St Pancras Thameslink class 378

[stuartbaggs]

Was on a Thameslink class 378 service today travelling north towards Bedford.

As we arrived at St Pancras the driver mentioned on the PA that it's possible that the doors would take longer to release here and that he'd do his best to get them open as soon as possible.

Is there an electrical problem or other that would cause this? Odd

 

[superalbs]

Do you mean Class 387?

 

[EM2]

It's to do with GPS. As I understand it, these units rely on GPS to ascertain that they are in the right position, and unless that signal confirms the location the doors cannot be opened.
And of course at St Pancras, the GPS signal has to get through thirty feet of concrete!

 

[asylumxl]

I'm was under the impression it's to do with electrical interference. As far as I know St Pancras has track mounted beacons to tell the train where it is (in addition to the normal GPS). Unfortunately putting 25KV OHLE in a concrete bunker doesn't allow electromagnetic waves to spread out and dissipate, which results in interference.

 

[AM9]

I'm was under the impression it's to do with electrical interference. As far as I know St Pancras has track mounted beacons to tell the train where it is (in addition to the normal GPS). Unfortunately putting 25KV OHLE in a concrete bunker doesn't allow electromagnetic waves to spread out and dissipate, which results in interference.

In other words the installation has had inadequate EMC qualification testing.
ISTR that the beacons were hastily installed when the penny dropped about concrete bunkers not being the best GPS receiving sites in London. If so, then unreliable operation will plague the service until either more immune kit is used or the level of EM interference is dealt with.

 

[MrPIC]

Its the same at Stansted Airport, because you are underground the train throws a hissy and won't open the doors until the driver manually selects the train's location.

 

[Class377/5]

It's to do with GPS. As I understand it, these units rely on GPS to ascertain that they are in the right position, and unless that signal confirms the location the doors cannot be opened.
And of course at St Pancras, the GPS signal has to get through thirty feet of concrete!

GPS is a line of slight tech, it won't work if there us no direct view of outside, ie windows,so places like Victoria have beacons instead.

I'm was under the impression it's to do with electrical interference. As far as I know St Pancras has track mounted beacons to tell the train where it is (in addition to the normal GPS). Unfortunately putting 25KV OHLE in a concrete bunker doesn't allow electromagnetic waves to spread out and dissipate, which results in interference.

Correct. Basically the ASDO beacons were placed on the track. What happened in real world (didn't happen during testing) is the AC through out interference that cancelled out the beacons signal. Both software and hardware mods have been tried with partial success. Hardware mods included changing the 377s physically to a clearer signal so lots of effort has gone in.

The class 700s work slightly differently due to ATO so shouldn't be affected. Testing is already happening advance successfully so should be an issue by the time the 700s come into service next year.

In other words the installation has had inadequate EMC qualification testing.
ISTR that the beacons were hastily installed when the penny dropped about concrete bunkers not being the best GPS receiving sites in London. If so, then unreliable operation will plague the service until either more immune kit is used or the level of EM interference is dealt with.

Problem is that its not universal. It doesn't always affect hence the issues

 

[Crossover]

They were making the same announcement at St Pancras during the first days of running of the 387's last December - of course they were then saying they were new trains and having teething problems/ Sounds like they've run out of excuses now :P

 

[jon0844]

Why couldn't there be a secondary system that doesn't require beacons to simulate GPS, but rather something like an infrared beam that will tell the train it's in the right place?

Clearly the problem needs to be solved by the time the core is needing a train to be in and out in the blink of an eye come 2018.

 

[swt_passenger]

Why couldn't there be a secondary system that doesn't require beacons to simulate GPS, but rather something like an infrared beam that will tell the train it's in the right place?

Clearly the problem needs to be solved by the time the core is needing a train to be in and out in the blink of an eye come 2018.

It has been pointed out a couple of posts ago that the 700s will use a different system for location, part of the ATO.