Design Modification
1. Modifications are only used once installation has commenced. i.e on issue of installation copy.
2. Modification sheets are issued with the following aims:
a. Expediency of issue
b. Clarity of modification
3. Modification process requires strict configuration control of all modifications made to issued sheets.
4. This is achieved by unique identification and full traceability to the affected drawing sheets.
Mod No: ALC-N392-MOD-xxx-Vy-zzzz Zzzz is the Modification number 0001 to 9999, y volume No., xxx SER acronym.
E.g: ALC-N392-MOD-NOG-V2-0001.

Modification Register
• The Group leader shall maintain a register of modification serial numbers, recording details of the modification.
• Modification Register includes
a. Serial number.
b. Number of sheets within the modification.
c. Date of issue of the modification
d. The issuing ECN number.

e. The source of the modification (DGN, TST, INS, TLL, OTH: Design Office, Test Log, Installation Log, TLL comments, Others, Respectively).
f. Originator’s Reference (e.g. the Test Log number)
g. SCR raised as a result of the originator’s comments/logs.
h. A brief description or other commentary as required.

Production and issuing
* Modification production shall follow the Red/ Green method of design as detailed in RT/E/C/11701 as applied to the main design works.

* Where appropriate one drawing method can be adopted and shall show only an extract of the affected portion of the circuit along with appropriate analysis sheet extracts. If impractical two drawing method shall be used.

* Further, where appropriate, full drawing sheets, including analysis sheets, profiles, etc. shall be permitted to be re-bordered as Modification sheets.
* In all cases, the sheets shall be issued with a full reissue of the index sheets and Revision History sheets, up-issued to the next revision.

Indexing and Revision Control
* The modification is produced on Mod sheets as described earlier and then the index is updated to show the sheets affected by the Mod sheet.

* The Revision History reflects the issuance of the MOD sheet and that the Index and Revision History sheets have been updated.
* The cover, index and Revision History sheets will always bear the latest revision letter. For every mod, these sheets revision will be incremented.

* Should modification arise during the commissioning, the same process of MOD sheet issue would be applied, with a subsequent reissue of the book wiring at next higher Version for As Built.

TLL Acceptance of Design Modification sheets
All modification packs shall be provided to TLL for Acceptance, using the same process as the bookwiring acceptance submission.

TBTC Sheets
•Cover sheet
•Index sheets
•Revision History
•Design Sheets             

WRSL/IMR Sheets
•Cover sheet
•Index sheets
•Design Sheets

Cover Sheet
• Take the previous issued design.
• Up revise the revision in RED.

• Overlay new modification number in BLACK.
• Do not change the Version.
• Remove the stage work note (If any).

Design MOD Process (TBTC Sheets)

Index Sheets

• If the design sheet is updated as part of design MOD then take the related design index sheet.
• Up revise the revision in red.
• “ALL NEW WORK” label to be removed.

• In the design modification column place the MOD number in black.
a) ( G+R) for GREEN & RED Sheet
b) 000X(G+Bu) for GREEN & BLUE Sheet
c) 000X(G+R/Bu) for GREEN, RED & BLUE Sheet
d) 000X(Bu/Bn) for BLUE & Brown Sheet
e) 000X(G+R/Bu/Bn) for GREEN, RED, BLUE & Brown Sheet
f) 000X(R) for RED sheet
g) 000X(NEW) for New sheet
– (Note 000X is Design MOD number)

Revision History Sheet
• Use the previous issued sheet from the MOD/Latest version.
• Up revise the revision in red.
• Mention cover sheet, index (affected) & revision history (affected) sheet’s in BLACK.

• Description column to be updated as per Design Log.
• Also update the DES & CHK names in respective column as BLACK.
• NOTE: Do not put Approver’s name in APV column

Design Sheets (Green Sheet)
• Use the latest issued sheet from the MOD(Red sheet)/Latest version.
• Insert the design MOD cell and update the design MOD number. (For the dual sheet show the both design modification number).

• Change the entire circuit into BLACK.
• Show the recoveries in GREEN.
• Do not Up revise the revision.
– NOTE: Blue/Brown colour also change into BLACK

Design Sheets (Example)

Design Sheets (RED Sheet)

• Copy the green sheet and make it as Red sheet.
• Remove the recoveries.

• Add the new items in RED/BLUE/BROWN as required.
• Do not Up revise the revision.

Cover Sheet
• Copy the previous issued design in black.
• Up revise the revision in red.
• Overlay new modification sticker.

Design MOD Process (WRSL/IMR Sheets)

Index Sheet
• If the design sheet is updated as part of design MOD, then take the related design index sheet.
• Up revise the revision in BLACK eg. AA – AB – AC etc.
• Stick new modification box over previous and sign.

• Design Sheets included as part of modification pack are not to be up revised.
• No need to have Green/Red sheets.
• But “# – note” to be provided in BLACK for design sheets.
− eg. #1 – XXX–TL-0001
− #2 – XXX-TL-0002
− XXX-Stn Name

Design Sheet
• Take the RED sheet from previous modification or design and turn to BLACK
• Carry out red & green modification as per scope
• Add heading “DESIGN MODIFICAION SHEET” in Black.

• Add “NOT TO BE FAXED” label in Red.
• Add red & green legend as like TBTC sheets.
• Include a box on sheet showing modification reference number.
• Do not up revise the revision letter.

Design Sheets (Red Sheet)

Important Notes

• If a new sheet is introduced in the design modification then the revision should be “ – “ & put a “NEW SHEET” label.
• In the NEW sheet “DESIGN MODIFICATION SHEET” heading is not required.
• If there is no recoveries in the GREEN sheet then put the label “NO RECOVERIES ON THE SHEET” in GREEN.

• If there is no addition in the RED sheet (only colour change) then put the label “COLOUR CHANGE ONLY” in RED.
• If the sheet is abolished in the design MOD then in the index description has to be changed as “SHEET ABOLISHED AT REV x” and revision remain same.
Note: x – is the revision of the abolished sheet

Important Notes

• While reusing the abolished sheet number, the revision of the sheet must be the same as abolished revision & put a “NEW SHEET” label.

• While transferring the circuits from one sheet to another sheet put a note in Green sheet as “TRANSFERRED TO SHEET ALC-…….” in GREEN & put a note in Red sheet as “TRANSFERRED FROM SHEET ALC-…..” in RED.

• If it is dual sheet then mention both sheet numebrs.

Signalling MOD Design Process, Design Modification,Modification Register,Production and issuing, Indexing and Revision Control, TLL Acceptance of Design Modification sheets, TBTC Sheets,WRSL/IMR Sheets, Cover Sheet, Design MOD Process (TBTC Sheets), Index Sheets, Revision History Sheet, Design Sheets (Green Sheet), Design Sheets (Example), Cover Sheet,Design Sheet,Design Sheets (Red Sheet)

SCS Electronics Rack/Relay Rack Interface

* SELTRAC Overview
* SCS Electronics Rack Overview
* SCS/Relay Rack Interface
* ACE/Relay Rack Interface
* Reference Documents

SELTRAC OVERVIEW

SCS ELECTRONICS RACK OVERVIEW

* Each SCS contains two computers known as ‘INTERSIG A’ and ‘INTERSIG B’.
* INTERSIGS are duplicated for availability – either INTERSIG A or B can be in control, but not both.
* INTERSIG switchover is automatic if one fails.

* Every relay controlled by an INTERSIG output is checked to ensure it is in the commanded position (energised or de-energised) – if not, the INTERSIG shuts down and switches over.
* Each INTERSIG runs the same software, and the I/O allocation for both INTERSIGs must be the same!.

