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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Interesting Conundrum



 
 
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  #21  
Old November 19th 19, 02:33 PM posted to uk.telecom.broadband
Andy Burns[_5_]
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Posts: 452
Default Interesting Conundrum

Roderick Stewart wrote:

ADSL and VDSL have to be automatically rate-adaptive (because they use
infrastructure not originally designed for the purpose) and apparently
a consequence of this is that routinely powering down your modem would
be interpreted by the system as a frequently occurring fault. It can't
tell the difference between a deliberate break in transmission


most modems/routers have "dying gasp" which would allow telling the
difference, but apparently BT's kit ignores it
  #22  
Old November 19th 19, 02:38 PM posted to uk.telecom.broadband
Andy Burns[_5_]
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Posts: 452
Default Interesting Conundrum

Andy Burns wrote:

most modems/routers have "dying gasp" which would allow telling the
difference, but apparently BT's kit ignores it


Though SIN 498 does mention dying gasp, so maybe they support it now?



  #23  
Old November 19th 19, 11:41 PM posted to uk.telecom.broadband
Martin Brown[_2_]
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Posts: 225
Default Interesting Conundrum

On 19/11/2019 13:04, Roderick Stewart wrote:
On Tue, 19 Nov 2019 09:55:39 +0000, Martin Brown
wrote:

The
single modem/router/wireless box is hardly even warm to the touch and
has about half the power consumption of the two box arrangement it
replaces, which seems an important important property for something
that has to be powered 24/7.


I wish they would power down whan there is no local internet traffic and
wake on lan activity but apart from that they are fine.


ADSL and VDSL have to be automatically rate-adaptive (because they use
infrastructure not originally designed for the purpose) and apparently
a consequence of this is that routinely powering down your modem would
be interpreted by the system as a frequently occurring fault. It can't
tell the difference between a deliberate break in transmission and an
accidental one, so if it happens frequently it will assume a fault and
lower the sync rate in an attempt to achieve greater reliability, so
in time you might not be getting the best speed your line is capable
of carrying. Therefore it's best to leave ADSL and VDSL modems
continuously powered.


Continuously powered but only doing the bare minimum to keep alive the
connection. I am not convinced that you are right about a daily line
drop either at least not once the initial training phase is completed.

We have power cuts often enough to test the hypothesis and as far as I
can see there is no loss of sync speed on a single or even two line
drops in a row on any given day. That's typically what happens.

They seldom lose or restore power cleanly so that it comes up for 5s and
then collapses permanently and vice versa when it is restored.

(This is not the same as with DOCSIS, which *does* use cables which
are chosen for the purpose, and where the sync speed for a particular
account *can* be guaranteed, even if you switch off at night).

Rod.



--
Regards,
Martin Brown
  #24  
Old November 20th 19, 12:17 PM posted to uk.telecom.broadband
NY[_2_]
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Posts: 54
Default Interesting Conundrum

"Martin Brown" wrote in message
...
Therefore it's best to leave ADSL and VDSL modems
continuously powered.


Continuously powered but only doing the bare minimum to keep alive the
connection. I am not convinced that you are right about a daily line drop
either at least not once the initial training phase is completed.

We have power cuts often enough to test the hypothesis and as far as I can
see there is no loss of sync speed on a single or even two line drops in a
row on any given day. That's typically what happens.

They seldom lose or restore power cleanly so that it comes up for 5s and
then collapses permanently and vice versa when it is restored.


We have occasional days when the power goes off for about 1 second and then
comes back on - sometimes for an hour or so, sometimes only for a few
seconds before repeating the outage. The electricity company say it's due to
vegetation touching overhead (11 or 33 kV?) lines, tripping a circuit
breaker which restores itself. I wonder what happened to preventive
maintenance: checking that no trees are growing too close to HV lines, and
pruning them *before* they become a problem.

The worst phase was on Saturday evening where it was up and down like a
lady-of-the-night's nether garments (!), sometimes there was as little as
two seconds between one brief outage and the next. I think I counted about
15 outages in the course of a couple of hours.

