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.