Notes On Relay Interlocking (iriset)

CHAPTER 1

S5J1

INTRODUCTION 1.1 This system of Route Relay Interlocking was first installed in India at Basin Bridge Junction and Madras Central Stations of Southern Railway and was designed by the Nippon Signal Co. Ltd., Tokyo, Japan. This was followed by the installations in the suburban stations including Metre Gauge terminal stations like Bangalore City. Due to the simplicity of the circuits employed and the indigenous manufacture of almost all the components required for the system in the Railway owned Workshops, this system of RRI is popular in Southern Railway and South Central Railway. Such a system also exists in South Eastern and North Eastern Railways. 1.2

BRIEF DESCRIPTION OF SYSTEM:

This system is based on a geographical layout of signal switches and push buttons. All that is required by an operator to move trains is to know where a particular train is and to which line it has to be routed. Therefore, to set up a particular route, the operator is required to perform some action on the geographical layout of Control Panel at these two points, viz., at ENTRANCE and EXIT. In British system, these two actions take the form of turning a switch at the entrance and pressing a button at the Exit, of that particular route. For this reason, the system is known as “Entrance – Exit System “ or “NX System” in short. This conforms to IRS Specification .IRS – 36/87 and Correction given in 96. 1.3 CONTROL PANEL: All the points and signals are operated from a combined indication diagram cum control panel located in the cabin/Station Masters Room. The combined indication diagram cum control panel consists of an inclined console on which a clear geographical representation of the entire track layout with signals, points, Control switches, push buttons and various types of indications and alarms available. The track layout is sub-divided into track sections according to the track circuit configuration with distinctive colour for each track circuit section. (All colours except Red). On the track, adjacent to each signal there is an “Entrance Thumb Switch” at the centre of the track of the route, an “Exit push Button”. The Exit button is coloured white with alphabets engraved on it. The entrance switch is coloured Red for running signals and Yellow for shunt signals with the number of the relevant signals engraved in the centre of the switch. The king knob used in semi-automatic territory is coloured red with a white bar across the knob. There are two types of signal switches, one turning 900 towards right and the other turning 900 towards left. Normally, the switch knobs will be at right angles to the track and when turned they become horizontal, the knob pointing towards the direction of the train movement that has to take place. Push button restores to normal when released. In addition to Signal switches, 3-Position point thumb switches coloured black are provided, one for each set of points for individual operation of points Calling ON Signal switch is coloured Red with white dot and crank handle releasing switch is blue in colour. Similarly level crossing control switch is coloured in deep brown. When a route is set and locked, the route is illuminated by white strip lights in the track circuit configurations throughout the route (except the overlap). This indication remains lit as long as the route is locked and disappears only after the relevant signal switch is restored to normal position and the route is released. This indication turns to Red when track is occupied or track circuit failed, irrespective of whether the route is locked or free. When the speed and frequency of the trains are to be increased, Relay interlocking is ideal. In Relay Interlocking the Interlocking is achieved through relay circuitry at a centralised place. The time required for installations is also less. The Relay Systems are generally trouble free since 1

the moving parts involved are less and replacement is easier. Indian Railways are having time tested experience in Relay Interlocking since 1958. Route Relay Interlocking is a system in which Interlocking is achieved by means of Relays. In British system the relays confirming to BRS and BSS specification, having metal to carbon contacts are used, (Q Series Relays). Therefore, the circuitry becomes comparatively simpler as welding of contacts need not be considered.

Fig. 1.1 1.4

SEQUENCE OF OPERATIONS:

