interlockings -- old and new - swanseacsmarkus/processesanddata_old/slides/railway... · solid...
TRANSCRIPT
Overview
• All about Interlockings.
• What, why, when, how, (who? – any guesses).
• Techniques involved.
• Solid State Interlocking.
A Giant Jigsaw
• Ensures Safety:
– Conflicting routes not set.
– Points only move if safe to.
– Signals clear when given conditions are met.
• Must also be fail safe.
Route Setting Process
1. Signaller selects entrance/exit points.
2. Interlocking checks route availability.
3. If available interlocking locks route.
4. Released cancelled when train passes.
5. Consecutive track circuits along route released. (next track released only if previous is.)
6. Signaller informed of track circuit release.
Throughout -- interlocking sets required signals.
Opposing Routes
Routes which require opposite directions of travel are know as opposing.
Here 37-39 and 38-36 are opposing.
Signal Setting
Signals are set relative to a set of given rules.
Signal 17 can clear when:
*can also include time (approach control)
The SSI
• Microprocessor based interlocking developed in late 1970’s.
• First one installed 1985 (Lemmington Spa).
• Invensys (or Westinghouse) involved in production.
• Design consists of several electronic “modules”.
The Multiprocessor Module
• Main module for computation.
• Implements a 2 out 3 voting system.
• Many other modules for trackside communication, memory, signaller interfaces etc
Ladder Logic
• The Westrace interlocking designed by Invensys is programmed using ladder logic.
• Basically a series of Boolean equations.
• Similar to relay logic.
• “Encodes” control table logic.