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Message Digest
Volume 28 : Issue 74 : "text" Format
Messages in this Issue:
Re: To Bury or Not to Bury
Re: To Bury or Not to Bury
Re: under-sea power transmission cables
Re: under-sea power transmission cables
Re: under-sea power transmission cables
Re: under-sea power transmission cables
Re: ISDN (was Re: 2 phone numers on one landline?)
Re: ISDN (was Re: 2 phone numers on one landline?)
Re: To Bury or Not to Bury
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Date: Sun, 15 Mar 2009 16:34:44 +1100
From: David Clayton <dcstar@myrealbox.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: To Bury or Not to Bury
Message-ID: <pan.2009.03.15.05.34.43.528351@myrealbox.com>
On Sat, 14 Mar 2009 02:10:07 -0400, hancock4 wrote:
> On Mar 13, 6:37 pm, David Clayton <dcs...@myrealbox.com> wrote:
>
>> There must be clear and enforced Standards of Performance - like 99.9%
>> (or whatever) overall availability of the service in normal conditions,
>> as well as enforceable conditions for other various contingencies.
> . . .
>> The trouble is (and probably always has been) getting the people who
>> set the conditions to set the appropriate ones, and then actually
>> enforce them.
>
> I can't for outside the U.S. but one weakness of US regulation has been
> not keeping up standards and requirements up to date to reflect changing
> conditions. The regulators will insist upon maintaining an obsolete
> service that only a few use and is costly to provide "for the public
> interest". (Some states may still require party line service even
> though that is now technically obsolete and today a nusiance to
> provide.)
>
> Another problem is that regulators will be very slow in authorizing a
> new service until they figure out what standards to apply. The Bell
> System had developed cellular service and was ready to try it out but
> the FCC sat on it for two years. I believe US television was ready to
> expand circa 1948 and again the FCC sat on that for several years.
There is always going to be a balance between keeping to old ways of doing
things and then trying to change/remove those older things to make way for
new opportunities.
Perhaps with all of these mandated & regulated technology items there
needs to be a set sunset/review date built into them to ensure that
appropriate reviews must take place (rather than be put off by vested
interests etc)?
You can't leave things that utilise public resources in the hands of "the
market", nor can you let out of date regulations hinder change that is
judged to be of benefit to the vast majority - and that's where politics
complicates matters!
--
Regards, David.
David Clayton
Melbourne, Victoria, Australia.
Knowledge is a measure of how many answers you have, intelligence is a
measure of how many questions you have.
------------------------------
Date: Sun, 15 Mar 2009 13:27:48 -0700
From: AES <siegman@stanford.edu>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: To Bury or Not to Bury
Message-ID: <siegman-C7AD5C.13271815032009@news.stanford.edu>
In article <pan.2009.03.15.05.34.43.528351@myrealbox.com>,
David Clayton <dcstar@myrealbox.com> wrote:
> You can't leave things that utilise public resources in the hands of "the
> market", nor can you let out of date regulations hinder change that is
> judged to be of benefit to the vast majority - and that's where politics
> complicates matters!
This is a _very_ good statement -- both of the contrasting halves of it
-- and not just because it's also terse!
------------------------------
Date: Sun, 15 Mar 2009 00:49:04 -0700 (PDT)
From: David Kaye <sfdavidkaye2@yahoo.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: under-sea power transmission cables
Message-ID: <f7fd9a16-0aa9-4287-9f9f-84ba5060660b@r36g2000prf.googlegroups.com>
On Mar 12, 10:07 am, Will Roberts <oldb...@arctos.com> wrote:
> Following up on the discussion of underground high-voltage power
> transmission lines, it's worth noting a project which was under
> consideration in Hawaii.
I'm wondering how safe it is to transport high voltages through bodies
of water. I realize it happens in the Bay Area (the cable that
replaced the Hunters Point power plant, for instance), but does
anybody know how safe this practice is?
I know that rats are drawn to electric cables, which is apparently why
there are so many electrocuted rats who have eaten through cables.
I'm wondering if there is any other danger from running high voltages
through water.
Anyone?
------------------------------
Date: Sun, 15 Mar 2009 20:05:58 GMT
From: Stephen <stephen_hope@xyzworld.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: under-sea power transmission cables
Message-ID: <h2mqr4dv1ltugbup1f0so61kkjqjt2i8de@4ax.com>
On Sun, 15 Mar 2009 12:12:14 -0400 (EDT), David Kaye
<sfdavidkaye2@yahoo.com> wrote:
>On Mar 12, 10:07 am, Will Roberts <oldb...@arctos.com> wrote:
>> Following up on the discussion of underground high-voltage power
>> transmission lines, it's worth noting a project which was under
>> consideration in Hawaii.
>
>I'm wondering how safe it is to transport high voltages through bodies
>of water. I realize it happens in the Bay Area (the cable that
>replaced the Hunters Point power plant, for instance), but does
>anybody know how safe this practice is?
