Not a broadcast antenna fortunately!
I saw some blurb about it yesterday and it did seem rather big.
Antenna suspended from helicopter causes power cut near Balmedie
https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-62940240
I'm surprised that it caused a power cut, as opposed to a brief power blip. If the antenna shorted between two of the three phases on what looked like
11 or 33 kV overhead lines, would that be enough to permanently trip a circuit breaker (or blow a fuse), as opposed to temporarily tripping a breaker that would immediately try re-applying the power to see if the fault has been transient?
On 17/09/2022 21:37, NY wrote:
I'm surprised that it caused a power cut, as opposed to a brief power blip. >> If the antenna shorted between two of the three phases on what looked like >> 11 or 33 kV overhead lines, would that be enough to permanently trip a
circuit breaker (or blow a fuse), as opposed to temporarily tripping a
breaker that would immediately try re-applying the power to see if the fault >> has been transient?
What if it dropped on the power line and remained there?
https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-62940240
I'm surprised that it caused a power cut, as opposed to a brief power blip.
Not a broadcast antenna fortunately!
I saw some blurb about it yesterday and it did seem rather big.
Antenna suspended from helicopter causes power cut near Balmedie
https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-62940240
In article <tg5ftp$8k9j$1@dont-email.me>, MB <MB@nospam.net> scribeth
thus
On 17/09/2022 21:37, NY wrote:
I'm surprised that it caused a power cut, as opposed to a brief power
blip.
If the antenna shorted between two of the three phases on what looked
like
11 or 33 kV overhead lines, would that be enough to permanently trip a
circuit breaker (or blow a fuse), as opposed to temporarily tripping a
breaker that would immediately try re-applying the power to see if the
fault
has been transient?
What if it dropped on the power line and remained there?
Piss spoor bit of flying but if it was looking for minerals in the
ground perhaps it needs to fly low!.
Could have been very nasty for the pilot:(
--
Tony Sayer
Man is least himself when he talks in his own person.
Give him a keyboard, and he will reveal himself.
So how come there was somebody there videoing it at the time?
Not that you would know what was going on from the soundtrack, it just
sounds like a helicopter and wind noise.
Brian
If the antenna shorted between two of the three phases on what looked like
11 or 33 kV overhead lines, would that be enough to permanently trip a circuit breaker (or blow a fuse), as opposed to temporarily tripping a breaker that would immediately try re-applying the power to see if the fault has been transient?
On 18/09/2022 09:33, Andy Burns wrote:
NY wrote:
https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-62940240 >>>I'm surprised that it caused a power cut, as opposed to a brief power
blip.
The frame didn't seem to be anywhere near the pole where the main arc
occurred, then there were two smaller arcs down at ground level so
maybe the cable fell to the ground? The frame doesn't appear to have
any dangly bits
<https://youtu.be/jmvSXZE4MeE>
My impression from watching the video is that the frame looks to get
very close to the top of one of the poles, jerks away, and then there is
a bright light at the top of the pole followed by a smaller one on the ground.
fNY <me@privacy.invalid> wrote:
[...]
If the antenna shorted between two of the three phases on what looked like >> 11 or 33 kV overhead lines, would that be enough to permanently trip a
circuit breaker (or blow a fuse), as opposed to temporarily tripping a
breaker that would immediately try re-applying the power to see if the fault >> has been transient?
I don't think most 11kV lines are equipped with re-closing breakers and
I doubt if 33kV ones are either..
NY wrote:
https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-62940240 >>I'm surprised that it caused a power cut, as opposed to a brief power
blip.
The frame didn't seem to be anywhere near the pole where the main arc occurred, then there were two smaller arcs down at ground level so maybe
the cable fell to the ground? The frame doesn't appear to have any
dangly bits
<https://youtu.be/jmvSXZE4MeE>
So how come there was somebody there videoing it at the time?
On Sun, 18 Sep 2022 16:43:49 +0100, "Brian Gaff"
<brian1gaff@gmail.com> wrote:
So how come there was somebody there videoing it at the time?
Not that you would know what was going on from the soundtrack, it just >>sounds like a helicopter and wind noise.
Brian
It looks like a amateur smartphone video. It was obviously being held
in portrait rather than landscape.
Steve
Its quite hard to hold a phone in portrait mode with one hand though. I wonder why there are not cameras that can work either way without re orientating the phone?
On 18/09/2022 16:43, Brian Gaff wrote:
So how come there was somebody there videoing it at the time?
I would imagine the sight of a helicopter dangling a huge rectangular
frame below it, which looked to be about twice as long as the helicopter,
was sufficiently unusual for someone to video it - and they happened to capture the arcing at the top of the pole and on the ground as the frame *apparently* touched the cables and shorted them and/or caused them to
fall to the ground.
On 18/09/2022 18:35, Liz Tuddenham wrote:
fNY <me@privacy.invalid> wrote:
[...]
