NOA RGI

[Deleted]

I was at North Acton today in order to take a trip over the crossover to the west of the station used for the east-west reversing move (never been over it before). While on the platform, I noticed that the rail gap indicator fixed to the wrong-road starter at North Acton platform 2 has been bagged up. Would anybody happen to know why that is?

Ta.

[North End]

Jan 11, 2015 18:31:01 GMT tut said:

I was at North Acton today in order to take a trip over the crossover to the west of the station used for the east-west reversing move (never been over it before). While on the platform, I noticed that the rail gap indicator fixed to the wrong-road starter at North Acton platform 2 has been bagged up. Would anybody happen to know why that is?

Ta.

Would normally be done either if the indicator is defective and permanently illuminated, or if section switches have been operated at a location then the indicator may be spuriously illuminated depending on which section of track the indicator is connected to. I'd suggest that in the case you describe it's more likely to be the latter reason.

In either case, arrangements would normally be made that if the section in advance is discharged for any reason power control staff would also discharge the section in the rear as a precaution.

[Deleted]

Thanks for that North End

Could you remind/tell me (I can't remember if I ever knew! ) what section switches do?

[hobbayne]

Section switches when operated can divide up a traction current section into smaller sections.
www.trainweb.org/tubeprune/tractioncurr.htm#Traction%20Current%20Supply

[Tom]

It is almost certainly the second of the reasons North End suggests.

A number if years ago, while we were commissioning signalling modifications at White City, the person testing couldn't work out why the RGIs on the EB starters were not lit as the current was off all around us. After doing some investigation in the wiring diagrams, we worked out that while current was off at White City, the logic to light the RGIs was derived from a current on line relay at North Acton (where the current was still on) and sent down to White City where it was used.

From memory, it works in a similar way on the WB road; the Current on Line Relay is at White City and the 'on/off' logic used for the RGI at North Acton is sent there from White City.

[Deleted]

Thank you for the info

So, am I right to surmise that the RGI at North Acton would have been lit, because traction current was off at White City - which would obviously have been no good at all as traction current was very much on at North Acton?

[Tom]

Exactly that.