SCS OUTPUTS

* For vital output functions, both CPUs of the controlling INTERSIG are required to energise separate outputs.
* These outputs are combined on the relay rack, and must be in correspondence to give a permissive output to the field (e.g. to lower a trainstop)
* All output circuits energise BR930 series relays.

* There are two types of SCS output cards : Solid State output cards (1-5) and Force Actuated Relay (FAR) Cards (1-4).
* Solid state output cards use transistor switching, and require the load relays to be fitted with diodes for back EMF suppression.

* FAR output cards contain relays for switching the output loads on and off, and do not require diodes on the load relays.
* Point control outputs can only be allocated to certain outputs.
* Output circuit power is 50V DC supplied from the relay rack busbar.

Each output card is controlled by one of the two CPUs.

* For vital functions, one output is required from both CPUs.
* For this reason output cards are paired together to give two outputs.
* For all outputs (except point move outputs):

* Solid state output cards 1 & 2 and 4 & 5 are paired together i.e. the functions on cards 1 & 2 are the same and the functions on cards 4 & 5 are the same.
* FAR cards 1 & 3 and 2 & 4 are also paired together.

* For point move outputs, a combination of outputs from solid state cards 2 & 3 or 3 & 5 is required (refer to relay rack presentation for more details about points).

•Each output relay is individually checked-back to it’s controlling INTERSIG via back contacts (NOTE: point control relays are checked back differently).
•These check-back inputs prove that the relays have operated correctly.

•The check-back input is on when the output is off and off when the output is on!
•If the check-back input does not correspond with the output state, the INTERSIG halts and switches over to the other one.

•The other INTERSIG uses a completely different set of output relays, so it can continue to operate.
•An alarm is raised if the INTERSIG switches over because of failure.

Status Input Example – PESP Inputs – NB only one plunger shown for clarity

•Two types of input: checkback and status
•Each output relay is individually checked-back to it’s controlling INTERSIG via back contacts (points are checked back differently)
•All status input circuits use separate contacts for each input –controlling 2 inputs off one contact is not permitted.

•Each input is read by both CPUs, but vital inputs must be input to two separate input cards, using contacts of two separate relays.
•There are four input cards in each INTERSIG: 1 paired with 3 and 2 paired with 4.

•Point detection inputs can only be allocated to certain inputs
•SCS input circuits are powered from a 24V DC supply within the SCS, which is looped around the relay contacts on the relay rack

•The two CPUs of each controlling INTERSIG provide IMC (Interval Measuring Circuit) outputs to the relay rack, which are energised when the INTERSIG is functioning normally and it is the controlling INTERSIG.
•If a CPU detects a fault, its IMC outputs are de-energised.

•Each IMC output energises a pair of relays on the relay rack – one contactor relay (with high current front contacts) and one standard relay.
•There are checkback inputs for the IMC relays. These inputs are on the IMC card in the INTERSIG – NOT to an input card.

Example – IMC output and checkback circuits for INTERSIG A.

Each INTERSIG has a secure busbar controlled by the IMC contactor relay (example for INTERSIG A shown below).

* When the INTERSIG’s two CPUs are both healthy and in control, the secure busbar is energised.
* The secure bus (ISA B50/N50) is used to power all of INTERSIG A’s output relays.

* INTERSIG B has a separate secure bus (ISB B50/N50) controlled by its IMC contactor relays.
* If the INTERSIG is faulty or not in control, the secure bus is de-energised and all the output relays will be too!

* INTERSIG A and B use separate modems to communicate with the VCC
* The relay rack is responsible for enabling the transmission path of the correct modems and for selecting the correct modems.

MODEM CONTROL

* These circuits enable the correct modem transmission path. (TXEA)R and (TXEB)R are energised directly from the INTERSIG A and B secure bus respectively.

This circuit uses the standard (non-contactor) IMC relays to select either the INTERSIG A or B pair of modems to be the ones that transmit to the VCC.

•Every night, when no trains are running, the SCS does a self-test.
•As part of this test, it switches off it’s IMC outputs.
•This causes the IMC relays to drop, which causes the secure bus to be switched off.

•The SCS monitors its checkback inputs to ensure that all its IMC relays respond to the test (i.e. the back contacts make). If they do, the SCS re-energises the IMC outputs again and returns to normal operation.
•If the test is failed (because the IMC relays have failed), then an alarm is raised.

•On JNUP, there are many inputs associated with Emergency Stop Devices (ESDs). These inputs (and relays) are energised 99.9% of the time (e.g. PESPs, Track Circuit Interrupters etc.)
•These input relays could fail so that they are stuck in the ‘up’ position on these circuits, and nobody would know until the ESD was operated.

•On JNUP we power all ESD relays with their own secure busbar.
•NOTE: This is a separate secure busbar from the one that powers the INTERSIG output relays.

ESD SECURE BUS

•During the nightly IMC test, the IMC relays are switched off. This causes the (DT)R relay to be switched off too.
•The (DT)R relay causes the ESD busbar (called ‘BX110(S/W)(EXT)’) to be de-energised.

•All ESD relay circuits (PESP, TCI etc.) are powered from the BX110(S/W)(EXT) busbar, and so these circuits are also switched off during the IMC test.

•The SCS checks that the ESD relay inputs are de-energised. If they are, all the ESD relays have operated correctly and the test is passed.
•If an input does not respond correctly to the test, an alarm is raised.

ACE Interface

• Each SCS cabinet contains an Axle Counter Evaluator (ACE) which calculates if there is a train in each axle counter block connected to it.
• The occupied/clear status of each axle counter block is passed to the VCC through the modem link.

• Most axle counter blocks do not need a relay on the relay rack.
• However, for some functions, normally for deadlocking points, the ACE provides a relay output to the relay rack.

• The ACE has its own health relays (similar to the INTERSIG’s IMC relays), its own secure bus for its relay outputs and its own special checkback circuit.
• The ACE has two CPUs, similar to the INTERSIG. But, unlike the INTERSIG, the ACE is not duplicated (there is only one ACE per SCS).

•When the ACE is healthy, it energises two contactor relays on the relay
rack, called TKUE1 and TKUE2.
•If the ACE is faulty, one or both of these is de-energised.

The TKUE relays are used to control an ACE secure bus.

All ACE output relays are powered from the ACE B50/N50 busbar, so that if the ACE is faulty, all the ACE output relays are de-energised
and all the axle counter sections appear occupied to the relay rack.

ACE Outputs – Example for axle counter block ‘AC(1)’

For each axle counter block, the ACE energises two relays, .10 QR and .20 QR, both of which must be in correspondence to prove that the block is clear.

•ACE relay checkback circuits for blocks AC(1) and AC(2). Note this is a combined checkback circuit for EVERY RELAY controlled
by this ACE.
•Relays are not checked back individually to the ACE.•This ‘supervision input’ is checked every night by the ACE self-test.

All ACE output relays are powered from the ACE B50/N50 busbar, so that if the ACE is faulty, all the ACE output relays are de-energised
and all the axle counter sections appear occupied to the relay rack.

* During the ACE self test, firstly TKUE1 relay is de-energised.
* This switches off the ACE B50/N50 busbar, all the ACE output relays and the ACE checkback input.The ACE checks that the checkback input is off and then re-energises the TKUE1 relay. The ACE checks that the checkback input is on again.
* The test is repeated by de-energising the TKUE2 relay.

Summary

* Each SCS has two INTERSIGs, either of which can be in control but not both
* Two relays are proved in correspondence for each vital SCS input or output.

