In message , at 13:34:01 on Thu, 5 Jul
2018, Roland Perry remarked:
In message , at 11:50:20 on Thu, 5 Jul 2018,
Anna Noyd-Dryver remarked:
Roland Perry wrote:
In message , at 09:58:26 on Thu, 5 Jul 2018,
Graeme Wall remarked:

Just when you thought it couldn't get any worse…

https://www.bbc.co.uk/news/uk-england-london-44721415

I smell a rat.

It's extremely unlikely that Network Rail has experienced the
simultaneous failure of three separate incoming grid feeds, nor would it
take all day to get just one of them re-instated.

This sounds like the *Network Rail* equipment which merges the three
feeds into the supply to the signalling centre has gone up in smoke.

Any other electricity supply issues reported overnight in Stretham?


Presumably you’re referring to the tweet referenced in that article
“Passengers are advised not to travel from the South into London this
morning due to total loss of signalling power that Network Rail has
experienced on 3 separate supplies in Streatham area.”? I see no
suggestion that it’s external rather than railway-internal power supplies
which have failed.

It's one signalling centre which is without power, thus the "three
supplies" must be those for that centre.

Here's another report from Network Rail (via Simon Calder):

"A generator has been sourced to isolate the power feed and is
expected to arrive at the signalling centre later this morning.
Once the generator arrives, the situation will be re-assessed."

Note, not three generators, one for each of hypothetically three
separate sites.

Note that I've seen the post-mortems of various data centre power
outages. They typically have two grid power feeds, plus generators/UPS
on site. What almost always goes wrong (apart from there being no fuel
in the generator tanks because they've been doing too much test-running)
is that occasionally the fail-over mechanisms, err, fail. [When they
work, few outsiders get to hear about it]

While I'm not speculating about the precise cause of this particular
incident, what's happened before is one of two alternate power feeds
failing for a random reason (the kind of back-hoe or other incident
which is why you have two feeds in the first place), then the "fuses
blowing" on the second feed, because instead of the feeds being sized
for (say) 40% each in normal circumstances, thus 80% when one is
operating alone; they turn out to have been supplying 60% each, and
when one fails the other can't supply 120%.

Anyway, here's a recent example of failing fail-over in a different
transport industry:

https://www.theregister.co.uk/2017/0...data_centre_co
nfiguration/

--
Roland Perry