Not good if the power "leaks" - but [isn't ] that ... about getting the cable
design right?
Less flippantly, good insulation should translate into lower loss and
higher transmission effectiveness.
These are getting more common now that offshore wind farms are being
built in many parts of the world, but power feeds to islands or across
big rivers have been around for a while.
50 MW to Jersey in the english Channel from France
http://www.rte-france.com/htm/an/journalistes/telecharge/dossiers/jersey_france_an.pdf
Many subsea cables are DC - usually since they connect different grids
which are not running in sync.
http://en.wikipedia.org/wiki/Electric_power_transmission
So you probably dont like the idea of using the sea as the return path
for the power?
> I know that rats are drawn to electric cables, which is apparently
> why there are so many electrocuted rats who have eaten through
> cables. I'm wondering if there is any other danger from running
> high voltages through water.
The cable has to be shielded from the water otherwise the power doesnt
appear at the far end......
The main thing likely to be sensed by fish and so on is the electric
and magnetic fields, although the electric field may be suppressed by
some cable constructions.
There have been similar issues with telecomms cables, with recent
design needing to be resistant to bites from big fish like sharks.
The theory is they are attracted to the fields from the original
signals in electrical cables. Nowadays such cables are fibre optic so
that isnt an issue, but there will usually be a power feed for a long
cable for the embedded amplifiers.
Current state of the art is around 350 to 400 Km before you need an
amp.
Regards,
stephen_hope@xyzworld.com - replace xyz with ntl
------------------------------
Date: Mon, 16 Mar 2009 00:53:28 GMT
From: Eric Tappert <e.tappert.spamnot@worldnet.att.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: under-sea power transmission cables
Message-ID: <rv7rr456vm8n0ds78b86ji23omb80mkin3@4ax.com>
On Sun, 15 Mar 2009 19:00:31 -0400 (EDT), Stephen
<stephen_hope@xyzworld.com> wrote:
>On Sun, 15 Mar 2009 12:12:14 -0400 (EDT), David Kaye
><sfdavidkaye2@yahoo.com> wrote:
>
>>On Mar 12, 10:07 am, Will Roberts <oldb...@arctos.com> wrote:
>>> Following up on the discussion of underground high-voltage power
>>> transmission lines, it's worth noting a project which was under
>>> consideration in Hawaii.
>>
>>I'm wondering how safe it is to transport high voltages through bodies
>>of water. I realize it happens in the Bay Area (the cable that
>>replaced the Hunters Point power plant, for instance), but does
>>anybody know how safe this practice is?
>
>Not good if the power "leaks" - but [isn't ] that ... about
>getting the cable design right?
>
>Less flippantly, good insulation should translate into lower loss and
>higher transmission effectiveness.
>
>These are getting more common now that offshore wind farms are being
>built in many parts of the world, but power feeds to islands or across
>big rivers have been around for a while.
>
>50 MW to Jersey in the english Channel from France
>http://www.rte-france.com/htm/an/journalistes/telecharge/dossiers/jersey_france_an.pdf
>
>Many subsea cables are DC - usually since they connect different grids
>which are not running in sync.
>http://en.wikipedia.org/wiki/Electric_power_transmission
>
>So you probably dont like the idea of using the sea as the return path
>for the power?
>
>> I know that rats are drawn to electric cables, which is apparently
>> why there are so many electrocuted rats who have eaten through
>> cables. I'm wondering if there is any other danger from running
>> high voltages through water.
>
>The cable has to be shielded from the water otherwise the power doesnt
>appear at the far end......
>
>The main thing likely to be sensed by fish and so on is the electric
>and magnetic fields, although the electric field may be suppressed by
>some cable constructions.
>
>There have been similar issues with telecomms cables, with recent
>design needing to be resistant to bites from big fish like sharks.
>
>The theory is they are attracted to the fields from the original
>signals in electrical cables. Nowadays such cables are fibre optic so
>that isnt an issue, but there will usually be a power feed for a long
>cable for the embedded amplifiers.
>
>Current state of the art is around 350 to 400 Km before you need an
>amp.
>
>Regards,
>
>stephen_hope@xyzworld.com - replace xyz with ntl
Underwater power cables are always shielded with the shield
effectively grounded to the earth (although it may be used as a
neutral in AC circuits or a return in the more common DC circuits).
This is done for two reasons, one to control the voltage across the
insulation to prevent corona effects and insulation degradation, the
other to provide safety for trawlers who will snag the cable . A side
result saves the lives of sharks and other sea life.
An interesting thing happened with the first fiber optic undersea
cable. Previous electronic cables were coaxial, with the outer
conductor grounded and repeaters were in series feed by DC power on
the inner conductor in a constant current mode. Fiber still needs
power for repeaters (especially for long ocean crossings) and the
first fiber cable used separate conductors for the power feed. On a
test (I believe it was off of the Azores...) the cable failed
catastrophically within a couple of weeks due to shark bites. The
problem was the electric field due to the separate power conductors
attracting the sharks, who thought the cable was dinner. The solution
was to shield the cable and ground the shield, at least on the
continental shelves and in shallow water.