* All output relays are checked back to the INTERSIG to proved they have operated correctly
* The IMC outputs are used to provide a secure bus, which switches off the INTERSIG’s outputs if it detects a fault
* The IMC outputs are used to enable modem transmission to the VCC

* Emergency stop device relays are powered from a secure bus
* ACE outputs are powered from a secure bus and are checked back to the ACE

Useful Documents

* Relay Rack Hardware Requirements Specification – 3CU 00550 0210 DTZZA
* SCS Electronics Rack Wiring Schematic – 3CU 10025 BDAA ECZZA

* INTERSIG Parallel Input/Output Interfaces – 3CU 00550 0198 PBZZA
* Station Controller Subsystem Requirements Specification –3CU 00550 0051 DTZZA

•Route secure indicators are mounted at the side of the track and use LEDs to display a route indication to the train operator.
•They are not used in normal operations.
•They are used after a failure:

 to permit failed trains that cannot communicate with the VCC to move over points.
 to permit communicating trains to move over points if a flank point detection has failed.
 to permit trains to move over points if the VCC or loop has failed.

•In addition to seeing the route indicated on the RSI indicator, the train operator must have authority from the control operator over the radio or telephone before moving the train.

A Route Secure (RS) indicator is commanded to be lit or not lit by the SCS, after the required route has been set up.

* Slow-to-drop output relays keep the RS illuminated if the SCS changes over from INTERSIG A to INTERSIG B.

* Because the SCS only commands ‘lit’ or ‘not lit’, the relay rack is required to select the RS aspect based on the detected position of the points in the route.

* Once the SCS commands the RS to light, if the initial conditions (i.e. point detection) are lost the SCS does not switch off the RS. The relay rack has to do it.

RS Lighting Circuit Schematic

The SCS (either INTERSIG A or B) commands the RS to be lit, and the relay rack selects the aspect (based on 10 points normal or reverse, in this example).

Where an RS route goes across an SCS boundary, an interface circuit is necessary, even if both SCSs are in the same SER.

The two SCSs output ‘slot’ indications to each other, indicating that the track is safe for the RS move to enter the territory controlled by it.

* The ISI PR relays are only used as inputs to the SCS
* The ISI PR relays are not used in the RS indicator lighting circuits

Prototype RS Indicator

POINT CONTROL

* SELTRAC controlled points require a total of 3 SCS outputs to control them: Point Command Normal (PCN), Point Command Reverse (PCR) and Point Command Move (PCM).
* To move the points normal requires PCM and PCN outputs on.

* To move the points reverse requires PCM and PCR outputs on.
* PCM outputs can only be allocated to output card 3 (outputs 1-6 only).

* PCR outputs can only be allocated to output card 2 (outputs 1-6 only).
* PCN outputs can only be allocated to output card 5 (outputs 1-6 only).

Point Selection Schematic

•Points to note:
* Outputs from both CPU 1 and 2 required to move the points.
* If the SCS point move outputs have been switched on for 7 seconds and the point detection is not obtained, the SCS switches off its outputs and raises an alarm.

* Points cannot be moved if tracklocking axle counter block is occupied.
* Deadlocking bypass (DLXR) relays can bypass QR contacts if axle counter fails.
* No diversity in NLR/RLR or NWR/RWR functions (i.e. single relays used).

* NLR/RLR contacts are used to operate ground lock.
* Slow to pick NWR/RWR are used to operate the point valve (this gives the ground lock time to disengage before the points try to move).

FOUR FOOT POINT MACHINE

4 Foot Points Movement Clip

Point control schematic

POINT CHECKBACKS

* Point checkback circuits are different from those for RS or other outputs.
* The point movement (WMR) and point direction (WRR/WNR) output relays are checked back separately.
* The four point checkback inputs check ALL point relays controlled by the SCS in each input (summary checkback).

* The four checkback inputs are anti-valent (two normally energised, two normally energised).
* When a point move command is given, the on/off state of all four inputs should be reversed.

POINT DETECTION

* The external point detection circuits are powered at 110V AC with QXR1 transformer rectifiers.
* Two relays are used for normal and two for reverse detection.
* The machine detection contacts must be double cut.

* The detection inputs to the SCS prove correspondence between the detection and the control relay (NLR/RLR).
* Each end is detected separately and input separately to the SCS.
* Detection inputs can only be allocated to input cards 1 and 3.

• Example: Single ended 4-foot point – normal detection schematic

Rail Gap Indicators (RGIs)

•Rail Gap Indicators (RGIs) light up if the traction power on the track ahead is switched off.

•RGIs have three lamps (six on JLE).
•RGIs are not part of the vital signalling system.

* The traction power is monitored by ‘Current On Line’ relays
* We use repeat relays (COLPRs) on the relay rack to control the RGIs
* We also tell the SMC the state of each traction section through SMC PLC inputs generated from COLPRs
* When the traction power is off, the COLPR is energised

* As well as the COL relay, the rail gap indicator is controlled by the points detection
* Only facing points detection is used
* Only routes which are possible in the signalling system are considered

•What would be the controls for this RGI?

•Diverse COLPR relays (and concentric cable) are used even though the circuits are non-vital
•The contacts are used in parallel to maximise the possibility of lighting the RGI and notifying the SMC if one relay fails to pick when the traction power goes off.

Staff Protection Keyswitch

•SPKs are used by maintenance staff.
•When the SPK is operated, it protects a section of the track so that no trains can enter it and no points can be moved.
•The SPK is monitored by the relay rack which passes the status to the SCS.

•If the SCS/VCC detects an SPK is operated, a light is switched on at the SPK to show the maintenance staff that the area of track is .protected.
•When the keyswitch is operated, the key is removed from the switch.
•When the key is put back into the switch, the protection can be released by turning the keyswitch back to the normal position.

* Sometimes the area protected by the SPK is controlled by more than one SCS.
* Note that only one SCS controls the light (the ‘Master’ SCS).

* Sometimes there are two SPKs that protect the same area.

Useful Documents

Relay Rack Hardware Requirements Specification – 3CU 00550 0210 DTZZA
INTERSIG Parallel Input/Output Interfaces – 3CU 00550 0198 PBZZA
Station & Trackside Interface Specification – 3CU 00550 0156 PBZZA

JNUP Relay Rack Design

* Relay Rack Overview
* Design Principles
* Design Features
* Circuit Principles

* RS Overview
* Points Overview
* RGI
* SPK
* Reference Documents

RELAY RACK OVERVIEW

Typical SER Relay Rack Connections

* In the SELTRAC system, the relay rack is the interface between the trackside equipment and the SCS.
* It passes commands from the SCS to the field equipment (e.g. move points)

* It passes information from the field to the SCS (e.g. point detection)

* It also performs a small amount of logic independently of the SCS (e.g. RS aspect selection)
* The relay rack also provides inputs to the SMC PLC

GENERAL DESCRIPTION

* Normally there are two relay racks per SCS.
* Plug connections are used on the relay rack for connections between the SCS and relay rack 1.

* Plug connections are not used anymore on connections between relay rack 1 and relay rack 2 – wires terminate directly on relay contacts or busbars.
* A CCTF (Control Cable Termination Frame – separate from the relay rack) is used to terminate the external cables.

* The relays used are British Rail relays, generally to BR specification 930 or 960 series.
* The wire used is 1mm 2 copper wire with two layers of insulation. The insulation is designed so that it will not give off smoke or poisonous gas if there is a fire.

* Power supply transformers are on a power rack separate from the relay racks
* Rack 1 contains the power busbars, which use miniature circuit breakers (MCBs) instead of fuses for circuit protection, as well as relays
* Rack 2 contains relays only

* At stations where there is no SCS, we use a half-width relay rack.
* This relay rack controls and monitors the local:

 Current On Line relays.
 Rail Gap Indicators.
 Platform Emergency Stop Plungers (PESPs).
 Station Control Room Panels.
 Traction Indicators.

* A repeat relay circuit sends the status of the PESPs to the equipment room with the controlling SCS

POWER SUPPLIES

* The relay rack normally receives 2 separate supplies from the power rack:

 110V AC is used for circuits which leave the equipment room.
 50V DC is used for circuits which stay in the equipment room.

