"Richard Catlow" wrote in message
m...
Wanderer wrote in message
. ..


It would have been nice to see an actual schematic of the network at
Hurst s/s. They have three supergrid t/frs on site. I'm guessing that
each would almost certainly be independently controlled, and
consequently capable of isolation, by circuit breakers on the hv and lv
sides of the t/fr.

Not necessarily so if this was configured as a mesh connected 4
breaker site or a three and a half breaker bay with the SGTs banked
with incoming feeders and disconnected by inter-tripping and power
operated dead break isolators.


Buchholz alarms are usually t/fr specific in the control room, so why
did the NG control engineer apparently disconect the incoming circuit
and not isolate the tranformer indicating the alarm? If this had
happened the overload situation would not have occured.

I wonder if the bucholz alarm was not for the main SGT, but for a
Voltage Transformer associated with the 275kV incoming circuit feeding
the bar. In which case the control engineer would have no option but
to de-energise the circuit. Operational procedures for certain VT's
call for immediate switchouts of certain 132kV, 275kV and 400kV VT's
to prevent explosions. The SGTs at this site step down to 132kV and if
they failed they would not have caused an impact upon the 275kV
circuit. My money is on the VT as this would cause the loss of a 275kV
circuit and some outgoing 132kV circuits. NR lost both Bromley grid
132kV circuits as a result of this.

It would also be interesting to compare areas of responsibility and
manning levels for this part of their network now and say 25 years ago.
What level of authority and/or delegation of that authority holds today
compared to 25 years ago?

NGC's main control centre is at Wokingham in Berkshire, which I have
visited. They have two backup control centres, locations of which I
cannot reveal in public.

Laanberris and Hinckley.

Mark

In article , Mark Drury
writes

"Richard Catlow" wrote in message
om...
Wanderer wrote in message
...


It would have been nice to see an actual schematic of the network at
Hurst s/s. They have three supergrid t/frs on site. I'm guessing that
each would almost certainly be independently controlled, and
consequently capable of isolation, by circuit breakers on the hv and lv
sides of the t/fr.

Not necessarily so if this was configured as a mesh connected 4
breaker site or a three and a half breaker bay with the SGTs banked
with incoming feeders and disconnected by inter-tripping and power
operated dead break isolators.


Buchholz alarms are usually t/fr specific in the control room, so why
did the NG control engineer apparently disconect the incoming circuit
and not isolate the tranformer indicating the alarm? If this had
happened the overload situation would not have occured.

I wonder if the bucholz alarm was not for the main SGT, but for a
Voltage Transformer associated with the 275kV incoming circuit feeding
the bar. In which case the control engineer would have no option but
to de-energise the circuit. Operational procedures for certain VT's
call for immediate switchouts of certain 132kV, 275kV and 400kV VT's
to prevent explosions. The SGTs at this site step down to 132kV and if
they failed they would not have caused an impact upon the 275kV
circuit. My money is on the VT as this would cause the loss of a 275kV
circuit and some outgoing 132kV circuits. NR lost both Bromley grid
132kV circuits as a result of this.

It would also be interesting to compare areas of responsibility and
manning levels for this part of their network now and say 25 years ago.
What level of authority and/or delegation of that authority holds today
compared to 25 years ago?

NGC's main control centre is at Wokingham in Berkshire, which I have
visited. They have two backup control centres, locations of which I
cannot reveal in public.

Laanberris and Hinckley.

Mark


Used to be a control centre at Becca Hall near Leeds as well but that
has now closed. Suspect it may have been CEGB as opposed to National
Grid.
--
Andrew
Electronic communications can be altered and therefore the integrity of this
communication can not be guaranteed.
Views expressed in this communication are those of the author and not
associations or companies I am involved with.

In uk.railway, Graham Murray writes:

And I suppose that the disability anti-discrimination laws would have
prevented the company employing him on account of his colour
blindness. :-)

Oops, that should read 'prevented the company *not* employing...'

Wanderer said:

Some of this seems fairly elementary - I know this is easy to
say with hindsight - but are the electricity supplies really
this badly managed?

No, they're exceptionally well managed, as it happens. What seems
to have happened here is that somewhere along the line, someone
either mis-set a relay or failed to notice that a relay had been
mis-set. The procedure for checking that relay appears to be
well-written.

Well don't we need managers who can prevent problems like this, not
managers who can't? All we're hearing so far is excuses about how
hard it is to fit relays correctly. Didn't you point out in another
post that low voltage high current tests of these 'protected'
circuits were perfectly feasible? Don't the contractors who put the
system together have to demonstrate to their customers that the
system works as required?

