Interesting power issue

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).

There is a bit more on the twitter thread

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.

I’m not an expert but there is a third rail to the side of the running rails, but no 4th rail AFAIK.

I think it’s London Underground that is a 4-rail system.
Yes, it is London Underground

1 Like

I’m surprised that the power supply is an operating company responsibility rather than Network Rail’s?

But it doesn’t seem any more than a minor glitch when compared to the signalling problems Greater Anglia have.

And that in turn is nothing compared to the overall operational mess that is Northern Rail.

Let’s not get into that sort of discussion - it’s out of place here.

What type of discussion is that, Robert? You mean the subject of the entire thread?

We are talking about power supplies.

It’s not. That is a post by Network Rail.