* These supplies are connected to busbars on the relay rack, using miniature circuit breakers on the positive leg and terminals for the negative leg.
* Also the SCS supplies 24V DC to the relay rack for the INTERSIG input circuits, although this supply is not connected to a busbar.

RELAY TYPES

•British Rail specification relays are used.
•The relays operate at 50V DC.
•Single and twin relays are used.

•Contactor relays with heavy duty (high current) front contacts are used for controlling secure busbars
•Relays controlled by INTERSIG outputs (except point outputs) are normally slow release relays (550ms delay). This is to make sure that the trackside equipment controlled by the relays is not affected by INTERSIG switchover (see below).

AC LINE CIRCUITS

Because the London Underground system uses DC electric power for the trains, to avoid problems with interference from this power, it was decided that all signalling circuits that go outside the equipment room would use AC power (at 110V).

* To match the 110V AC power with the 50V signalling relays, a QXR1 transformer rectifier is mounted on the relay rack for each external circuit.
* Each QXR1 can power two QN1 relays.

CCTF

CCTF

* The CCTF is the ‘Control Cable Termination Frame’.
* It is an enclosure fitted with four columns of miniature circuit breakers.
* CCTFs are used to terminate all of the relay rack and SMC PLC cables that leave the equipment room.
* All circuits that leave the equipment room must pass through a 6A circuit breaker in the CCTF (positive and negative legs).

* This circuit breaker is to protect the equipment room from any fault current that might get into signalling cables from the traction power rails.
* The CCTF also contains an earth bar for terminating the cable screens and shields.
* Note that there is also a DCTF (Data Cable Termination Frame) in the SER for terminating data cables (for loop transmissions etc.).

DESIGN PRINCIPLES

For vital circuits, the JNUP contract requires that:
* A single failure should not cause an unsafe situation.
* Failures should be detectable. If not detected immediately, the failure should not cause an unsafe situation if a second failure occurs.

* All circuit design shall provide protection against any combination of open circuits, short circuits, partial open circuits, partial short circuits, oscillations or any other known failure modes of specific components.
* All circuits which enter or leave an SER shall be configured to prevent multiple earths or cable faults from by-passing a part of the circuit.

Relay Diversity(1)

* A BR relay is not reliable enough to meet London Underground’s very high safety targets.
* If a single relay failure could result in an unsafe situation (i.e. most circuits), two separate relays must be proved in correspondence to operate each vital function.

* If one of the two relays fails in the ‘up’ position (due to mechanical failure or contact weld), the vital function (e.g. trainstop) will not operate unless the other relay is also up.
* We do not consider that both relays can fail ‘up’ at the same time (too unlikely).

* We can assume that if one relay fails, the other will continue to operate correctly.
* How can we detect if one of the relays has stuck ‘up’?

* We use relay diversity on the SCS output relays.
* We also have diversity of outputs in the SCS, as one output failure could be dangerous (we use 2 outputs per function).

* We use relay diversity on the SCS input relays.
* We also have diversity of solid state inputs in the SCS, as one input failure could be dangerous (we use 2 inputs per function).

Earth Screened Concentric Cable

* Vital circuits that leave the equipment room are normally carried on earth screened concentric cable.
* A single pair is shown below.

* The central (BX) conductor is surrounded by the return (NX) conductor.
* The fault screen, connected to earth, surrounds each BX/NX pair.
* A 3 pair cable is shown below.

* The design of the cable makes it possible to detect cable faults.
* Because the BX conductor surrounds the NX conductor, any short circuit between these will trip the circuit breaker.
* It is NOT permitted to use a central conductor without connecting the return conductor.

* Any short circuit fault between the NX conductor and the fault screen will raise an alarm on the earth leakage detector.
* Earth screened concentric cables are difficult to bend and are not suitable for installation in all situations.
* Vital circuits in platform areas (e.g. PESPs) do not use earth screened concentric cable because the cable routes are not suitable.

Earth Fault Detection

* Earth faults are caused when cable damage causes the circuit conductors to be electrically connected to the ground.
* They are dangerous because if there is more than one fault, then vital controls can be bypassed.

* There are two different methods we employ to detect earth faults on circuits.

* 99% of circuits will be ‘floating’ with earth leakage detectors monitoring the power supply.
* ‘Floating’ means there is no connection between BX or NX and earth.
* If the circuit leaves the equipment room, the relay contacts will be double cut.

* The earth leakage detector will raise an alarm when the first earth fault is detected on BX or NX leg.
* Note that a single earth fault is not dangerous

* Because there will be many circuits powered from the busbar, the maintenance technician has to test each one until the fault is found.

* An alternative to ‘floating’ supply with earth leakage detectors is the ‘earthed NX’ supply
* This will be used for chairlock point machine detection circuits only (because the chairlock does not have enough detection contacts to double cut them)
* In this approach, the NX is connected to earth and all relay contacts are put in the BX leg only.

* Because there is a connection between NX and earth, any earth fault on the NX conductor will not be detected, but will not be dangerous.
* Any earth fault on the BX conductor will trip the circuit breaker.

* Track circuit interrupters are Emergency stop devices. These are provided at designated locations to provide a vital indication that a train has run into a portion of track in which movements are not permitted (e.g. into trap points or Catch points or past FRLs at terminal platforms).

* It comprises a main body, narrow neck & head which is designed to break off when a rail vehicle passes over it.

* It is bolted to running rail at a position not used by trains for legitimate movement, e.g. beyond the FRL or on stock rail of trap point & shall be insulated from rail.

* The TCI relay circuit will operate at 110v 50Hz.The supply will be electrically isolated from the TCI by a 1:1 isolation transformer, due to the susceptibility of TCIs to Earth faults and extraneous traction currents. The vital relays will be powered via a QXR1 transformer rectifier.

* These circuit will not be routed through the COC, but will be pre-tested and final connections made for phase commissioning.

* The TBTC system will interface with the existing Track Circuit Interrupters to provide automatic detection of an overrun at the ends of lines and sidings including buffer stops and trap points.

* In the event that the Track Circuit Interrupter is activated, the TBTC system will close the tracks associated with the device and will ensure that no controlled train movement is allowed into or out of the affected area.

* The Relay Rack shall continuously report the status of each track circuit interrupter to the SCS Electronics Rack.

* Operation of a track circuit interrupter that is not overridden by the VCC operator shall result in the tracks associated with the device being closed.

* Indication of the track circuit interrupter activation shall be provided at the SMC workstation.

* Track circuit interrupter activation will not have any affect on RM mode train operation and on route secure aspects.

* Nomenclature

Left-hand turnout
 

Right-hand turnout

* Common components
Stretcher Bars
   

* Legal requirement on turnouts
* Insulator required for correct track circuit operation

 Point locking
* LUL provides facing point locks on all points where there are signalledmoves in a facing direction on or potential foul of passenger lines. This requirement includes shunting trains as well as passenger trains. Facing point locks may also be provided in depots or yards but are only mandatory when associated with a signalled passenger train moves.

Switch blade closed. If switch was open, the dab would be in the other port

* In four foot / six foot Point locking is generally achieved using lock dogs on lock notches on the lock bars (Clamplocks use a different system, covered later)

* Lock dogs are moved out of the notches before the drive moves the switch rails and hence lock bars

 Glass Enclosed valve for Point ground Lock

GLASS ENCLOSED(GE) VALVE TERMINALS

GLASS ENCLOSED(GE) FOR POINT GROUNDLOCK(2)

* This valve is a self contained unit with an integral transformer and rectifier, a soft iron core and, in some cases, a capacitor.