Simple problems like the wrong setting for a protection relay should
be avoidable surely?

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

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

Richard Catlow said:

One other observation. If Mr Game is a quality Guru, perhaps he
should offer his services to NGT?, he obviously knows better than
those within NGT who have a professional knowledge of the system
and its requirements, a skill which Mr Game's posts show complete
lack of knowledge of, even though I and others have tried to
educate him, to the point where he accuses the more knowlegeable
of us of knowing nothing (see his earlier posts), despite the
fact that some of us work in the industry or hand in glove with
it - for example I run the electrification design department of
NR.

If that's me you're talking about, I don't recognize your
description. I haven't put forward any theories, just raised some
straightforward questions on system testing. Thanks for your attempts
to educate me, keep 'em coming! I don't think I accused anyone of
knowing nothing. Others have pointed out that tests of the circuits
were perfectly feasible using low voltage equipment. What you're
doing is raising a technical fog over a simple management failure
(another poster also characterises this as a management rather than a
technical failure).

What happened in those contract tender/bid review meetings when the
question of commissioning of the new system was raised? Did somone
say - don't bother, all those protection devices will stop anything
serious happening, we've done the calculations, no need to test it,
let's save some money?

As for quality gurus, if there's one thing they learn, it's how to
sniff out engineering bull**** at 50 metres. That's not directed at
anyone personally on here, before someone goes off the deep end.

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

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

robsignals said:

I wonder how Mr Game will respond if, or probably when,
he's involved in an embarrasing cock-up...

I expect I would protect my arse, like anyone else. That's why we
have independent reviews/audits/investigations.

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

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

On Sat, 13 Sep 2003 22:46:15 +0100, Chris Game wrote:

Wanderer said:

Some of this seems fairly elementary - I know this is easy to
say with hindsight - but are the electricity supplies really
this badly managed?

No, they're exceptionally well managed, as it happens. What seems
to have happened here is that somewhere along the line, someone
either mis-set a relay or failed to notice that a relay had been
mis-set. The procedure for checking that relay appears to be
well-written.

Well don't we need managers who can prevent problems like this, not
managers who can't?

You can put in place all the management controls you like. It don't stop
humans screwing up from time to time. Try a dose of real-world life.

On 12 Sep 2003 11:50:36 -0700 someone who may be
(Richard Catlow) wrote this:-

It would have been nice to see an actual schematic of the network at
Hurst s/s. They have three supergrid t/frs on site. I'm guessing that
each would almost certainly be independently controlled, and
consequently capable of isolation, by circuit breakers on the hv and lv
sides of the t/fr.

Not necessarily so

I think this is the problem. The report presents a view and I have
no doubt has been Campbelled to give maximum support to that view.

However, it does not tell us why the power supply to (part of) the
underground failed for such a long time. No doubt the report's
authors will claim that this is nothing to do with them, but is the
responsibility of another company. The Michael Howard approach. The
mass media have been deflected, at least for the moment, but I
imagine party politicians and others are still looking for a proper
explanation.


--
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.

David Hansen wrote in message . ..
I think this is the problem. The report presents a view and I have
no doubt has been Campbelled to give maximum support to that view.

On the contrary, the report suffers from being written in unexplained
engineering language and fails to really convey the sheer
improbability of events. I do agree that it raises as many questions
as it answers probably due to the speed it's been produced.

However, it does not tell us why the power supply to (part of) the
underground failed for such a long time. No doubt the report's
authors will claim that this is nothing to do with them, but is the
responsibility of another company. The Michael Howard approach. The
mass media have been deflected, at least for the moment, but I
imagine party politicians and others are still looking for a proper
explanation.

Yes, LU's loss of power was indicated, though not explicitly stated,
to be EDF's fault. They went into some detail about how 'we
understand..' EDF were operating their system and their contigency
plan that should've reconnected LU almost immediately but not why they
didn't (I suspect EDF were simply overwhelmed by the scale of the
event). NG made it clear that through-out they were able to supply
EDF's full Wimbledon load including LU. It comes down to NG's and
EDF's seperate Wimbledon sub-stations being operated independently
when really they should be treated as one unit but I don't think
that's a recent problem.

On 16 Sep 2003 17:14:41 -0700 someone who may be
(robsignals) wrote this:-

It comes down to NG's and
EDF's seperate Wimbledon sub-stations being operated independently
when really they should be treated as one unit but I don't think
that's a recent problem.

I would be interested in a schematic of the arrangement there. I
wonder if one will ever be provided?


--
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.