Eventually there was a longer power cut - long enough for someone to have
turned the power off deliberately while they cut back a few branches - and
since then, the power has been fine.

By the end, the router had got into silly mode - even after a controlled
power cycle, it gave an error when I tried to ping any external domain name
or IP address (apart from my ISP's own website), though DNS was working to
translate domain name to IP address. That was cured by restoring the router
to factory state, having already determined that another spare router worked
fine.

But even after all this, the VDSL sync speed was still the same: the
repeated power cycling and reconnecting to VDSL hadn't triggered the
exchange to lower the sync speed that it negotiated with the router.

  #25  
Old November 20th 19, 02:53 PM posted to uk.telecom.broadband
Martin Brown[_2_]
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Posts: 225
Default Interesting Conundrum

On 20/11/2019 11:17, NY wrote:
"Martin Brown" wrote in message
...
Therefore it's best to leave ADSL and VDSL modems
continuously powered.


Continuously powered but only doing the bare minimum to keep alive the
connection. I am not convinced that you are right about a daily line
drop either at least not once the initial training phase is completed.

We have power cuts often enough to test the hypothesis and as far as I
can see there is no loss of sync speed on a single or even two line
drops in a row on any given day. That's typically what happens.

They seldom lose or restore power cleanly so that it comes up for 5s
and then collapses permanently and vice versa when it is restored.


We have occasional days when the power goes off for about 1 second and
then comes back on - sometimes for an hour or so, sometimes only for a
few seconds before repeating the outage. The electricity company say
it's due to vegetation touching overhead (11 or 33 kV?) lines, tripping
a circuit breaker which restores itself. I wonder what happened to
preventive maintenance: checking that no trees are growing too close to
HV lines, and pruning them *before* they become a problem.


They do it in summer round here about half a day spent lopping bits off
during a planned power cut usually with a fortnight's notice and
sometimes with road closures while they work on the tricky bits.


Eventually there was a longer power cut - long enough for someone to
have turned the power off deliberately while they cut back a few
branches - and since then, the power has been fine.


More often than not ours is a tree falling across the lines in a storm.
Amazingly the newer steel cored 3 phase aluminium distribution cable can
sometimes support the weight of a tree without snapping. I have a
picture of a tree supported by such a cable during one winter storm.
Three thin copper wires just go ping though.

By the end, the router had got into silly mode - even after a controlled
power cycle, it gave an error when I tried to ping any external domain
name or IP address (apart from my ISP's own website), though DNS was
working to translate domain name to IP address. That was cured by
restoring the router to factory state, having already determined that
another spare router worked fine.


Usually cycling the power on a router in a controlled manner is enough
to get them back into the land of the living. Mine sometimes gets into
an impossible state where it clocks up error seconds in realtime but
does not reboot because it thinks it still has sync

But even after all this, the VDSL sync speed was still the same: the
repeated power cycling and reconnecting to VDSL hadn't triggered the
exchange to lower the sync speed that it negotiated with the router.


I think it is a lot more robust than people give it credit for. If you
get just the right kind of CRC errors as the link fails then maybe you
can lose speed for 24 hours or so but I haven't seen it happen other
than when there was a serious physical fault on the line.

--
Regards,
Martin Brown
  #26  
Old November 20th 19, 04:56 PM posted to uk.telecom.broadband
NY[_2_]
external usenet poster
 
Posts: 54
Default Interesting Conundrum

"Martin Brown" wrote in message
...
We have occasional days when the power goes off for about 1 second and
then comes back on - sometimes for an hour or so, sometimes only for a
few seconds before repeating the outage. The electricity company say it's
due to vegetation touching overhead (11 or 33 kV?) lines, tripping a
circuit breaker which restores itself. I wonder what happened to
preventive maintenance: checking that no trees are growing too close to
HV lines, and pruning them *before* they become a problem.