* The operation of the valve is controlled from a 100V or 110V AC supply. This is rectified to DC inside the valve enclosure to energise the coil so that the pin valve forced opened. Air is then supplied to the ground lock (WL) unit to lift the locking dab and free the points.

* Loss of air supply or power to the valve will cause the points to remain locked (fail safe arrangement).

Point Auxiliary valve for Pneumatic Point Machines

POINT AUXILIARY NW/RW VALVE FOR PNEUMATIC POINT MACHINES

* The point auxiliary unit has two glass enclosed valve sattached to it: one used to control the supply of compressed air to drive the points normal and a second to drive the points reverse.

* The electrical feed to the corresponding point control is normally maintained at all times, even when all movement is completed. The exception to this is with clamp lock points where the valves are normally de-energised.

TYPES OF POINT MACHINES

* 4 Foot Point
* 6 Foot Point
* Chairlock Point

* Clamplock Point
* M63 or Style 63 Point (Same machine, different name)
* Surelock Point

FOUR FOOT POINTS

* The Four Foot point mechanisms are mechanical devices mounted within the four foot, normally mounted on the
continuous rail side.

* The versions of the 4ft point mechanism are categorized as left-hand and right-hand, depending on whether they are installed to the left or right side of the track center line, with points viewed in the facing direction.

* The following two assemblies differ between the left-hand and right-hand version of the 4ft point mechanism:
1. Point and lock mechanism
2. PL&D Box

FOUR FOOT ESCAPMENT

Escapement is part of mechanism of four foot points driven by motor and having locking dabs for facing point locks and locking ports for ground lock. The points are operated via a crank driven from the escapement.

FOUR FOOT POINTS

* Electro-pneumatic or Electro-hydraulic operation.

a. Electro-hydraulic operation on Central Line.
b. Electro-pneumatic operation on Jubilee, Northern and Piccadilly lines.

* Mounted between the running rails.
* Can be used on Bullhead and Flat Bottom rail.
* Right-handed or left-handed machines in operation.

FOUR FOOT PL&D BOX

FOUR FOOT POINT MECHANISM

FOUR FOOT PL&D CONTACT ARRANGEMENT

FOUR FOOT GROUND LOCK

* In addition to the facing point locks a ground lock must also be fitted to air operated points used for facing passenger train moves. The reason for this is certain types of machine maintain stored energy, which is capable of moving the points under fault conditions, and also without the ground lock the mechanism has very little resistance to movement under vibration.

* A ground lock (WL) is a device which locks the points in position by inserting a dab into one of a pair of ports in the drive mechanism when the lifting magnet is de-energised and the points are fully in the correct position.

* The ground lock must be independently energised. A contact is made when the dab is fully in a locking port. It must also be detected; this can be done separately if not integral to the points detection as is the case with chair locks.

* It is not mandatory to provide either a facing point lock or ground lock when the points are only ever used for trailing moves, unless sectional route releasing is required in which case the points would be held by a ground lock.

FOUR FOOT GROUND LOCK

Railway Signals Use in Thales : The signalling must provide the train operator with clear and unambiguous information about the state of the line ahead under normal operating conditions with sufficient time to react to changes of aspect.For automatically signalled areas, the red and green aspects of the stop signal will inform the train operator whether it is safe to proceed to the next stop signal or not.

Wayside signals. In LUL
User requirements
System requirements
Signalling Functional requirements:
Signals to control train movements as follows:

a) Main running lines: 2 aspect colour light system
b) For shunting movements: to, from and across main lines, mechanical or optical disc signals.

Classification of signals:
Fixed signals:
i) running signals
ii) junction indicator

Shunt signals:
i) calling on signals
ii) warning signals

Repeating signals:
i) running repeating signal
ii) fog repeating signals
iii) platform repeating signals
iv) warning lights in tunnel sidings.

Approach control signals
Draw-up signals
‘X’ signals
‘A’ signs at controlled signals
Remote securing signs.

Automatic signals shall be used on plain sections of track to keep the following trains spaced at a safe distance. These signals shall be operated purely by passage of trains. Automatic signals which protect operational flood gates shall have signal numbers prefixed by code consisting of letter F, followed by letter for the line concerned, and the letter X. Eg. FEX. Stop signals on running lines (Excluding pre-set
Shunt signal) and shunt signals shall be provided with train stop device which operates in conjunction with signal. A signal number prefixed by “X” or “FX” cannot be passed without authorisation from as operating official.

Running signals:
2 aspect colour light signals All running signals use Incandescent (luminous) lamps shall have either a double filament bulb or 2 bulbs per
aspect to enable train service to continue if one filament or bulb fails. The Second filament or bulb shall be underrun and shall act as a standby, should the other one fail. It shall be visibly obvious when one filament of the displayed aspect has failed. LED signal lamp replacements shall incorporate redundant features to achieve the above. Fibre optic or LED running signals may be considered but they shall have facilities to assist close range visibility and redundant arrangement for each aspect.

Three types of signal heads.

i) long range colour light (LRCL),
ii) Short range colour light (SRCL),
iii) Tube tunnel type.
SRCL signals shall be used for running signals on sub surface sections.

Shunt signals:
shunt signals shall be either of Mechanical disc type, with a horizontal red band on a white background, which shall be externally illuminated and cleared by the disc rotating 45 deg. In an anticlockwise manner or the fiber optic type or LED type which are self-illuminating and simulate the action of the mechanical signal by the use of an alternative horizontal or angled red bar of light on a background of white light.Shunt signal which authorize movements to two or more routes shall be provided with a route indicator.

This shall be fixed adjacent to the signal and indicates the route selected in the form of numeral which is illuminated on the display. The first route from the left is numbered “1”, the second from the left “2” and so on.Shunt signals may be situated on the same post as a running signal. In the case of fiber optic shunt signal on the same post as a running signal, the shunt signal aspect shall only be illuminated when it is required to display proceed and the stop running signal showing a danger aspect.

Electro pneumatic shunt signal have no GR. The electro-pneumatic valve that controls the supply of air to the signal is used as the GR coil and the proving contacts that confirm the signal’s position are used in place of GR contacts in the other ciruits.

Junction Indicator:

signals authorizing movements over diverging junctions shall comprise a two aspect stop signal together with one or more junction indicators.Long range junction indicators shall comprise a line of three white lights dependent on whether 1,2 or 3 diverging routes are to be indicated. For

1 route: 45 deg. from the vertical
2 routes: 45 deg. and 90 deg. from vertical
3 routes: 45 deg., 90 deg. and 135 deg. from the vertical.

For standard three lamp junction indicators, at least two lamps shall be proved alight to enable the associated green aspect to clear to proceed.

Junction indicators of reduced size shall be provided at repeating signals of diverging running signals where repeating signal can be sighted at green for the diverging route.

Reduced size junction indicators shall be provided at diverging signals in tunnels.

The Junction Indicator signals shall only illuminate if the selection for the signal is set and the train has been proved to have passed the associated sighting point.

Repeating signals (or Repeaters):

Running repeating signals shall be installed where there is a possibility of train operator not sighting a red signal in sufficient time to bring the train to rest using normal service braking at that signal. They shall display a green aspect when the repeated signal is displaying green aspect and it’s trainstop is lowered, and any track circuits between the repeater and repeated signal are unoccupied. At all other times they shall display a yellow aspect. Trainstops are not required for repeating signals.requirement of platform repeating signals shall be determined by

Some running repeating signals for the signal ahead may be situated below the preceding signal. Both aspects in the repeating signal shall be extinguished when the red aspect is illuminated in the running signal above. This shall be considered when a separate repeating signal of another signal is in close proximity to the signal. The requirement of platform repeating signals shall be determined by operational standards unit in consultation with respective service delivery unit.

