"Road Runner" wrote in message
...
: Depresion wrote:
:
: Why isn't this plastered across all the US news channels the way there
power cut
: was across all of ours?
:
: A 34 minute power failure affecting 10m people is far less serious
: than an 8 hour power failure affecting 50m people.
: --
: remove RRR to reply


AND .... because the world ceases around California, New England, Mexico
and Canada - with a minor blip to the north, and out in the Pacific.
Flatworld is ruled from Washington and Silcon Valley.



DW down under

In article , Martin
writes
In article , David Hansen
writes
Typically the standby generator can only power a small part of the
building load. Non-essential circuits are shed as the generator starts
up. With the generator running it may not be desirable to go back to
the external supply automatically if it does become healthy, it might
fail a minute later. Thus the building may run with only essential
circuits for some time until people are happy with the external supply.


In these days where everything is computer controlled and your
servers are probably the most important business-critical device (see
the cases of various supermarkets which have to close for the day
because their accounting software is on the frizz), keeping them
working also needs air-conditioning. So when things like this happen
you'll be sitting in the dark, bathed only by the strangle glow of
computer screens, unable to do many jobs that require manual dexterity
- like going for a pee in a totally dark toilet - but in a nice,
comfortably cooled environment.

Personally I have no problem going for a pee in a dark toilet - neither
do totally blind people. However it is recommended that men sit down on
this kind of occasion.



--
Five Cats

David Hansen wrote in message . ..
On Fri, 29 Aug 2003 21:22:02 +0100 someone who may be Chris Game
wrote this:-

Two large failures seven seconds apart is stretching coincidence a
bit don't you think?

As I understand it the first fault was in equipment and the second
in a cable. If speculating I would guess that the second fault was
due to an undetected incipient fault on the cable, which was unable
to cope with an increased load.

David, I'm not too sure that is the case. Hurst is equipped with two
400kV to 275kV supergrid transformers and feeds New Cross via two
cable circuits. Under normal operating practice, Wimbledon has three
incoming 275kV circuits (power being absorbed by Wimbledon) and two
outgoing circuits to New Cross (power being supplied from Wimbledon to
New Cross).

From NGC's press statement on Friday the 29th, they admit that the
first fault was on a transformer at Hurst. (Note: "a transformer", not
both units) The second fault was that which occured at Wimbledon which
NGC states as "stopping flows on a 275kV cable between Wimbledon and
New Cross" causing the blackout.

Taken at face value, that appears fine, but probe deeper. Why could
power not be maintained via the other SGT at Hurst and the other cable
circuit from Wimbledon to New Cross?

Here is my theory:

1) There was an outage of at least one circuit between Wimbledon/New
Cross/Hurst for maintenance or renewal at the time of the outage, thus
limiting the freedom to manouever around the first problem at Hurst.
My bet is that this was one of the Hurst to New Cross feeders. At the
same time, the other circuit, being fed from the other SGT, goes down
as a result of the transformer failure.

2) From NGC's website, the Wimbledon to New Cross Feeder 1 and 2 have
a circuit rating of 810 and 660MVA respectively. From a summer loading
perspective, I doubt that the load exceeded 700MVA (peak winter load
is predicted at 1051MVA) On this basis, I would expect even the
smaller cable to be able to withstand this load for more than forty
minutes.

3) There was a protection operation at Wimbledon (whether really
called for, or a maloperation) which either:

a) Caused "Stuck Breaker" protection to operate (for real or
maloperation), which tripped out the 275kV bar (Causing the whole
275kV bar to be lost and hence cuts the supply to New Cross and causes
the loss of the 132kV bar, causing the loss of supply to Lots Road BSP
- thus affecting the Tube)

OR

b) There was some other protection maloperation causing the 275kV bus
to be lost (such as bus zone with the bus being operated solid),
although this is much less likely than (a) above.

The reason why I would pick 3(a), is that NGC spokesmen were reported
as saying that all similar equipment around the country was being
checked. Given that protection at 275kV is always duplicated with
different manufacturer's relays and uses different settings at each
site, I feel that it would be very unlikely that a similar set of
relay combinations and settings can be found at other sites. I am
inclined to believe that an apparently stuck breaker is the cause
here. (Stephen Timms in his interview stated that a circuit breaker
was to blame, although that could mean a physical failure or a breaker
protection scheme.)

Well, I will have the facts at my fingertips upon my return to work
tomorrow.

Richard

Chris Game wrote in message . ..
James Farrar said:

Presumably talking after a briefing by the National Grid people.

