LC gate interlocking method – I

1. The level crossing annunciation relay (LCAR) is kept normally energized in the gate lodge when no route over the level crossing has been set.

2. Any route is set, the concerned ASR/TRSR/TLSR drops which in turn de-energizes LCAR.

3. This causes the road signal on either side of the level crossing to display red aspect and the bells also start ringing.

4. The Gate-man closes the gate and locks it, by taking out the key.

LC gate interlocking method II

1. SM communicates to the gateman on phone to close the gate.

2. The gateman closes the gate, locks the boom and extracts key.

3. The gateman inserts the in key in EKT and turns it clockwise to transmit control.

4. There by LXR relay energizes & sticks through its own front contact.

Energisation of LXR relay at gate lodge energizes LXCR at relay room.

* With LXCR energized, through LXPR back contact B12 flasher supply gets connected to LXK(w) indication and it starts flashing on the panel.

* Then SM acknowledges by turning the LC control knob to normal.

The moment LX22 knob is  normalized, LX22 RR drops.

Through LX22 RR drop & LXCR up contact, the 22 LXPR picks up, then SM clears the signal.

Through LX22 RR drop & LXCR up contact, the 22 LXPR picks up, then SM clears the signal.

* The moment signal is cleared, the ASR concerned drops which ensures the 22LXFR to drop.

* There by as long as the signal is in taken off condition, LXYR does not pick up and there by gateman cannot open the gate, even if SM inadvertently turns the LC control knob to reverse.

Interlocking of Level Crossing Gate, LC gate interlocking method – I, LC gate interlocking method – II,LCAR, Gateman, LXR relay, LC control knob

At HR stage all the conditions to be satisfied for clearing a signal are proved.

• Crank handles are ‘in’, i.e. proved by CHLRs up and CHFRs down.
• Route Release Relays have de-energized after the last train movement i.e UYR1, UYR2 etc., are down.
• No cancellation is initiated i.e. JSLR down.
• Interlocked LCs if any in the Route and overlap are locked and closed against Road traffic (LXPR up) and held locked till the passage of that train is over.
• Conflicting signals are at ‘ON’ is proved by proving the front contact of ASRs or back contacts UCRs of conflicting signals.
• All points in the route, overlap and isolation are set and locked i.e. Concerned NWKRs, RWKRs are in up condition.
• Concerned to its own signal i.e

      –     RR is up

      –    UCR is up

      –    ASR is down

     –    One signal – one train feature (TSR up)

* All Back lock & and controlling tracks are clear i.e. TPRs concerned are up.

* Signal ahead is not blank (GECR up or RECR/HECR/DECR UP)

* Route Indicator lamps are not lit for straight line (UHRs / UGRs and UECR down) compulsory in case of Junction type Indicator

* Route Indicator lamps are lit for loop lines (UGR or UHR and UECR up)

* Sidings in the route & overlap are kept normal and held (siding KLPR/NPR up).

* Cross protection is provided for the signal control relay, by the Front contact of ASR or Back contact of UCR.

* Double cutting is provided by UCR up & ASR down

HR CIRCUIT FOR S1

POINT NCR/RCR  Circuit

* NCR is energized for normal operation of point when point knob is turned to normal.

* RCR is energized for reverse operation of the point when point knob is turned to reverse.

* The normal and reverse contacts of knob are bridged by SMR back contacts, thereby point remains in last operated position when the SM locks the panel.

* Either NCR or RCR always remains in energized position till the point knob is turned to the other side.

WLR CIRCUIT

* WLR is normally a de-energized relay. So normally the point is locked electrically.

* WLR relay gets energized whenever the point knob is turned from R to N i.e. NCR energized or point knob turned from N to R i.e. RCR energized, provided all other conditions are satisfied.

* When the point is set and indication relay is energized, drops the WLR and locks the point electrically.

* In WLR circuit, all the signal ASRs in whose route that point is included, are proved in up condition.

* All OVSRs for that point are proved in up condition.

* Track locking is proved by its point zone tracks.

* Track locking is bypassed by its own WLR front contact as stick path. So that once a point movement is started, it completes its operation even the track down occurs during operation. In some railways crank handle ‘IN’ is also proved.

* When ever the signal is taken off, the concerned ASR drops and locks the point i.e. it does not allow WLR to pick up  though the point knob  is turned.

