, birds can sense magnetic fields.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

You could aways test the theory by touching the wire with the bird
sitting on it, making sure you are well earthed first of course. :-)

The more likely explanation is that live cables are warmer than the
surrounding air, and the birds don't like having hot feet, or that the
magnetic field causes them discomfort or disorientation.

--
Tciao for Now!

John.

On Fri, 31 Aug 2012 23:33:50 +0100, John Williamson wrote:

I always assumed that's why you rarly see birds perching on the
actual phase wires, and when you do, they (the wires) are probebly
dead.

The more likely explanation is that live cables are warmer than the
surrounding air, and the birds don't like having hot feet, or that the
magnetic field causes them discomfort or disorientation.

Could be the magnetic field but also the size of the wire, even our lowly
single phase 11kV feed has wires about 1/2" dia. Pylon supported grid
cables are up to 2" or so in dia... Birds certainly perch on our
powerline at times but normally in a flock. Sat on a wire in free space
is a very exposed position for a tasty snack.

--
Cheers
Dave.

On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird will be
negligible - it will have a tiny capacitance.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird will be
negligible - it will have a tiny capacitance.


--
Cheers,

John.

/================================================== ===============\
|
Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internod
e(dot)co(dot)uk
But. Won't the bird experience the effect of the arc that
Will strike between it and the conductor as it approaches?
I should think that would be a deterrent. |
\================================================= ================/

On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it even
feels it at all - might enjoy having warm feet in winter though.

--
Regards,
Martin Brown

Martin Brown wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it even
feels it at all - might enjoy having warm feet in winter though.

Big bats have a problem,I used to get dead bats in the front of my
place,we had a lillypilly tree which bats like and I thought it must
poison them.
It turned out, when they left the tree their wingspan was big enough to
span the two phases on the aerials in the street.

On Aug 31, 10:35*pm, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop

wrote:
Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

--
Graham.
%Profound_observation%

I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

On 01/09/2012 09:29, F Murtz wrote:
Martin Brown wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it even
feels it at all - might enjoy having warm feet in winter though.

Big bats have a problem,I used to get dead bats in the front of my
place,we had a lillypilly tree which bats like and I thought it must
poison them.
It turned out, when they left the tree their wingspan was big enough to
span the two phases on the aerials in the street.

That is surprising. I once saw a flock of seagulls get into big trouble
with a 40kV thin wire line they didn't see and flew into it en mass and
at speed. It was pretty horrible with many injured seagulls flapping
around on the ground and an unlucky few hung up by a wing on the wires.

Arguably the poor things should have gone to specsavers in this case.

RSPCA had to come and do them in. Not sure how they resolved the ones on
the hot wire I think NEDL had to come and knock them off with some sort
of isolated broom handle. I didn't hang around for that bit.

It wasn't the electricity that harmed them though it was physically
hitting a strong thin wire at speed.

--
Regards,
Martin Brown

On Aug 31, 10:35*pm, Graham. wrote:


I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

Almost every day outside our house. In the evenings at certain times
of year there are literally hundreds.

Hardly "rarely".

MBQ

harry wrote:
On Aug 31, 10:35 pm, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop

wrote:
Deux set the following eddies spiralling through the space-time continuum:
http://www.specsavers.co.uk/2012-eye-test/birds/
Anyone notice anything wrong in that picture?
Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?
That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

--
Graham.
%Profound_observation%

I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I cant
swear to it because the nearest is a long way away.



--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

The Natural Philosopher wrote:
harry wrote:
On Aug 31, 10:35 pm, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop

wrote:
Deux set the following eddies spiralling through the space-time
continuum:
http://www.specsavers.co.uk/2012-eye-test/birds/
Anyone notice anything wrong in that picture?
Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?
That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

--
Graham.
%Profound_observation%

I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I cant
swear to it because the nearest is a long way away.



heres some good stuff

http://www.squidoo.com/why-birds-lik...on-power-lines


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

Haven't you ever seen men jumping onto HV cables from helicopters? They
have a lot more capacitance than a small bird. The birds will be fine

On 31 Aug, 23:17, Yellow wrote:
In article ,
says...







On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

Question - If the bird is in free space and then lands on the wire,
where is this current flowing through the bird, flowing too?