They do it in summer round here about half a day spent lopping bits off
during a planned power cut usually with a fortnight's notice and sometimes
with road closures while they work on the tricky bits.


In the 6 months since we've lived in this house, we've had power cuts on 8
occasions (and that's since August when I started keeping a note of them -
there were quite a few before that). Always the same form: power goes off
for about a second and then comes back; sometimes one-off, sometimes rinse
and repeat for an hour or so. Everyone in the village is annoyed that the
electricity company can't work out what is causing them - they trot out the
standard excuses about birds flying into wires, vegetation touching wires
etc. But we never hear afterwards what the exact cause was for any given
outage - we don't know whether it is indeed something shorting to earth or
whether it's an over-sensitive trip protector or occasional *genuine* load
(as opposed to shorts to earth) that exceeds spec.

If it's birds flying into wires, then they must be a suicidal lot round
here, and if it's vegetation then someone's not keeping track of trees that
are growing too close to power lines. Why should the problem be so much
worse in this village that anywhere else we've lived (including a far more
remote location in a tiny hamlet of five houses and two farms) - Northern
Powergen can't answer that one.

Apparently one of our neighbours was advised to buy a UPS, which is an
admission that the power is *likely* to go off.


At our previous house I remember there was once a planned power cut for
maintenance, with residents notified in advance by letter. They anticipated
that the power would be off for a couple of hours, but that was just to
cover themselves: in the event, it was off for only a few minutes while
there was a lot of whirring of chainsaws near a pole-mounted transformer
down the road, probably trimming ivy off the pole. Most of the time that
they were on-site was getting a cherry-picker into location and removing it
afterwards.

  #27  
Old November 20th 19, 05:20 PM posted to uk.telecom.broadband
Martin Brown[_2_]
external usenet poster
 
Posts: 225
Default Interesting Conundrum

On 20/11/2019 15:56, NY wrote:
"Martin Brown" wrote in message
...
We have occasional days when the power goes off for about 1 second
and then comes back on - sometimes for an hour or so, sometimes only
for a few seconds before repeating the outage. The electricity
company say it's due to vegetation touching overhead (11 or 33 kV?)
lines, tripping a circuit breaker which restores itself. I wonder
what happened to preventive maintenance: checking that no trees are
growing too close to HV lines, and pruning them *before* they become
a problem.


They do it in summer round here about half a day spent lopping bits
off during a planned power cut usually with a fortnight's notice and
sometimes with road closures while they work on the tricky bits.


In the 6 months since we've lived in this house, we've had power cuts on
8 occasions (and that's since August when I started keeping a note of
them - there were quite a few before that). Always the same form: power
goes off for about a second and then comes back; sometimes one-off,
sometimes rinse and repeat for an hour or so. Everyone in the village is
annoyed that the electricity company can't work out what is causing them
- they trot out the standard excuses about birds flying into wires,
vegetation touching wires etc. But we never hear afterwards what the
exact cause was for any given outage - we don't know whether it is
indeed something shorting to earth or whether it's an over-sensitive
trip protector or occasional *genuine* load (as opposed to shorts to
earth) that exceeds spec.


I presume you are on overhead distribution.

Ours was classic three wire by the roadside. Insulated once long ago but
with long strips of it dangling down. On a wet night you could watch it
arcing and sparking as it bridged the different phases and dimmed the
lights. Most times it didn't trip for that but sometimes it would.

If it's birds flying into wires, then they must be a suicidal lot round
here, and if it's vegetation then someone's not keeping track of trees
that are growing too close to power lines. Why should the problem be so
much worse in this village that anywhere else we've lived (including a
far more remote location in a tiny hamlet of five houses and two farms)
- Northern Powergen can't answer that one.


Vegetation is one cause. But round there they do keep on top of it.
Degradation of the cables themselves was the problem with ours that
ultimately led to them replacing it. Also because the local pumping
station startup dimmed the lights of everyone at 6pm daily.

Apparently one of our neighbours was advised to buy a UPS, which is an
admission that the power is *likely* to go off.