WLR CIRCUIT

PCR CIRCUIT

With WLR up, the PCR  heavy duty relay picks up

With PCR up 110v DC  is extended to point location.

NWKR/RWKR CIRCUIT

* With WLR, RCR/NCR picked up, NWKR/RWKR drops.

* There by all indication relays& its repeater relays (NWKPRs, RWKPRs, NWKSRs, RWKSRs) drop.

NWR/RWR CIRCUIT

With WLR up, all indication relays drop, NCR/RCR up, NWR/RWR will pick up at location

POINT OPERATION CIRCUIT AT LOCATION

* With NWR/RWR picks up, WJR picks up.

* There by WXR picks up and sticks with its own front contact.

* With WXR picking up, normal feed to WJR removed but WJR held in pick up through time delay condenser circuit.

WCR CIRCUIT

• With WXR, WJR, NWR/RWR up and WNKR/WRKR drop, WCR (QBCAI relay) picks up.

POINT OPERATION

• With WCR & NWR/RWR up, 110V DC available on bus bar is extended to point machines at A end & B end parallelly.
• Both points are set to Normal or Reverse.

WNKR/WRKR CIRCUIT

• There by WNKR/WRKR picks up.

NWKR/RWKR CIRCUIT

1. Energisation of WNKR/WRKR results in dropping of WJR, WCR, and NWR/RWR.

2. With NWR/RWR dropping, WXR drops.

3. Due to all controlling relays (WCR, WJR, WXR, NWR, RWR) at location dropping and WNKR/WRKR picking up, energizes indication relay NWKR/RWKR at relay room.

NWKR/RWKR CIRCUIT

1. Energisation of WNKR/WRKR results in dropping of WJR, WCR, and NWR/RWR.

2. With NWR/RWR dropping, WXR drops.

3. Due to all controlling relays (WCR, WJR, WXR, NWR, RWR) at location dropping and WNKR/WRKR picking up, energizes indication relay NWKR/RWKR at relay room.

POINT OPERATION

1. Energisation of NWKR/RWKR results in dropping of WLR and locks the point electrically.  

2. De-energisation of WLR in turn drops PCR1 /PCR2, thereby 110V DC is withdrawn from the location bus bar.

3. In nutshell it can be concluded that point operation initiated, point unlocked, point operated & set, all point controlling relays de-energized, point indication obtained and point locked again.

NWKR/RWKR, NWR/RWR, POINT OPERATION CIRCUIT, WCR, POINT OPERATION, WNKR/WRKR, NWKR/RWKR CIRCUIT 

Introduction
1. A Track circuit is an Electrical circuit of which the running Rail of a Railway track forms a part. It is employed for indicating the presence of Trains and thereby for controlling Signalling and Block equipment. For the device Track circuit, the following truly holds good.

2. ‘No single Invention in the history of Development of Railway Transportation has contributed more towards Safety and Dispatch Control in that field than the Track circuit. Track circuit forms the foundation for the development of practically every one of the intricate Systems of Railway Signalling in use today wherein the Train itself is continuously active in maintaining its own protection’

3. Track circuits are categorized as DC Track circuits, AC Track circuits, and Electronic Track circuits (AFTC).

Railway Signalling DC Track Circuit

Open Loop DC TC: The circuit gets completed when the track is occupied through the net resistance of the vehicle axles occupying the track circuit. The series resistance is so adjusted as to give sufficient voltage to the relay when track rails are shunted by axles. In this type of track circuit, if any connection breaks, its occupation goes undetected. Hence, it is used only for limited purposes where its failure does not lead to unsafe conditions.

What is a Closed-Loop DC track circuit?

In this track circuit, the series resistance is called a Regulating Resistance. It regulates the relay voltage so that it falls below the drop-away value when the track is shunted. The fall is caused by the increased voltage drop across the regulating resistance due to a rise in-circuit current when shunted by the vehicles.

What is an AC track circuit?

A.C. Track Circuits are provided exclusively in DC traction areas confined to Bombay Divisions of Western and Central Railways. It is possible to work A.C. Track circuits with A.C. traction also, provided the track circuit supply frequency does not have even a harmonic relation with the traction power frequency of 50Hz. 83 1/3 Hz frequency is chosen for this purpose and these track circuits are used in A.C. Traction areas including the places where DC electric traction ends and AC traction starts.