Perhaps.

And even if so, there's no guarantee that the Minister's comments
accurately reflect the content of the briefing.

Come on! You think the posters on here know what they're talking
about? In detail?

I certainly know one or two. Let's see, from memory:

1) The head of NR's electrification design branch
2) The guy who plans all NGT/Railway connections and interactions
3) The chap who investigated the entire loss of Malaysia's Ntional
Grid in 1996 as a result of poor planning and equipment failure
4) Certain staff responsible for the operation of the Railways entire
electriciation network

These are just the ones that I am aware of who post or lurk here. No
doubt there are others who are either active or retired from the
Railway and / or Electricity industries, those whom lurk and never
post and those who we think are doing something entirely different and
happen to fall into one of the above categories.

In my experience, such posters will either:

A) Make persuasive, reasoned arguments to support their case and
publish their references or sources and advance a theory

B) Who will comment in detail once the facts are known

Whereas others stomp about making vaguely political points, cannot
back up their evidence from external sources, offer opinions, make
good points, ask incisive questions and generally behave in the manner
that USENET promotes - nothing wrong in that at all. Just saying that
some posts come across more credibly than others.

Richard

(Anyone like to guess which job he performs out of the list in 1-4
above?)

On Sun, 31 Aug 2003 15:51:31 +0100, Chris Game wrote:

Wanderer said:

Come on! You think the posters on here know what they're talking
about? In detail?

Err, there are one or two who do or have worked in the Electricity Supply
Industry -

Working a while ago at the coalface doesn't make them expert, or well
informed, as to what happened the other day. Of course people with a
grounding in electricity supply can scotch some of the wilder
assertions on here, but that's not quite the same thing. Till some
investigation report or other is published, what the Energy Minister
reported is likely to be closer to what happened than any guesses
here.

I'm not often given to using profane language, but you are an addle-brained
prick with as much common sense as a turd.

You very cleverly snipped out the bit that said:-

" they tend to be the ones who are waiting to see what NGT's
investigation brings forth....."

Chris Lambert said:

Or maybe we should be addressing the issue of why thousands of
people were angry or shocked by a 40 minute power cut.

That bit's fairly obvious I'd have thought. No-one was telling them
how long it would last, or how long things would take to get back to
normal afterwards. Partly because no-one knew of course, but that
doesn't take away the shock or anger.

--
=============================================

Chris Game chrisgame@!yahoo!dotcodotuk
=============================================

On Sat, 30 Aug 2003 09:41:09 +0100, "Depresion"
wrote:


Now you bring up coaches I've got to ask did the London bus service shut down
the way the one in NY did?

The bus service continued to run. However the traffic congestion was
grim.

Rob.
--
rob at robertwoolley dot co dot uk

On 31 Aug 2003 05:37:32 -0700 someone who may be
(Richard Catlow) wrote this:-

Strictly speaking Dinorwig was not designed as a backup generator,

It would also be slightly difficult to claim that any such scheme is
a generator, because it consumes more electricity than it generates
(unless there has been a change in the laws of physics since I
studied the things).

That is not to say that such a scheme is not very useful however. As
your figures showed it is a good investment compared to
alternatives.


--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me using the RIP Act 2000.

On Sun, 31 Aug 2003 12:35:44 +0100 someone who may be Martin
wrote this:-

In these days where everything is computer controlled and your servers
are probably the most important business-critical device (see the cases
of various supermarkets which have to close for the day because their
accounting software is on the frizz), keeping them working also needs
air-conditioning.

I have been involved in some rather large computer installations.
The halls concerned were air-conditioned. It is a matter of debate
whether such air-conditioning is necessary or, because the
specifications are very difficult to maintain over time, a get-out
clause for the manufacturers.

In the case of a supermarket there is no need for air-conditioning
of the small server(s) concerned. All that is needed is adequate
ventilation. It is, of course, sensible to place this ventilation on
the essential side of the busbars, to ensure that the room and hence
the servers do not become too warm.



--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me using the RIP Act 2000.

On 31 Aug 2003 06:23:23 -0700 someone who may be
(Richard Catlow) wrote this:-

David, I'm not too sure that is the case.

It was only speculation:-)

One of my lines of thought has been how the Grid circuits are
operated in terms of open rings and automatic switching. Also how
the protection is graded. I have been puzzled as to how the stated
faults could have caused the loss of supplies from all the bulk
supply points. On the face of the given faults there appears to only
be a case for loss of supplies from Hurst. I will read your message
later this evening with interest.


--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me using the RIP Act 2000.