There are lots of interesting questions like that. It's not actually
necessary to complete a circuit with wires.

The presence of free space is sufficient to conduct electromagnetic
energy - that's why you can watch television, without having two wires
connected between the screen and your eyes. So too, it is why you can
receive a television signal using an aerial, which by definition does
not have a wired circuit to the transmitter.

Birds can and do perch on live high-voltage conductors. What happens
when they do so, is that they are "charged" more or less up to the
potential of the conductor. A very small amount of current will flow
into the bird, according to its electrical characteristics - and in
the case of AC, that current will continue to flow according to the
regular change in voltage (with DC, current would flow as the bird
charged, and then would drop to nothing).

In terms of "where does the current passing into the bird flow to",
the straightforward answer is nowhere, if the bird is insulated from
the conductor of the opposing voltage. In reality, there is no perfect
insulator, and a very tiny amount of current will flow around the
circuit and through the bird, but the bird is (usually) sufficiently
insulated that no harmful levels of power will pass.

I often find that the hydraulic analogy is very apt to demonstrate
this sort of thing. (Technically, and contrary to common
understanding, fluid also requires a circuit in order to flow
effectively, just as electricity - no fluid will flow between two
points in space, if there is no pressure difference between those
points or no flow path between those points). If you use a pump to
pressure a fluid in a dead-end pipe (the pipe being the hydraulic
equivalent to an electrical insulator), then even though there is no
immediate way for the fluid to escape, a small amount of fluid will
move away from the pump towards the end of the pipe furthest from the
pump, in order to equalise pressures throughout the fluid on that side
of the pump. If you then tap into this pipe along its length, adding
another tee piece (the bird), then fluid will also flow into the tee
piece until it is also charged to the same pressure as the whole pipe.

If the bird flies off the wire at the appropriate time (i.e. when the
AC voltage is not zero), for a period of time it will actually remain
charged at the high voltage, until inductance re-equalises the
potential difference between the bird and its surroundings (or until
it resettles on an earthed conductor).



I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

You could aways test the theory by touching the wire with the bird
sitting on it, making sure you are well earthed first of course. :-)

If one were "well-earthed", touching a live conductor is the last
thing one would want to do.

On Sat, 01 Sep 2012 11:57:39 +0100, Ste wrote:



If one were "well-earthed", touching a live conductor is the last
thing one would want to do.

Musicians know this. You often see the conductor kept well away from them,
often in a sort of metal 'cage'.

--
Rod

On Fri, 31 Aug 2012 22:35:14 +0100, Graham. wrote:

On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq
sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.


Is that so? What charge does a bird flying through dry air build-up? My
guess is that in some conditions a bird's potential might be higher than
that of the conductor they land on. Hence there would be an outflow rather
than an inflow. (Mind, are we talking electron flow, conventional current
flow?)

--
Rod

Martin Brown wrote:
On 01/09/2012 09:29, F Murtz wrote:
Martin Brown wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on
the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it
even
feels it at all - might enjoy having warm feet in winter though.

Big bats have a problem,I used to get dead bats in the front of my
place,we had a lillypilly tree which bats like and I thought it must
poison them.
It turned out, when they left the tree their wingspan was big enough to
span the two phases on the aerials in the street.

That is surprising. I once saw a flock of seagulls get into big trouble
with a 40kV thin wire line they didn't see and flew into it en mass and
at speed. It was pretty horrible with many injured seagulls flapping
around on the ground and an unlucky few hung up by a wing on the wires.

Arguably the poor things should have gone to specsavers in this case.

RSPCA had to come and do them in. Not sure how they resolved the ones on
the hot wire I think NEDL had to come and knock them off with some sort
of isolated broom handle. I didn't hang around for that bit.

It wasn't the electricity that harmed them though it was physically
hitting a strong thin wire at speed.

Our fruit bats have a wingspan of almost a metre (African ones up to 6
feet)

In article 025ba0e4-4b02-4279-867e-
, says...

On 31 Aug, 23:17, Yellow wrote:
In article ,
says...

You could aways test the theory by touching the wire with the bird
sitting on it, making sure you are well earthed first of course. :-)

If one were "well-earthed", touching a live conductor is the last
thing one would want to do.