Repeater signal located along with other proceeding signals

Where platform repeating signals are specified:

• The signals shall repeat the aspects displayed by station starting signals, shunt signals and junction indicators

• The “proceed at caution” aspect of shunt signal shall be repeated by a black band at 45deg. to horizontal on an illuminated white background.

• Junction indicator shall be repeated by a line of light at the appropriated angle. Fog repeaters shall be provided at a nominal 120m in the rear of the signal they repeat and be mounted at train operators eye level. They shall display a yellow aspect when the signal repeated is at danger or the tracks in between are occupied, and a green aspect when the signal repeated is clear to proceed. The yellow aspect lens shall have a black letter “F” etched into the lens. Fog repeating signals mounted on the same post as running signal are controlled similar way as repeating signals. They can be lit, usually in conditions of reduced visibility, by the operation of ‘fog switch’ at the local station. This illuminates all the fog repeaters in the local area.

• Additional signals shall be provided in tube tunnels to reduce the risk of collision during the application of the “trip and proceed rules”, where the view forward is restricted.

Speed control signals:

speed control signals shall be provided up to signals where there is insufficient overlap to permit a full speed approach. When the train occupies the timing section of the speed control signal, the red aspect shall remain on until

• A full speed overlap is available;

• The speed of the approaching train had reduced to a level appropriate to the overlap available;

• Appropriate “route-away” conditions are satisfied at the signal ahead. Signals which allow a train to draw up to the next signal shall have an extra zero(0) appended to the signal number e.g. EC21 becomes EC210. Incase of single digit numbered signals, two zeros(00) shall be appended, e.g. EC2 becomes EC200.

Fixed red lights

Fixed red lights shall be installed at all locations where there are no further colour light movements in that direction.Single aspect fixed red lights shall be located at the ends of sidings and terminal roads. Three fixed red lights shall be provided for each track, two side-by-side, approximately 3m beyond the normal stopping point and the other at the extreme end of the track, at sidings and terminal platforms. FRLs shall also be located at strategic locations on the running lines in order to prevent wrong road movements.

Red Flashing Light:

The RFL, activated when the out of gauge detector is operated, will act as a warning to the operator not to enter the tunnel. In the event of a flood gate being operated or loss of open detection, then the approaching signals are held at danger and additionally  flashing red lights are located each side of the flood gates are illuminated. 

Fixed red lights 

Current rail gap indicators:

Current rail gap indicators shall be used at current rail section gaps to indicate to train operators if the traction current in the next section is off. The indicators shall consist of three lamps with red lenses in a triangular arrangement in a white enameled front plate with legend RAIL GAP IND in black letters. The current rail gap repeater shall use the same signal with a yellow front plate with a legend RAIL GAP REP Rail gap indicators shall be positioned at the commencement of current rail section gap in the direction of travel. Where a route contains elements of another traction section, a current rail gap indicator shall be mounted on or adjacent to the signal and be appropriately selected for that route.

If a running signal is located less than 100m prior to a substation gap, the current rail gap indicator for that gap may be mounted on the same post, to minimize the confusion for the train operators in terms which comes first due to optical effects. A repeater need not be provided if the indicator is positioned with a station starting signal.

Where a substation gap is located between stations, a co-acting current rail gap indicator shall be provided with the starting signal at the previous station, to prevent trains setting off towards the isolated section.

Current rail gap indicators

Tripcock tester indicator:

Tripcock testers shall be sited at locations which allow for functional in service testing at least once per time tabled round trip. The exact location shall be determined by factors such as normal train movements and avoidance of installation in areas of curved track. The indicator shall be a single circular aspect which shall be illuminated as the train approaches the tripcock tester. It shall be extinguished if the tripcock is satisfactorily tested. The indicator shall be located under or near the station’s starting signal.

‘A’ sign:

A controlled signal which under certain circumstances may be treated as an automatic signal shall be provided with an illuminated ‘A’ sign. The ‘A’ sign shall be beneath the signal concerned and shall display the letter ‘A’ when illuminated and be extinguished when the signal is operating as a controlled signal. ‘A’ signs would typically be provided at sites which are normally left in through running mode, and where interlocking of the through routes is secured, for example by the use of king lever.

Tunnel siding warning lights:

In addition to other protective measures, yellow warning lights shall be installed at 15m nominal intervals in tunnel sidings where there is insufficient protection to prevent trains colliding with a fixed obstruction.

Signals not in use:

All signals not in use shall be covered to prevent the train operator from seeing them. The signal shall have it’s lamps removed and have an opaque black cover. For out door signals a white diagonal cross must be placed on the front of the signal head to indicate that the signal in not in use.

Three aspect ILM controlled signals:

Certain signals on the JL will be controlled directly from the existing IMR with an interface to the TBTC system. These signals will be capable of displaying RED, GREEN and ATC aspects and junction indicators.

The existing levers in the ILM will be retained for these signals.

Two Aspect TBTC Controlled Signals:
At certain locations, two aspect signals, capable of displaying red and ATC aspects, will be controlled directly from the TBTC system.

Jubilee & Northern Line Upgradation Project (JNUP )

SelTrac – Standard Electronic Lorenz Traffic Routing and Advanced Control

Conventional Systems of Train control

Conventional Systems and signalling are based on the fixed block principle.

Fixed Block Principles

1.The Track is divided in to section or block of fixed length
2. Under the fixed block principle to enforce minimum safe separation between the two trains, the following train must never come close to the predetermined fixed distance from the leading train. The fixed minimum number of track blocks of must always separated.

3. The fixed blocks are based on the maximum speed, maximum weight, minimum braking capability.

* To meet the current requirement the system operates under fixed block principle will require much shorter and numerous block which will result in costly wayside changes.

* SelTrac system is based on highly advanced method of achieving safe train separation under the more flexible block principle.

* The minimum safe separation between train is enforced not by fixed block of tracks by elastic block that lengthen and shorten relative to the dynamic train involves.

* As the two train head along the guide way the SelTrac system components are continuously recalculating and enforcing minimum safe distance between them which creates the moving block that separate them.

SelTrac Moving Block Configuration

Moving Block Principles

Vehicle Control Centre (VCC)

• Provides Automatic Train Protection (ATP).
• Commands vehicle operation and route setting.
• Vital Equipment / Software.Each VCC consists of 3 CPUs working in a 2 out of 3 configuration.(JL has 5 VCCs and NL has 7VCCs)

System Management Centre (SMC)

• HMI (Human Machine Interface) for command and supervision
• Automatic Train Regulation.

• Requests operational functions from VCC
• Data Logging
• Non-Vital Equipment / Software

Vehicle On-Board Controller (VOBC)

• Provides Automatic Train Protection. (ATP) and Automatic Train Operations (ATO)
• Control functions commanded by VCC

• Responsible for train movement only within speed/distance permission from VCC
• Vital Equipment / Software

The TOD is a new display unit fitted in the cab that the Train Operator uses.

Station Controller Subsystem (SCS)

The SCS communicates with the VCC
The SCS is responsible for the safety of the system within its area of control
The SCS can perform limited interlocking functions to keep trains moving if the VCC has failedInputs to the SCS include:

• Emergency Stop Devices;
• Point Status;
• Axle Counters; and
• Peripheral Equipments.

The PDIU communicates with the VCC and the train’s VOBC via a docking loop.

The PDIU opens and closes the Platform Edge Doors as directed by the VOBC.

Wayside Equipment – Loops

Wayside Equipment – FIDS and EFIDS

Feed in Device (FID)

Conditions VCC to VOBC data telegrams and supervises inductive loop cable integrityLocated in signalling Equipment Rooms.

Entry Feed in Device (EFID

A standalone FID (has no external inputs or outputs) which is used to initiate communication between the VCC and the VOBC when a train enters the TBTC area.

