On 2018-07-06 15:05:43 +0000, Roland Perry said:

In message , at 14:33:57 on Fri, 6 Jul
2018, Anna Noyd-Dryver remarked:
Roland Perry wrote:
In message , at 13:01:35 on Fri, 6 Jul 2018,
Anna Noyd-Dryver remarked:
Right, here’s some Actual Facts copied from another forum.

quote
As I understand it, it was loss of all signalling power to Streatham
Junction Remote Interlocking area. Ex-Southern Region area signalling
installations usually have three seperate incoming power supply sources,
but in this case there was a catastrophic failure of a part of common
equipment. Other sources state that NR has had to bypass the equipment in
hard wiring to get it working again, but before it could do that it first
had to determine what had caused the original failure, and also monitor the
temporary setup to make sure a hidden fault didn't reoccur and cause even
more damage.

I wonder what it was - they'd have pretty quickly been able to eliminate
back-hoes, smoking substations, and National Grid technicians with
finger trouble.

From the end of my post:

“Signal power feed triple redundant 3 input BUT the changeover swiitch
(single point of failure) was what burnt out”

I meant - what caused it to burn out? Just old age, or was it my
suggestion that when one of the grid feeds failed for a random reason
(they do, which is why one has three) the subsequent load via two of
the contacts on the contact breakers was too high?

We had an incident not long ago during an electrical refurbishment
where, IIRC, the main switch "fell apart". It took several days for a
replacement to be sourced from abroad (Germany, I think) and during
that time a major site ran on generators (parts of it didn't run at all
for some of the time).

Sam

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