No **** sherlock.

"The Natural Philosopher" wrote in message
...


I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I cant
swear to it because the nearest is a long way away.

Overhead lines can get hot under load.
You can hear the rain sizzle as it lands.
Birds aren't going to cook themselves.

On Sat, 01 Sep 2012 12:12:11 +0100, polygonum
wrote:

On Fri, 31 Aug 2012 22:35:14 +0100, Graham. wrote:

On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq
sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.


Is that so? What charge does a bird flying through dry air build-up? My
guess is that in some conditions a bird's potential might be higher than
that of the conductor they land on. Hence there would be an outflow rather
than an inflow. (Mind, are we talking electron flow, conventional current
flow?)

I've just had an idea for a renewable energy scheme....

Nick

"Martin" wrote in message
...

Haven't you ever seen men jumping onto HV cables from helicopters? They
have a lot more capacitance than a small bird. The birds will be fine

Yes.
They have a probe to bond the copter to the wire before the man gets killed
by the current going through him.
The current arcs across several inches as the probe is attached.

On 01/09/2012 06:52, Graham wrote:


John Rumm wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird will be
negligible - it will have a tiny capacitance.

But. Won't the bird experience the effect of the arc that
Will strike between it and the conductor as it approaches?
I should think that would be a deterrent.

Just what voltage do you suppose that fence is running at? (its purpose
being to discourage livestock from touching it, not toast it from a yard
away!)

(I now have a mental image if a Frankenstein's laboratory style
electrical setup, with electrical arcs climbing jacob's ladders etc)


--
Cheers,

John.

/================================================== ===============\
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On Sat, 01 Sep 2012 12:12:11 +0100, polygonum
wrote:

On Fri, 31 Aug 2012 22:35:14 +0100, Graham. wrote:

On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq
sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.


Is that so? What charge does a bird flying through dry air build-up? My
guess is that in some conditions a bird's potential might be higher than
that of the conductor they land on. Hence there would be an outflow rather
than an inflow.
Yes, I am sure that is right, just as vehicles and aircraft build up a
charge, or us walking on a nylon carpet and touching an electrically
floating metal handrail (which illustrates the point rather nicely.

(Mind, are we talking electron flow, conventional current
flow?)
Oh dear, have they still not that anomaly sorted out?

What I don't think is always helpful, is to think of "static"
electricity as somehow a different phenomenon to "ordinary" electric.
Is that how it is still presented in schools?

--
Graham.
%Profound_observation%

On 01/09/2012 09:44, Martin Brown wrote:
On 01/09/2012 09:29, F Murtz wrote:
Martin Brown wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on
the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it
even
feels it at all - might enjoy having warm feet in winter though.

Big bats have a problem,I used to get dead bats in the front of my
place,we had a lillypilly tree which bats like and I thought it must
poison them.
It turned out, when they left the tree their wingspan was big enough to
span the two phases on the aerials in the street.

That is surprising. I once saw a flock of seagulls get into big trouble
with a 40kV thin wire line they didn't see and flew into it en mass and
at speed. It was pretty horrible with many injured seagulls flapping
around on the ground and an unlucky few hung up by a wing on the wires.

Arguably the poor things should have gone to specsavers in this case.

Its early morning on the plain, and two vultures awake. The younger one
says

"I am going to go find me some blood. You coming?".

The older wiser bird says

"Na, you go, I am going to soak up the early morning sun for a bit,
anyway I doubt there are any good kills laying about for us yet".

So the young bird flies off by himself. After ten minutes he returns,
and to the wiser birds amazement he it absolutely covered it blood. Its
all over his feathers and literally dripping off his beak.

"Wow, said the bird on the tree, you must have found something *big"...
"what was it... a cow?"

"Na", says the bird...

"a buffalo?"

"Nope"

The bloodied bird says

"come with me and see".

So they both fly off together. After five minutes of flying the young
bid says

"You see that big old oak tree down there?".

The old bid excitedly says

"Yes, yes...".

The young bird replies

"Well I didn't!"


--
Cheers,

John.