With that adaptation, the major problem with undersea communications
cables these days is fishing trawlers snagging the cable.
E. Tappert
------------------------------
Date: 15 Mar 2009 21:51:06 -0000
From: John Levine <johnl@iecc.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: under-sea power transmission cables
Message-ID: <20090315215106.52830.qmail@simone.iecc.com>
>I'm wondering how safe it is to transport high voltages through bodies
>of water. I realize it happens in the Bay Area (the cable that
>replaced the Hunters Point power plant, for instance), but does
>anybody know how safe this practice is?
Well, if the cable springs a leak, it'll short out, but that's what
circuit breakers are for.
There are some fairly large undersea power cables in use, such as the
330MW one between Connecticut and Long Island. There's a 104km 40MW
AC cable from England to the Isle of Man and a 580km 700MW DC cable
between the Netherlands and Norway. There are also cables in Japan,
which has earthquake issues.
Kona to Honolulu is under 300km so at first glance it should be doable,
or it could be three much shorter hops via Maui and Molokai.
R's,
John
------------------------------
Date: Sun, 15 Mar 2009 13:39:43 -0400
From: T <kd1s.nospam@nospam.cox.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: ISDN (was Re: 2 phone numers on one landline?)
Message-ID: <49BD3D5F.4010406@cox.net>
In article <gpfh07$kcl$1@reader1.panix.com>, wb8foz@panix.com says...
> hancock4@bbs.cpcn.com writes:
>
>
>> On Mar 12, 11:33 pm, Fred Goldstein
>> <fgoldstein.SeeSigSpamb...@wn2.wn.net> wrote:
>>
>>> BUT the [Baby] Bells *hated* Internet with a purple passion (and still
>>> do).
>>>
>> Could you elaborate on these statements? WHY did they hate it back
>> then, and why today? Is there any published literature describing
>> their feelings?
>>
> First of all, because they didn't control it. They were left sitting at
> the side of the road watching their customers err subscribers do as they
> wished; NOT as Ma told them.
Not to mention we've seen people abandoning the Baby Bells in droves
for cellular and VoIP.
I recall reading an article in my local paper that Verizon was down to
holding only 43% of all wireline in the state of RI. It was in the
Providence Journal a few years back but I can't find the original
article.
------------------------------
Date: Sun, 15 Mar 2009 17:46:34 -0700 (PDT)
From: Joseph Singer <joeofseattle@yahoo.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: ISDN (was Re: 2 phone numers on one landline?)
Message-ID: <858779.21321.qm@web52704.mail.re2.yahoo.com>
Sat, 14 Mar 2009 05:57:27 +0000 (UTC) David Lesher <wb8foz@panix.com> wrote:
<<First of all, because they didn't control it. They were left
sitting at the side of the road watching their customers err
subscribers do as they wished; NOT as Ma told them.>>
Which is really no different than the wireless providers *have* done
and who are being dragged kicking and screaming into the modern age.
I seem to remember seeing that Verizon passed on getting the iPhone
(even though a CDMA carrier would not have had the world-wide reach of
a GSM carrier) because they couldn't control everything through their
walled garden approach to telecom. It's really quite a step that AT&T
took when they allowed Apple to control most everything about the
iPhone which is not the normal SOP for AT&T. It's more or less that Apple
opened the floodgates to allow someone other than the carrier to make
all the decisions. In my going to forums probably the number one
thing that bugs people about Verizon's approach is that they put all
their stuff like Brew on their devices regardless of what the customer
wishes.
------------------------------
Date: Mon, 16 Mar 2009 01:59:05 +0000 (UTC)
From: wollman@bimajority.org (Garrett Wollman)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: To Bury or Not to Bury
Message-ID: <gpkbp9$1irk$1@grapevine.csail.mit.edu>
In article <a36b0b0d-af6c-4aff-92b9-cfd9e821450a@a12g2000yqm.googlegroups.com>,
<hancock4@bbs.cpcn.com> wrote:
>I believe US television was ready to expand circa 1948 and again the
>FCC sat on that for several years.
The FCC realized, belatedly, just how much they had screwed it up and
declared a moratorium so they could get it right before they allowed
hundreds of new stations on the air. The Big Northeast Channel
Shuffle was bad enough when they only had to shift a dozen stations
around; it would have been much worse if they hadn't taken a breather
from 1948 to 1952. Remember, the Commission had originally allocated
channels 2, 4, 7, 9, and 11 in both New York City and Albany! (After
the reorganization, Albany lost channels 2, 7, 9, and 11, and channel
4 moved to channel 6; Albany would later get 10 and 13, with the
latter being the only one co-channel with a New York City station.)
-GAWollman
--
Garrett A. Wollman | The real tragedy of human existence is not that we are
wollman@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
Opinions not those | grants to rare events of meanness such power to shape
of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness
------------------------------
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