On 10 Sep 2003 15:31:14 -0700, robsignals wrote:

Wanderer wrote in message . ..

snip

On any interconnected system, the National Grid being a prime example,
events are by definition related.

Bad choice of words on your part, I think.How can a lightning strike in
the west country and a 3rd party cable damage that happened to occur at
more or less the same time in the west midland be related? No, that may
never have happened, but I give it as an example of the flaw in your
argument.

This incident was caused by a
classic very simple installation 'cock-up' made 2 years ago and not
discovered or exposed since; system design, configuration and incident
response were correct and supplies would have been securely maintained
otherwise.

Not true. Somewhere between design, configuration and commisioning a
current multiplier was wrongly set, and was not picked up by testing
procedures that should have picked it up.

snipped the actual details, read with interest, but there seem to be
some notable gaps that raise even more questions [1]

Yes. Knowing the very strict and thorough commisioning and testing
procedures that once were enforced, one is left wondering whether
corners have been cut since privatisation.

They were carried out but I guess those engineers assumed they had
been handed over correctly installed equipment and never thought to
check the relay rating, pity they aren't brightly colour coded.
Simulating real life faults is simply not possible or wise.

Paragraph 177 in the report is quite explicit about the procedures used
to commission the protection. I would not fault them as written.
Certainly the responsibility for returning a circuit to commision in
good and proper order rests *exclusively* with the guys carrying out the
work.

Reading the full report my impression is of a well run and financed
operation not obviously damaged by privatisation with London area
investment running at £50m pa. Ironically the duplicate circuit,
Wimbledon - New Cross No.1, is out from 1/7 to 28/9 for upgrade and
refurb.

Lessons have been, painfully, learnt and the relay error is not likely
to happen again. All 45,000 are being checked (none found after
9,000). I would say the system is now secure

I don't share your confidence. The report paints a picture of a calm and
ordered working environment that almost certainly did exist two or three
decades ago. I suspect those working for NGT might have some difficulty
in recognising this environment today.

building extra lines
would be very expensive. The LT loss of supply is rather laid on EDF,
the London distribution operator, who chose to operate their Wimbledon
132kV Substation in a way that resulted in LT and others losing supply
when the Grid was able to maintain the full load without interuption,
and should have reconnected LT in a couple of mins at most. I get the
impression there was only one engineer in their Control who didn't
know what hit him...

Unlikely if they operate a centralised control system. But.....

[1] The gaps:-

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.

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.

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?