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\================================================= ================/

On 01/09/2012 10:30, The Natural Philosopher wrote:
harry wrote:
On Aug 31, 10:35 pm, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop

wrote:
Deux set the following eddies spiralling through the space-time
continuum:
http://www.specsavers.co.uk/2012-eye-test/birds/
Anyone notice anything wrong in that picture?
Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?
That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

--
Graham.
%Profound_observation%

I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I cant
swear to it because the nearest is a long way away.

We have one near us, often gets flocks of starlings etc on it.


--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sat, 01 Sep 2012 13:57:06 +0100, John Rumm
wrote:

On 01/09/2012 06:52, Graham wrote:


John Rumm wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird will be
negligible - it will have a tiny capacitance.

But. Won't the bird experience the effect of the arc that
Will strike between it and the conductor as it approaches?
I should think that would be a deterrent.

Just what voltage do you suppose that fence is running at? (its purpose
being to discourage livestock from touching it, not toast it from a yard
away!)

(I now have a mental image if a Frankenstein's laboratory style
electrical setup, with electrical arcs climbing jacob's ladders etc)

Sorry John, I was posting in the middle of the night from my
crippleberry. I thought we were still talking about super-grid lines.
A spark must jump between the approaching object and the wire.

--
Graham.
%Profound_observation%

On 01/09/2012 13:27, dennis@home wrote:


"The Natural Philosopher" wrote in message
...


I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I
cant swear to it because the nearest is a long way away.

Overhead lines can get hot under load.
You can hear the rain sizzle as it lands.

The "sizzle" is more likely corona discharge.

Birds aren't going to cook themselves.

Which since you can't get flying chickens, is less of a downside than it
may first appear ;-)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

dennis@home wrote:


"The Natural Philosopher" wrote in message
...


I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I
cant swear to it because the nearest is a long way away.

Overhead lines can get hot under load.
You can hear the rain sizzle as it lands.

The sizzle is not from heat. Its corona discharge

IIRC the heat limits are in the 40-90C range. More than that and the
wires start to sag too much.

Remember that whiles the transmitted power is VI, the losses are I^2 R
so a small decrease in power is a BIG drop in temperature.

So most of the time the wires run pretty cool



Birds aren't going to cook themselves.

But they like warm feet.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Sat, 01 Sep 2012 14:03:31 +0100, Graham. wrote:


Yes, I am sure that is right, just as vehicles and aircraft build up a
charge, or us walking on a nylon carpet and touching an electrically
floating metal handrail (which illustrates the point rather nicely.

(Mind, are we talking electron flow, conventional current
flow?)
Oh dear, have they still not that anomaly sorted out?

What I don't think is always helpful, is to think of "static"
electricity as somehow a different phenomenon to "ordinary" electric.
Is that how it is still presented in schools?


Have not been into a school of any sort in many years. :-)

Absolutely agree about static versus, umm, dynamic (?) electricity.
Teaching did seem to make them seem like different beasts.

--
Rod

On 01/09/2012 14:11, Graham. wrote:
On Sat, 01 Sep 2012 13:57:06 +0100, John Rumm
wrote:

On 01/09/2012 06:52, Graham wrote:


John Rumm wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird will be
negligible - it will have a tiny capacitance.

But. Won't the bird experience the effect of the arc that
Will strike between it and the conductor as it approaches?
I should think that would be a deterrent.

Just what voltage do you suppose that fence is running at? (its purpose
being to discourage livestock from touching it, not toast it from a yard
away!)

(I now have a mental image if a Frankenstein's laboratory style
electrical setup, with electrical arcs climbing jacob's ladders etc)

Sorry John, I was posting in the middle of the night from my
crippleberry. I thought we were still talking about super-grid lines.
A spark must jump between the approaching object and the wire.

Easily done...

Still it could make for a good "you were only supposed to blow the
bloody doors off" moment, when testing the new electric fence, if a
small quadruped touches it and then bursts into flames ;-)

(not so good for the critter mind you!)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article , dennis@home
scribeth thus


"The Natural Philosopher" wrote in message
...


I see dozens of birds perching on all the wires right next to my
house. Medium and low voltage. Swallows, pigeons, crows etc.

33KV overheads here are used a lot by raptors and pigeons

Fairly sure I've seen birds on the big stuff - 132KV and up. But I cant
swear to it because the nearest is a long way away.