AC Track Circuits is two Types:

1. Single Rail AC Track Circuits

2. Double Rail AC Track Circuits

The length of the Single Rail Track circuit is permitted up to 500 meters. The maximum permissible length of the Double Rail Track circuit is 2,300 meters. The cable lead Resistance at the Relay end shall not exceed 12 Ohms irrespective of the length of Track circuits. The feed end cable Resistance shall not exceed 12 Ohms for Track circuits of 2,100 and 2,300 meters and it can be progressively more with reduction of Track circuit length.

AFTC

• The Audio Frequency Track Circuit (AFTC) is the Jointless type of track circuit
• specifically designed to meet the onerous immunity required in AC or DC electrified areas
• against the high levels of interference present mainly due to traction harmonics.
• The equipment is classified as universal since it can be used in AC, DC, or Non-electrified sections and meets all the requirements of the known track circuits.

SDTC

• The Smartway DTC is a solid-state, fail- safe system which performs, in a safe way, the train detection, rail continuity detection and track to train data transmission functions within a track circuit (TC) using audio frequency signals

Technical Specifications

• TC length: from 20 to 400 m;
• Transversal conductance: from 0 to 0.5 S/km (2 ohm∙km), LTC=400 m;
• from 0 to 1 S/km (1 ohm∙km), LTC=320 m;
• Maximum shunt resistance 0.5 Ohm;
• Overlap length 7 m (joint length);
• Maximum distance between SER and track connections
• 4.5 km if LTC=350 m, Ballast 0.5 S/km (2 ohm∙km);
• 2.0 km if LTC=400 m, Ballast 0.5 S/km (2 ohm∙km);
• 4.5 km if LTC=280 m, Ballast 1 S/km (1 ohm∙km);
• 2.0 km if LTC=320 m, Ballast 1 S/km (1 ohm∙km)

• Cable type 2×1.5 mm2, 40 nF/km, shielded;
• Data transmission speed: 400 bit/s for train detection;500 bit/s for Sacem;
• Rail continuity control throughout track circuit; Yes
• Maximum number of points in TC 2;
• Power supply 220 Vac ±10% at 50 Hz to 60 Hz;
• Temperature range -25°/+70° in the SER; -40°/+80° in the field;
• Frequency carriers (8nos.) 9.5-11.1-12.7-14.3-15.9-17.5-19.1-20.7 kHz;

• Modulation: MSK ±100 Hz at 400 bit/s (Digicode TC)
• : CPFSK ±100 Hz at 500 bit/s ( data);
• Vital Output 12 Vdc on 400 W or 24 Vdc on 1600 W, insulation 1000 Vac;
• DOT 24 Vdc on 1500 W, insulation 1000 Vac;
• Diagnostic RS232 front or RS422/485 rear connector, at 9600 bit/s, packet
• data protocol.

Frequency and codes arrangement

Electrical Joints

Electrical Joints, S-Bond

Electrical Joints, Type S-Bond

Electrical Joints: terminal Bond

1.Single rail insulation:- Terminal bond allows delimiting the track circuit at a boundary with an Insulated Rail Joint as shown on
Figure The traction current can continue on the next track circuit by flowing through the terminal bond.

2. Double rail insulation:- Terminal bond allows to delimit the track circuit at a boundary with an Insulated Rail Joint on both rails as
shown in Figure.

ELECTRICAL JOINT, TYPE: DOUBLE ALPHA (TERMINAL ) BOND

ELECTRICAL JOINT, TYPE: DOUBLE ALPHA (TERMINAL ) BOND

INSULATED RAIL JOINT

Electrical Joints: Short circuit Bond

Short circuit bond At a boundary with an area without a track circuit, a short circuit bond can be used as shown in Figure
This configuration does not require any Insulated Rail Joints but the drawback is a dead zone whose length is in relation to the limit shunt value.

SDTC principle

SDTC: specific installation: S Bond in crossing

   Please Watch this Video:-   https://youtu.be/76XWS4EEPWw

Combined Indication & control panel

Station Layout

Point setting and locking sequence

RRI-Free wired Route Setting

Availability of selected route

The control table specifies the controls required for route setting Generally when the route is initiated the following checks are made to confirm that the selected route is free to be called.