Sections of the guideway are split into ‘blocks’. A train enters and leaves a block by passing over axle counter heads. The ‘Axle Counter Block (ACB)’ occupancy state is displayed on the SMC.

The ACBs are used for tracking trains which are not communicating with the VCC through the loops.

Track Terminology

Loops

A loop is an inductive cable, laid between the tracks, that the system uses to:
• transfer messages between the VCC and VOBC, and
• determine the position of trains on the guideway.
The maximum length of a loop is 3.2 km.

Each loop is split into ‘positions’ which the VOBC counts as it travels along the guideway. Each ‘position’ is 6.25 metres long. Each position is further split into ‘fine positions’. There are 128 ‘fine positions’ in a ‘position’.

Track Terminology

Each loop also has a ‘crossover’ every 25 meters. The VOBC detects the change in the signal from the loop at each of these ‘crossovers’ to help it determine its position within the loop. Each 25 metre section is sub divided into positions.

There are 4 positions per crossover, hence 1 position is equal to 6.25 metres. Crossovers and positions are not shown on the SMC.

TBTC Modes

Both Passenger and Engineer trains will run on the Jubilee Line. Passenger trains are fitted with two VOBCs (1 active and 1 standby). An equipped train can operate in any one of four TBTC modes. They are:

• Automatic Mode (Auto)
• Protected Manual (PM)
• Restricted Manual (RM)
• Off Mode

Engineer Trains cannot be operated in Automatic Mode.A Train operating in Tripcock protection mode is not controlled by the TBTC system.

Automatic Mode

In Automatic Mode the train doors (and platform doors) are normally opened by the VOBC when the train arrives at a station. A switch in the cab (Automatic Door Open Override) can be selected to allow the Train Operator, and not the VOBC, to open the doors.

When the train is ready for departure, as indicated on the Train Operator Display (TOD), the train operator closes the doors and presses the ‘ATO – START’ button. The train departs the station and travels to its next stop, under the control of the VOBC.

Protected Manual Mode

In Protected Manual the train is under the control of the Train Operator, but is supervised by the ATP system. The TOD displays the maximum speed allowed and the authorised distance to travel. If the train operator exceeds the maximum speed, the TBTC system brakes the train. Door opening and closing is controlled by the Train Operator, although supervised by the VOBC.

Restricted Manual Mode

In Restricted Manual Mode the Train Operator is responsible for the control of speed, motoring, coasting and braking. A speed limit of 17 km/h is enforced by the vehicle, REGARDLESS OF LOCATION AND TRAVEL DIRECTION.

WARNING

OPERATIONS IN RESTRICTED MANUAL MODE MUST ONLY BE CARRIED OUT UNDER THE DIRECT SUPERVISION OF THE CONTROL CENTRE

Off Mode

In Off mode no train movement is allowed, the emergency brake is applied and the propulsion is disabled. The train’s position and status are still reported to the VCC.The Off mode is designed to be used in the following situations:

• When the Train Operator moves from one cab to another; and
• During overnight storage of trains

Tripcock Protection Mode

Certain areas of the guideway are still equipped with existing signalling equipment during the initial stages of the project (called migration stages) and Tripcock Protection is maintained on Transmission Based Train Control (TBTC) equipped trains during migration.
When the train is in Tripcock Protection Mode IT IS NOT UNDER THE CONTROL OF THE TBTC SYSTEM.

WARNING

OPERATIONS IN TCP MODE MUST ONLY BE CARRIED OUT UNDER THE DIRECT SUPERVISION OF THE CONTROL CENTRE

Advantages:
•Shorter Head way
•Complete speed control
•Temporary Speed restriction

•Bi-Directional operation
• Automatic schedule Regulation
• Continuous Train Identification

OVERVIEW
* Basic Requirements of a Point
* Interlocking Principles
* Definitions

* Circuit Definitions
* General
* Components
* Point Machines
* Supplementary Drives

BASIC REQUIREMENTS OF A POINT

* The Basic requirement of a point machine is to move and secure switchrails allowing trains to take different routes through junctions.

* The control and detection circuitry is required to ensure that the points aremoved only at the correct time, and to prove that the movement andlocking have been completed.

* When considering point control and detection, there are numerous requirements that must be satisfied .

* These are detailed below.

1. All points must be equipped with electrical detection circuits which detect that each switch rails locked or secured in the correct positions. This detection include facing point locks and ground locks where fitted.

2. The lie of the points and the position of the controlling device (i.e. the lever/system command) must be proven to be in correspondence when all movements(operation of points) are completed, i.e. in detection circuits.

3. The detection circuits must be independent of the control circuit or drive mechanism.
4. The points must be fully set to the route required (normal or reverse) and any further point movement prevented, before a train approaches the points (route holding arrangements).

5. All points which accommodate the passage of a train in facing direction must have a facing point lock which locks the switch rails in the correct position once movement of the point is complete. Air operated points which have facing passenger train movements over them must also have a groundlock. A groundlock must be detected engaged in the point detection circuits.
6. The time taken for the ‘throw’ of points from normal to reverse or vice versa should be kept as short as possible particularly in complex junction areas. Standards times between 1 and 2 seconds for electro-pneumatic points and between 3 and 5 seconds for ‘all electric points’.

INTERLOCKING PRINCIPLES

The following basic principles apply to the interlocking required for the control and detection of points:
1. All points available for use by passenger trains must be controlled directly from an appropriate interlocking systems (except spring points).
2. Points must only be free to move if they are free from all interlocking and no routes requiring the points have been set.

3. Locking must be maintained until the train crossing the points has cleared the relevant section of track.
4. All points in a signal route and overlap and those giving flank or trapping detection must be locked and proven to be in the required position in the signal control circuitry until the route and associate protection is not required them. The exception to this is under emergency operations where “remote secure” is used, only the points in the line of route need to be locked in the required position.

5. The interlocking once operated must maintain its locking until its release is requested and can be legitimately carried out. The condition for the release may be when the train has cleared the relevant section of the route or the route is free of approach locking.

DEFINITIONS

* Checklock :- A lock on interlocking (point) lever to prevent it going to fully reverse or fully normal until appropriate conditions are satisfied (E.g.lever prevented from going fully reverse until point detection shows switch rails fully reversed) (not applicable where ‘BD’ lock not provided) .
* Controlling Device :- The mechanism used by the Signalman controlling the interlocking to initiate movement of the points. This may be a lever, a switch, a button or a VDU based command.

* Correspondence :- Correspondence occurs when the detected position of the relevant point ends matches the setting of controlling device. If these do not match then points are referred as ‘out of Correspondence’.
* Detection :- The proof of the position of points (and certain locks) that is required by the interlocking.

* Detector rod :- Part of point mechanism attached to switch rail to operate detector mechanism.
* Drive Rod :- The rod connecting a point motor to the switch rails to move the points.

* Escapement :- Part of mechanism of four foot/six foot points driven by point motor and having locking dabs for facing point locks and locking ports for ground locks. The points are operated via a crank driven from the escapement.
* Facing :- A train approaching a diverging junction will be approaching a set of facing points. The train will reach the toe of the switch rail before the crossing or heel of the switch rail first and the direction of the train over these points will be in the facing direction.

* Facing Point lock :-A mechanical device to secure the switch rails in their assigned position once point movement has finished. The manner in which the locking is achieved is dependent on the type of point mechanism.
* Ground lock  :-A supplementary mechanical lock to secure the switch rails in their assigned position once point movement has finished. Used to supplement the facing point lock on air operated points when disengagement of that lock due to residual air pressure or vibration could otherwise result in the unlocking of the switch.
* Interlocking:-  The mechanical equipment or electrical or electronic circuitry which controls the setting and releasing of the points in a predetermined pattern, ensuring that unsafe conditions can not arise.

