Could isolators be a solution for when pantographs are not lowered?

[AM9]

Indeed - drivers rarely have to manually do the changeover now, so they are more likely to make a mistake on the rare occasion they do have to

== Doublepost prevention - post automatically merged: 14 Aug 2021 ==


Only when the train stops in passenger service!

Wouild it not be worthwhile having an isolator immediately off the southern end of the City platform followed by a short section of dead contact wire to prevent even a slow train sending a pantograph into the last bit of cover. This would mean that as soon as the first pantograph lost power, an experienced driver would be aware of the drop in power as although 700s can climb the 1:29 with half power, it should certainly be obvious that something had happened. Although the scissors crossover at the bottom of the incline is occasionally used to recover trains, that would be using 3rd rail for those that had ac power issues. If for any reason the dead stub was needed to have power that could be brought back in manually with a single contactor that was integrated with the ground switching in the area.

 

[aleggatta]

I mean, there does seem to be a multitude of mitigation’s available to retrofit, even simply having a warning indicator linked to the current draw in the conductor rail of Farringdon station or directly linked to the signalling, but appreciate that might be deemed ‘too complicated’

 

[AM9]

I mean, there does seem to be a multitude of mitigation’s available to retrofit, even simply having a warning indicator linked to the current draw in the conductor rail of Farringdon station or directly linked to the signalling, but appreciate that might be deemed ‘too complicated’

Actually, wouldn't there be a hazardous condition when the train starts up the slope on ac, the DC earthing is not local and floats above ground away from the earthing point. Putting an ac current onto that may raise the true earth vs track earth potential difference above a personnel-safe level or does the switched-grounding extend well into the DC zone.

 

[GordonT]

The technology for track magnets to automatically open emu circuit breakers at voltage changeover points (on dual-voltage overhead networks) existed in the 1950s. Surely something similar to this which would automatically cause pantographs to be lowered on moving trains could be introduced. Astonishing that there is nothing in place other than Mk1 driver memory to have prevented this occurrence.

 

[Busaholic]

Wouild it not be worthwhile having an isolator immediately off the southern end of the City platform followed by a short section of dead contact wire to prevent even a slow train sending a pantograph into the last bit of cover. This would mean that as soon as the first pantograph lost power, an experienced driver would be aware of the drop in power as although 700s can climb the 1:29 with half power, it should certainly be obvious that something had happened. Although the scissors crossover at the bottom of the incline is occasionally used to recover trains, that would be using 3rd rail for those that had ac power issues. If for any reason the dead stub was needed to have power that could be brought back in manually with a single contactor that was integrated with the ground switching in the area.

You've put in terms I couldn't possibly have voiced what I was thinking too: in my case, I imagined I was missing something important as bring the reason it couldn't be done, because otherwise it seems a no-brainer.

 

[O L Leigh]

I’m unsure of the amount of space available at City, but surely a section of unwired and unobstructed airspace would allow the pan to rise to a degree necessary to trigger an ADD (auto-dropping device) activation. All you need to ensure is that there is enough room so that the pan can rise and then fall before the train travels far enough for it to foul anything.

I’ve no doubt that there are already reminder boards for drivers to drop or raise the pan, so if a driver has forgotten I’m not convinced that a loss of power would immediately be associated with a pan still being raised.

 

[Aictos]

I’ve no doubt that there are already reminder boards for drivers to drop or raise the pan, so if a driver has forgotten I’m not convinced that a loss of power would immediately be associated with a pan still being raised.

There are boards and have been for a number of years that remind the driver to switch between 3rd rail and OHL.

 

[swt_passenger]

I’m unsure of the amount of space available at City, but surely a section of unwired and unobstructed airspace would allow the pan to rise to a degree necessary to trigger an ADD (auto-dropping device) activation. All you need to ensure is that there is enough room so that the pan can rise and then fall before the train travels far enough for it to foul anything.

I’ve no doubt that there are already reminder boards for drivers to drop or raise the pan, so if a driver has forgotten I’m not convinced that a loss of power would immediately be associated with a pan still being raised.

There’s about 100m unobstructed distance (on Google satellite view) and the line speed is relatively low. But that doesn’t seem to be enough - is it possible the ADD isn’t fast enough here?

 

[O L Leigh]

There’s about 100m unobstructed distance (on Google satellite view) and the line speed is relatively low. But that doesn’t seem to be enough - is it possible the ADD isn’t fast enough here?

It might not be the speed of the ADD but rather the speed of the pan rising and falling. If the wire is already quite high then the pan doesn't have so far to travel before the ADD blows the air out, but if the wire is low then it has to rise quite a long way and then come back down again so that it is out of harm's way, all of which takes time during which the train may have travelled quite some distance (obviously depending on how fast it's going). Either way, the problem is that the pan has to come down before it hits an obstruction, and a long section of dead wire doesn't achieve this.

It's interesting that this has been split into a separate thread, because in the discussion from which this was split there is information that the pan should lower automatically subject to certain conditions. Therefore, provided that all the boxes are ticked and the system is working (and being worked) correctly, there should be no need for any other mitigation.

 

[ijmad]

I was wondering if they could use a laser that would cut the power if the pantograph runs through it.

 

[Irascible]

Check if the pan is in physical contact, and then electrical contact, and drop it if there's some suitable lack of either after X seconds ( unless it snags, but you're testing for pressure anyway so you can stop dropping it automatically then too ). After suitable flashing lights/alarms/pointing out of panic buttons anyway.

There is probably a good reason why this isn't already done given how simple the test is, what is it?

 

[Grumbler]

The technology for track magnets to automatically open emu circuit breakers at voltage changeover points (on dual-voltage overhead networks) existed in the 1950s. Surely something similar to this which would automatically cause pantographs to be lowered on moving trains could be introduced. Astonishing that there is nothing in place other than Mk1 driver memory to have prevented this occurrence.

Surely the on-board computers must know where the train is, so could be programmed to lower the pan where there are no wires.