[10-12-2008] Luas Red Line Partially Suspended

[luasuser]

Originally Posted by igy

The trams can't handle a power failure gracefully?
I must say that surprises me; what happens if a big chunk of the ESB grid fails temporarily, all the trams need to be towed back to base?

NO......there are sub-stations along both lines so if a chunk of power fails it would only affect those trams served by that sub-station! there are internal batteries on every tram to allow for the doors to open and close just like emergency lights in buildings. but the battery only last for a short period of time just enough time to park the tram to allow passengers to alight safely. then the tram would have to isolate the battery. Just like a car battery if you left the lights on while you went to get petrol. by the time you got back the petrol would be no good without a battery to power the electrics.
Thats way if a fault happens on a tram, a tram will de-train it's passengers and either return empty back to the depot or be 'stabled' (with its battery isolated) until the fault can be sorted.

[igy]

Yeah, I understand that, and I imagine it's a fairly tricky problem to overcome now that I think about it a little more.
I guess I always assumed if the power failed a battery took over (as you say it does), but when that drained all that was required was to reapply power and some the backup battery would be charged to a point where it could start up the main systems again

(I guess I'm thinking of the example where a phone's battery dies completely and plugging it into a charger won't power it back up immediately, but results in the phone charging the battery exclusively, before later powering back up)