* Normal and Reverse :- The two possible correct position for the lie of the point ends. The primary (or straight) position is usually referred as ‘Normal’ position, whilst the secondary (or turnout) route is usually referred as ‘Reverse’ position.
* Point Machine :- Where applicable, the equipment which facilitates the powered movement (and securing) of a set of points.
* Switch Rail:- The moving section of rail on each side of a set of points.

* Stock Rail :- The fixed rail on each side of a set of points (against which the switch rail must fit).
* Trailing :- A train joining another line via a converging junction will cross a set of trailing points. The train will cross these points in trailing direction and reach the heel of the switch rail first.

CIRCUIT DEFINITIONS

* Point Circuits : – There are four elements of point circuitry used for electro- pneumatic point layouts:
– Control circuit
– Detection circuit
– Lever Lock Circuit
– Ground lock (WL) Circuit

* Control Circuits :- Points may be called to operate either by the setting of a route or individual point command from a controlling device. This circuit is means of moving the points from one position to the other i.e. normal to reverse or reverse to normal. This circuit operates the point valves ‘NW’ and ‘RW’ for air operated points.

* Detection Circuits :- This circuit provides electrical detection of the position of the facing point lock and the switch rails. Also proved in the circuit is the engaged position of ground lock, if provided.

* Lever Lock Circuit :- This is an electrical lock on the point lever which will prevent the lever or shaft from being moved whilst a train is occupying the track circuits in which the points are positioned. The lever lock circuit is selected over the front contacts of the track relay concerned.

Ground Lock (WL) Circuit

• This circuit ensures that the points cannot be moved without first proving that they are free to move. e.g. when the track locking track circuits are occupied the WL can not be energized as the feed to WL valve is fed over the front contacts of the track locking circuit.

• The WL circuit is an integral part of the points movement as it must be the first item to energies before the points try to move. This is achieved through the contacts in the point lever band ‘NC’ or ‘RC’ in case of lever operation and NLR or RLR in case of TBTC system, to move the points ‘normal’ or ‘reverse’ respectively.

• There is a ‘fail safe’ element to the WL; where by once it has been energised/lifted, the detection circuit of the points will be immediately disturbed.
• Four foot point circuits achieve this by placing a ‘back’ contact of the ‘WL’ in the ‘WKR’ circuit.

• Chair lock points achieve this mechanically; when the WL is energised it engages with the cam follower arm and places the circuit controller contacts in the mid position.

• In Clamp lock circuits the WL has to prove that it has disengaged before the point valves are allowed to operate. This is achieved through additional limit switches placed in the ground lock unit. For point drive it is always the bottom limit switch which has to be proven, the contacts of these switches are included in the ‘NW’ and ‘RW’ control paths.

* Lever Bands :-The detection of the position of the lever in the frame is an essential requirement for the correct operation of vital circuits as in below figure. The different positions of lever bands is in correspondence with lever position.

Railway Remote Route Secure | Remote Securing in Existing System:

1. Remote securing shall be selected to provide an alternative indication at a particular signal which is prevented from being permissive through equipment failure.

2. The indication shows that the points to be traversed on the associated route have been locked and detected in the correct position, and will be held so by route locking.

3. This indication shall be used as part of a procedure to authorise slow-speed train movement when the signal has failed to reach a permissive state.

4. Remote securing of points shall continue to function in the event of a train detection failure, wherever possible.

Operation in Existing System:

1. The Signalman provided with a push-button that operates special relays, effectively locking the points. Successful locking results in a special indication being given to the train driver.

2. This takes the form of a white illuminated sign with the legend ‘Route Secure’ displayed at the signal controlling the entrance to the route.

3. The driver is instructed to pass the signal at danger and proceed at caution.

4. Where remote securing can be applied to more than one route ahead of a colour light stop signal, then more than one indicator will be provided.

ROUTE SECURE IN TBTC SYSTEM:

1. Route Secure Indications will be provided for Restricted Manual mode train moves over points and past floodgates.

2. The illuminated RS indicator will indicate to the train operator the unique path the train will follow: RS1, RS2, etc. When the RS indicator is illuminated, the point will be correctly aligned and detected (flank point detection is not required; however the VCC does reserve the flank point regardless) and will not move under or ahead of the train within the bounds of the RS move.

3. Restricted Manual trains can travel through points that are under manual control following Route Secure indications. These modes of operation would only be used in failure situations.

4. A Route Secure (RS) indicator is commanded to be lit or not lit by the SCS, after the required route has been set up.Setting of an RS at SMC or VCC

5. The RS move can be set up by a manual route reservation (MRR) or Route Secure Reservation (RSR) request to the SMC. The SMC will send the MRR/RSR request to the VCC and the VCC will reserve the tracks, points, conflict zones(CAZ), Border CAZs including an overlap for the manual train.

6. An MRR or RSR can also be command from the VCC at any time, including SMC failure.

7. When all the points have been successfully aligned, and other conditions at the site are correct, such as staff protection key switches normal or an indication from an external control systems (depots) that externally controlled points are locked and set, the command will be send from VCC to SCS to illuminate the RS indicator.

8. If RS is illuminated within a MRR or RSR for a train, the VCC will automatically cancel the RS indication when: – the front of a communicating RM train is reported to be at least 2 positions (inductive loop position) beyond the RS indicator when the move is part of an MRR; – an Non communicating train (NCT) is detected to have entered the block downstream to the RS indicator when the move is part of MRR; OR

– the train has been detected as having moved through the move when the move is part of an RSR.

Setting of an RS at LCP / DMC:

1. Upon the VCC failure, the points are required for RS route can be set individually to the correct direction by manual input of commands from the Local Control Panel (LCP) / Degraded Mode Control(DMC). It will be necessary to set each point separately by command through the LCP/DMC and then to command the RS sign to light.

2. Once the LCP or DMC command is issued to illuminate as RS sign, the SCS will evaluate that the current point settings within its area of control from a valid RS move, no staff protection key switches are set that inhibit the RS move, no opposing or conflicting RS indicators are set with in the SCS’s control area, the RS move is not blocked by a neighbouring SCS.

3. If the first criteria is not met, the SCS will reject the LCP or DMC command and operator will be notified of the rejection.

4. If the first criteria is met , the SCS will block its neighbouring SCS from setting an opposing or conflicting RS move and then the originating SCS will output the request to the SCS Relay Rack to illuminate the RS indicator.

5. If the site is under control of LCP or DMC or there are certain axle counter problems the RS moves must be manually cancelled.(from LCP, DMC, SMC or VCC as available).

6. Slow to drop output relays keep the RS illuminated if the SCS changes over from INTERSIG A to INTERSIG B.

7. Because the SCS only commands ‘lit’ or ‘not lit’, the relay rack is required to select the RS aspect based on the detected position of the points in the route.

8. The points appropriate to normal signal clearance are proved in the SCS, but only those point ends which the train runs over up to the next signal (excluding non-powered trailing points) need to be set, locked and detected in the correct position before displaying the “Remote Secure” indication.

9. Once the SCS commands the RS to light, if the initial conditions (i.e. point detection) are lost the SCS does not switch off the RS. The relay rack has to do it.

10. The SCS (either INTERSIG A or B) commands the RS to be lit, and the relay rack selects the aspect (based on 10 points normal or reverse, in this example).

Note:
1. ESP activation will not have any affect on Route Secure aspects.
2. The Track Circuit Interrupter will not have any affect on Route Secure aspects.

RS Symbol shown in SSP:

ROUTE SECURE INDICATOR UNIT

ROUTE SECURE INDICATOR UNIT, TYPES AND CONFIGURATION

ROUTE SECURE INDICATIOR UNIT, TYPES AND CONFIGURATION