Power cut stopping Steam drawn train.

[ericmark]

So electric trains don't automatic stop with a power cut.

 

[RandomGrinch]

So electric trains don't automatic stop with a power cut.

Not quite!
For example, if the OLE was to fail, then electric trains would eventually stop!
However, even then, some electric trains are 'electro-diesels' e.g. Bi-modal Class 800, class 802, class 755 FLIRT etc.
When they are about to run off the wires, they can start up their Generator Units to supply traction current.
Although there is a set procedure for starting the GU - it's not best practice to run off the wires with the pantograph still raised!

 

[plugwash]

My understanding is that if traction power is lost on overhead systems, the train will open a circuit breaker and disconnect the pantograph from the transformer until the power is back in specification to reduce arcs when power is re-established. It's quite normal for a train to briefly lose traction power because of running through a neutral section. I'm not sure how far a typical train can coast.

Obviously if signalling fails the trains will have to stop to avoid crashing, afaict that would be down to the drivers though.

There was an issue not long ago though where power was not lost, but the frequency dropped and the computers on the Class 700 trains decided to shut themselves down and required a service engineer to reset. Blocked up all the areas where class 700s operate north of the river (south of the river is third rail and so was not directly affected) for quite some hours.

There is a separate system to auto-drop the pantograph if a train runs off the end of the wires (triggered by over-extension of the pantograph) but it doesn't always trigger quickly enough to stop the pantograph smashing into something.

 

[RandomGrinch]

I'm not sure how far a typical train can coast.

Given the mass of the train can be hundreds to thousands of tons (even a 2 car pacer is about 50t) and the low rolling resistance, trains can coast for miles (depending on many factors!).
A couple of anecdotes here:

How far can a train roll?

Bit of a strange one and probably depends on various factors such as the train, it's formation, the weather conditions, gradient etc, but how far could a train roll under its own momentum before it would eventually come to stop? I was thinking it when approaching Reigate recently, where...

www.railforums.co.uk

 

[big-all]

used to have a van[mail] train left redhill at 5.34 am couldnt get into tonbridge station till around 0600 20 miles away motor up to godstone tunnel exit the tunnel at 65-70mph shut off and coast still doing 15-20mph on approach to tonbride 15 miles later slight downhill grade but only averaging perhaps 1 in 300
other examples are motor to selhurst reach about 45mph and coast all the way to victoria about 8 miles away