Notably on the AM£s - the Glasgow Blue Trains had to be substitiuted by steam for a few weeks until the problem was rectified (oh, dear - pun not intended)
I guess if it was de-laminating there would be a risk of it damaging shoegear.
It would definitely not be more efficient to install third rail because it's not suitable for high-speed operations and less efficient at such long distances given the lower voltages and less distance between substations. Plus the cost of any conversion wouldn't be worth the expenditure even if it were equally as good.
Which is actually why we haven't seen any meaningful conversion of DC to AC...
Not in the UK, but Belgium and the Czech Republic (at least) are progressing DC OLE to AC OLE conversion.
Well if you've already got OLE it's another matter, as the biggest issue with going from no OLE to having OLE is bridge clearances.
It's a lot easier for bridge clearances, but you've still got to manage the DC to AC transition which is, if anything, more difficult if you're trying to use the same OLE structures.
True but that can probably be achieved with little clearance work within more generous continental structures gauges, already with wires.
Although system changes on the move are becoming fairly routine today, with old-fashioned voltage switching border station yards mostly a thing of the past.
Indeed - it's easier to have a multi-voltage train and a short gap (or overlap) between systems, rather than trying to get 2 systems to co-exist over a significant length. Hence why the 3KV DC - 25KV AC conversion is interesting, as it means that the existing DC area must be readied for AC while still handling DC before it's changed over. Especially when you look at e.g. the French 9KV DC trial for upgrading their 1.5KV DC lines, despite there extensive 25KV AC network. Does anybody know how that trial went/is going?
It has been full answered and corrected - but yes, 81-84 definitely had mercury arc rectifiers and I remember them well. I also remember well all the hype about 87101 being Thyristor control. I have a full set of photos back in the UK of all of these.
Current demand upon 3rd rail, for "day to day" train operating speeds in excess of 100mph, would risk the reliability of the current infrastructure - so, yes, we won't see that happen any time soon.
Absolutely.
Fair enough, I guess in principal a trolley thrown off a bridge would cause just as much problem to DC anyway as it would AC
I would have thought it would cause much less mechanical damage (to the 3rd rail anyway, the available current would probably vaporise the trolley!).
A nice solid metal connection between conductor and running rails will trip the current off before any meaningful damage can occur.
Not necessarily, because normal load currents are so high on 3rd rail, and high volt drops are permitted for economic rrasons, fault protection is poor. Many low impedance, but not effectively zero impedance faults, such as a trolley or beer can will not cause protective devices to operate.
Indeed. 4th rail overcomes this issue, as a separate relay can provide protection for even fairly high impedance faults between conductor and running rails.
I'd be surprised if they were caused by something as low impedance as a shopping trolley. Don't know any details though.
A trolley might not be a "nice solid metal connection" if it's just resting on the track. Also compare the cross-section of the trolley metalwork to that of the fat cables used for traction power, which are also made of a better conductor.