Checks-
1. Points including overlap and flank points are either already set to the required position or free.
2. Directly opposing route not set.
3. Conflicting routes are not initiated.
4. Other routes of the same signal are not initiated.
5. Any other special conditions required.

Route Lock relays

1. Each route is provided with a pair of route lock relays NLR/RLR
2. NLR is a magnetically latched relay(BR935) –
3. It is having two windings.

4. When a route is released PU winding gets to feed and the relay picks up.
5. It gets latched in even after the feed is disconnected.
6. This is the normal condition and indicates the route is free

7. When a route is initiated the other winding gets to feed and the relay gets de-latched.
8. This prevents any other conflicting or directly opposing routes are being set. RLR is a neutral relay
9. RLR is a neutral relay, normally de-energized

10. Energises when the route is set.
11. De-energises when the route is released either by normalization of route e or by TORR.

RLR/NLR circuit

1. Each circuit comprises two parts.
2. Left side of the coil called positive path.
3. Right Side of the coil called the negative path.

4. Pushbutton commands (S)R & (D)R etc. are proved on a positive path.
5. All route controls and special conditions are proved on the negative path.

Route controls are mainly three types –

Opposing Locking – opposing routes with the same setting points. Front contacts of opposing routes and front contacts of opposing USR of route section past the signal are proved.

Point Selection  – all points in the route including flank points and points in overlap are either already set to the required position or free to move. other routes starting from the same signal are not locked out.

Route initiation circuit

Relays in point control

Point status

Points normal or free

Points reverse or free

Points normal and locked

Points reverse and locked

Points called to the required position

Point control and detection circuits

SIGNAL BUTTON CIRCUIT
Any button pressed, the concerned signal button relay will pick up providing all other buttons relays are dropped and no button remain pressed.

ROUTE BUTTON CIRCUIT

Required route button is pressed to energize the route button relay

POINT BUTTON CIRCUIT
When the point button WN is pressed concerned WR will pick up proving all other point buttons are normal.

COMMON GROUP BUTTONS CIRCUITS

NNR CIRCUIT
NNR is a normally energized relay and proves that the signal is at `ON’ and normal.

* NRR picks up through conf. NNR’s pick up and GNRR(GNR) & UNR pick up. The button relay contacts are bypassed with its own pick up contact. 

* On the negative side it picks up through EGGNR drop contact bypassed by GNRR drop contact. The sequential route release relay UYR2/UYR3/UYR4 drop is also proved on the negative side.

* NRR drops as soon as train passes the signal and UYRs pick up or when GN & EGGN button are pressed simultaneously to pick up GNRR & EGGNR to cancel the signal .

NLR/RLR CIRCUIT

NRR CIRCUIT

NLR/RLR CIRCUIT

All this NRR’s of all signals and overlap are used to pick up concerned point NLR/RLR relays for operating of points to the required position as per the signal Route.

Every point will have one NLR and RLR each.

NLR and RLR are numbered with concerned point No. and they pick up WNR or WRR which in turn initiates point control and operates the point to normal or reverse respectively.

0VNNR

OVNRR

WNR/WRR CIRCUIT

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RRI Signal, Points With Switches & Routes With Buttens

ANR/BNR CIRCUIT

When route button is pressed, the route button relay concerned ANR , BNR etc. picks up.

RR RELAY

RR RELAY: WHEN THE KNOB REVERSED, THE RR CONCERNED PICKS UP PROVING ALL OTHER CONFLICTING SIGNALS NRs IN PICKUP

LR RELAY

• As the signal knob is reversed and the route button is pressed, the LR concerned picks up by proving all other conflicting route LRs in drop and conflicting  ASRs in pick up.

• Once LR pickup it sticks through its own front contact

NCR/RCR

• Depending upon the route to be set , the concerned point NCR/RCR( WNR/WRR  in some railways) will energize through NC/RC contact & WLR pick up contact.

• The moment NCR/RCR picks up , the rest of the point operation is exactly similar to the non-route setting type  panel  point operation.

• In this way all the points required for the signal route will be set automatically.

NCR/RCR CIRCUIT

RRI Signal, Points With Switches & Routes With Buttens,ANR/BNR CIRCUIT,RR RELAY, NCR/RCR,  NCR, RCR CIRCUIT