It is good advice if you live in a remote rural area as is having a
generator set. We can be down for a few days if there is a major outage
in bad weather since remote rural is first to fail and last to get fixed.

At our previous house I remember there was once a planned power cut for
maintenance, with residents notified in advance by letter. They
anticipated that the power would be off for a couple of hours, but that
was just to cover themselves: in the event, it was off for only a few
minutes while there was a lot of whirring of chainsaws near a
pole-mounted transformer down the road, probably trimming ivy off the
pole. Most of the time that they were on-site was getting a
cherry-picker into location and removing it afterwards.


There are some quite long runs by the roadside with trees round here.

--
Regards,
Martin Brown
  #28  
Old November 20th 19, 06:22 PM posted to uk.telecom.broadband
NY[_2_]
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Posts: 54
Default Interesting Conundrum

"Martin Brown" wrote in message
...
I presume you are on overhead distribution.


Ours was classic three wire by the roadside. Insulated once long ago but
with long strips of it dangling down. On a wet night you could watch it
arcing and sparking as it bridged the different phases and dimmed the
lights. Most times it didn't trip for that but sometimes it would.


No, we're on underground for the 240 V. It's the high voltage feed to the
nearest substation or pole-mounted transformer which is the problem.
Apparently with the most recent outage the power company could see that
circuit breakers were tripping but they couldn't work out where the fault
was. They said it might even have been a fair distance upstream of the feed
to our particular village, and that when one HV feed tripped, the load was
too great for the remaining redundant feeds which then tripped because of
overload rather than short to earth.

I hadn't realised that any attempt was made to insulate the wires of a
three-separate-wire 240 V feed on poles. Obviously the wires need to be
insulated if they are bundled into a single three-wire cable between poles.

I remember when I was at school some bright spark (pun not intended!)
decided to throw a metal coat hanger repeatedly at the three-wire 240 V
wires leading from the road - and eventually he managed to get the coat
hanger to short between two phases. There was a loud bang and lots of
sparks, and the coat hanger fell to earth with one section still glowing
cherry red. It had a notch out of it and the metal was blackened, where the
spark had melted the wire locally and a longer length had heated up.

So those wires weren't insulated.

  #29  
Old November 20th 19, 07:15 PM posted to uk.telecom.broadband
Woody
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Posts: 773
Default Interesting Conundrum

On Wed 20/11/2019 17:22, NY wrote:
"Martin Brown" wrote in message
...
I presume you are on overhead distribution.


Ours was classic three wire by the roadside. Insulated once long ago
but with long strips of it dangling down. On a wet night you could
watch it arcing and sparking as it bridged the different phases and
dimmed the lights. Most times it didn't trip for that but sometimes it
would.


No, we're on underground for the 240 V. It's the high voltage feed to
the nearest substation or pole-mounted transformer which is the problem.
Apparently with the most recent outage the power company could see that
circuit breakers were tripping but they couldn't work out where the
fault was. They said it might even have been a fair distance upstream of
the feed to our particular village, and that when one HV feed tripped,
the load was too great for the remaining redundant feeds which then
tripped because of overload rather than short to earth.

I hadn't realised that any attempt was made to insulate the wires of a
three-separate-wire 240 V feed on poles. Obviously the wires need to be
insulated if they are bundled into a single three-wire cable between poles.

I remember when I was at school some bright spark (pun not intended!)
decided to throw a metal coat hanger repeatedly at the three-wire 240 V
wires leading from the road - and eventually he managed to get the coat
hanger to short between two phases. There was a loud bang and lots of
sparks, and the coat hanger fell to earth with one section still glowing
cherry red. It had a notch out of it and the metal was blackened, where
the spark had melted the wire locally and a longer length had heated up.

So those wires weren't insulated.


We must be lucky then. Lived here 29 years come the end of this month
and you can count power outages (of which we were aware) on the fingers
of one hand.

--
Woody

harrogate three at ntlworld dot com
 




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