Overhead lines can get hot under load.
You can hear the rain sizzle as it lands.
Birds aren't going to cook themselves.


In the Deniverse yes ...

.... here on planet Earth more like HV corona discharge...

--
Tony Sayer

In article , dennis@home
scribeth thus


"Martin" wrote in message
...

Haven't you ever seen men jumping onto HV cables from helicopters? They
have a lot more capacitance than a small bird. The birds will be fine

Yes.
They have a probe to bond the copter to the wire before the man gets killed
by the current going through him.

Must be that metal wired suit they use then;!?..

The current arcs across several inches as the probe is attached.


--
Tony Sayer

On Sat, 01 Sep 2012 08:19:37 +0100, Martin Brown
wrote:

On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

I always assumed that's why you rarly see birds perching on the actual
phase wires, and when you do, they (the wires) are probebly dead.

x-post uk.d-i-y

Main reason is probably that the big EHT mains cables are too large a
diameter for most bird to perch onto. You often see birds perched on the
HT 40kV lines which are more suited to their feet.

The bird only feels a current from charging and discharging its almost
negligible self capacitance - treating a bird here as a uniform
conduction sphere of radius about 0.05m for convenience. I doubt it even
feels it at all - might enjoy having warm feet in winter though.

Bilge!

Birds hate power lines because you can see their bottoms. Pylons are
high so no tweety birds.

Trees & bushes are lower so there are more tweety birds.

Now get to ground level and we have ducks, geese, chickens and all the
rest of the more sensetive avian society

How many people have flashed their naughty bits on pylons?

HN

On 01/09/2012 18:29, John Rumm wrote:
On 01/09/2012 14:11, Graham. wrote:
On Sat, 01 Sep 2012 13:57:06 +0100, John Rumm
wrote:

On 01/09/2012 06:52, Graham wrote:


John Rumm wrote:
On 31/08/2012 22:35, Graham. wrote:
On Fri, 31 Aug 2012 22:01:10 +0100, Curlytop
wrote:

Deux set the following eddies spiralling through the space-time
continuum:

http://www.specsavers.co.uk/2012-eye-test/birds/

Anyone notice anything wrong in that picture?

Qb lbh zrna gur gbgny nofrapr bs nal cngu jurer ryrpgevp pheerag
pbhyq sybj?

That's not the whole story, remember the gold leaf electroscope at
school?

Current will flow into the bird until it attains the same
potential as
the wire. The charge they take will depend on their size. If the wire
is carriing AC, the current flowing into and out of the bird will
alternate.

True, but the current flow to charge and reverse charge the bird
will be
negligible - it will have a tiny capacitance.

But. Won't the bird experience the effect of the arc that
Will strike between it and the conductor as it approaches?
I should think that would be a deterrent.

Just what voltage do you suppose that fence is running at? (its purpose
being to discourage livestock from touching it, not toast it from a yard
away!)

(I now have a mental image if a Frankenstein's laboratory style
electrical setup, with electrical arcs climbing jacob's ladders etc)

Sorry John, I was posting in the middle of the night from my
crippleberry. I thought we were still talking about super-grid lines.
A spark must jump between the approaching object and the wire.

Easily done...

Still it could make for a good "you were only supposed to blow the
bloody doors off" moment, when testing the new electric fence, if a
small quadruped touches it and then bursts into flames ;-)

(not so good for the critter mind you!)




But handy if you like ready roasted rabbit.

;-)

--
Moving things in still pictures

On Sep 2, 1:14*am, wrote:

How many people have flashed their naughty bits on pylons?

http://www.telegraph.co.uk/earth/ear...?frame=2325416
http://preview.tinyurl.com/9yqgl79

A macaque monkey, with a baby clutching onto its torso, crosses power
lines above a parking lot in New Delhi

In message , tony sayer
writes
In article , dennis@home
scribeth thus


"Martin" wrote in message
.. .

Haven't you ever seen men jumping onto HV cables from helicopters? They
have a lot more capacitance than a small bird. The birds will be fine

Yes.
They have a probe to bond the copter to the wire before the man gets killed
by the current going through him.

Must be that metal wired suit they use then;!?..

Deniverse


--
geoff