Not really ‘Sustainable Energy’ but possibly interesting to a community interested in all things power…
Network rail had an overvoltage for 20s knocking out a big chunk of signalling gear. They have been remarkably forthcoming on the issue (which I like).
Interesting that despite multiple supplies, they only failover on a power cut not on an overvoltage. Classic blinkered approach to system design / business continuity; focusing on the ‘usual’ problem rather than the thing that actually causes the issue i.e. Power Cut v Unsuitable Power Supply. There is always the possibility the overvoltage was far enough back to affect all 3 of their suplies, but in that case you would expect a more widespread disruption.
The interaction between signalling systems and the traction supply is a very complicated topic, because of necessity the traction supply uses what is essentially a earth return - the running rails.
That may well have contributed to the problem described.
Is that true of 3rd Rail supply (which this is rather than OHP)?
IIRC from that brown out last year, there was something about the supply to the signalling being separate from the track side supply. I suspect it varies by location.
Key thing to me was that the system could not failover to a ‘good’ supply (of the 3 available) or shut off the bad one.
I don’t live down there, but if it’s not 4 rails, and even if it is, then there still has to be some quite significant earth currents flowing, if only from leakage across wet insulators in weather like this.