If the antenna shorted between two of the three phases on what looked like >> 11 or 33 kV overhead lines, would that be enough to permanently trip a
circuit breaker (or blow a fuse), as opposed to temporarily tripping a
breaker that would immediately try re-applying the power to see if the
fault has been transient?
I don't think most 11kV lines are equipped with re-closing breakers and
I doubt if 33kV ones are either..
OK, so if our village gets short 1-second power blips especially in wet and/or windy weather, what is causing the power to be restored after it
goes off - probably due to overhanging trees touching the wires?
Would it be due to shorts on the 240 V overhead lines between the
substation and the houses, rather than on the 11/33 kV overhead lines
that feed the substation? Do substations have reclosing breakers?
I'm sure when the engineer from Northern Powergen came round, he said
that a) he could see branches touching the high voltage lines, and b)
that the breakers would retry a few times.
I remember one night the power was off and on every few seconds, almost exclusively for short < 5 second breaks, over a period of about an hour.
That sounds like something somewhere is retrying and is not even giving
up after a few failures.
Yes that does sound a little careless. I'd have expected them to keep clear of such wires as being a magnetic field sensing device, it must be somewhat affected by the power lines. Perhaps nobody realised this.
Andy Burns wrote:
<https://youtu.be/jmvSXZE4MeE>
My impression from watching the video is that the frame looks to get very close
to the top of one of the poles, jerks away, and then there is a bright light at
the top of the pole followed by a smaller one on the ground.
Watching it with a full-screen browser
The magnetic field from high-voltage power lines is not very strong and
falls away rapidly with distance.
Liz Tuddenham wrote:
The magnetic field from high-voltage power lines is not very strong and falls away rapidly with distance.
Given the helicopter survey claims to be able to detect minerals 500m underground, is it likely to be pumping-out much power?
The BBC seem to have "dicked about" with the video resolution, unlike the Press
& Journal, who shoved it behind a paywall, this is better when viewed full-screen.
If an overhead wire could be shorted by overhanging trees, it would only
be a 240/440 volt circuit. The 11/33kV lines are regularly inspected
and any nearby trees cut back promptly. In extreme gales, the spans
between pylons on National Grid routes have been known to swing so much
they flash across, but 11/33kV spans don't seem prone to that.
I have definitely seen trees which are taller than 11/33 kV wires (three wires arranged *horizontally* on a head that is supported by a wooden pole
or pair of poles) that run close to the trees. If those trees were not kept pruned, shorting would be possible after a lot of summer growth.
The fact that most of our powercuts are brief suggests that somewhere (whether 11/33 kV or 240 V) there are reclosing breakers.
Are the cables of 132 and 400 kV pylons theoretically able to swing together and touch, or is the amount of slack designed to be small enough that two cables that swing in opposite directions can never touch? I suppose the problem is worst in hot weather when the wires will expand more in the heat.
It sounds as though the electricity distributors in your area are a lot
less paranoid about trees than they are in mine.
NY <me@privacy.invalid> wrote:
[...]
I have definitely seen trees which are taller than 11/33 kV wires (three
wires arranged *horizontally* on a head that is supported by a wooden pole >> or pair of poles) that run close to the trees. If those trees were not kept >> pruned, shorting would be possible after a lot of summer growth.
It sounds as though the electricity distributors in your area are a lot
less paranoid about trees than they are in mine.
The insulators give you a good clue about the line voltage, there are
usually one per phase for 11kV and three per phase (or one much taller
one) for 33kV. Just because a line is insulated to 33kV doesn't
necessarily mean it is running at 33kV; it might just be 'future
proofed' or useable as a reserve in the event of maintenance or
breakdown taking out the normal 33kV feeder.
The fact that most of our powercuts are brief suggests that somewhere
(whether 11/33 kV or 240 V) there are reclosing breakers.
It does, but the lax attitude of your suppliers comes as a surprise to
me.
Are the cables of 132 and 400 kV pylons theoretically able to swing together >> and touch, or is the amount of slack designed to be small enough that two
cables that swing in opposite directions can never touch? I suppose the
problem is worst in hot weather when the wires will expand more in the heat.
My sister used to live within sight of a major 132kV line. She told me
of an evening of spectacular 'fireworks' displays (accompanied by
widespread power cuts) during an exceptionally windy storm. The cables
may not have touched, but they could have come near enough to start an
arc. I don't remember what the temperature was at the time.
NY wrote:
Andy Burns wrote:
<https://youtu.be/jmvSXZE4MeE>
My impression from watching the video is that the frame looks to get very close
to the top of one of the poles, jerks away, and then there is a bright light at
the top of the pole followed by a smaller one on the ground.
Looking again, the frame is bigger (relative to the poles) than I thought and >hence not so far in front of them as I'd thought.
The cross-bar at the top of the pole was hit causing it to bounce back and forth
a couple of times, then the arc happened, presumably the cables broke and fell >causing the second arc on the ground, the third flash happened a long way to the
left near the end of the clip ... maybe it was just a reflection from something
shiny, or maybe it was even someone signalling with a torch?
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