The sequence of operation of the equipment is explained with the help of a block diagram (Fig. 1.2) Turning the entrance knob and pressing the exit button of a route, energises the route selection relay (LR), provided that no conflicting route is set. Thus the basic interlocking is ensured at the first stage itself. The energisation of the route selection relay picks up all the point control relays (WLRs) in that route depending on the route selected provided that the points are free from track locking and route locking. The point control relay, controls the point machine concerned and sets the points required in the route. The correct setting and locking of each point is indicated by the point indication relay (NWKR/RWKR). The route checking relay (UCR) checks that all the points involved in the selected route are correctly set and locked at the site. It also proves that the route set is for the Signal route initiated including isolation and overlap. The operation of the route checking relay (UCR) de-energises the relevant approach stick relay (ASR) and sectional route locking relays (TLSR/TRSRs) thereby ensuring that the complete route is locked before the signal is cleared. The signal Control Relay is energised proving all safety conditions required viz., all tracks, including overlap are clear, all points, including those in overlap, isolation, are correctly set and locked, relevant route locking and approach locking relays are de-energised etc. In addition a control by track stick relay is used to ensure that the signal does not re-clear after the passage of a train as the relevant thumb switch is left in the operated position. The control by the track stick relay is removed if the signal has to work as an automatic signal, by the operation of king knob relay, which is energised by the reversal of the king knob.

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3

The approach stick and sectional route locking relays will re-energise when the train arrives & clears the route and the signal switch is turned to Normal Position. Sectional release of route is, of course, provided wherever necessary. In British System, after the arrival of a train on proper signals, route gets released only after the normalisation of concerned signal knob by the operator provided all other conditions are satisfied. Since the Route is released with the knowledge of Station Master, the overlap will be released immediately, as soon as the Route is released. In British System holding of overlap for certain time delay (120 minutes) is not considered mandatory. 1.5

REQUIREMENTS OF RELAY INTERLOCKING

Guidelines for the Design, Installation and maintenance of Relay interlocking SEM Para 7.82 & 7.83 of new edition. G&SR Chapters 3,5,8 and 9. Specification No.S-36/87-96. Section K of Ch.VII of 1988 SEM for Relay interlocking installations (Route setting type). The specification No.S-36/87 deals with the requirement of Relay Interlocking in general. Relay interlocking systems are popularly divided as Route setting type (RRI) and Non route setting type (panel interlocking). The features of Relay Interlocking in general are as follows. The RRI will have the additional facility of automatic operation of all points in route, overlap and isolation with a single command by Entrance-Exit System. 1.6

FEATURES OF RELAY INTERLOCKING. • • • • • • • • • • •

• • • • • • •

All operations are controlled from a Control panel by the operator. Knobs are provided for operating signals and points and they will bear the same number as the functions indicated in S.I. plan. In RRI points will have three position knobs (N, C, R). All other knobs in PI and RRI will have two positions generally (N,R). In RRI, Push buttons (self-restoring type) are provided for each route/overlap. They are numbered alphabetically. Relays with metal to carbon contacts are used in general. Colour light signals are provided. Yard is Fully track circuited, between home to home signals in single line and Home to advanced starter on either direction in double line. Approach track is optional. Crank handle, Level crossing, siding interlocking etc. are achieved through EKT /RKT/Lever locks. 16 strands of 0.2 mm dia PVC Flexible wire is used for inter relay wiring. The Relays are neutral and not latched ones. No interlocked Relays are used . Hence normally power supply requirement is comparatively higher. A few vital relay circuits are kept energised by means of stick path; battery back up is required. The idea of keeping such vital relays energised is to comply with the principles of closed circuits. In case of failure the relay drops, failure will be on safe side only. 12V, 1.2W pencil type lamp or LEDs are used on the indication panel to indicate various indications on the operating panel. Different colours are obtained through jewels of different signal aspects. Hence common white indication lamp is used or coloured LEDs are used. For signal lighting of 110VAC, stabilised supply is used to increase life of signal lamps. 110VAC for track feed Battery chargers are used for Track circuits. 110VDC for point operation and for inverter wherever UPS for signal lights is provided. 24 VDC for Q Series Relay.- Internal and External Seperately. 12 VDC for QS-3 – Relay in Axle Counters and EKTs. 4

• • • 1.7

12 VDC/AC for panel indications. The DC supplies are generally derived from a battery source, which is charged by a battery charger on float. Stand by power supply is provided from a D.G. set or from traction supply. Features of operating PANEL

All signals are provided with Rotary Switch / knobs with indications aspect - wise at their respective position. Route indications are also repeated route wise on the signal configuration. All points are provided with 2 position knobs (Three position knobs in case of RRI) with N, R indications (Normal Green / White Lamp and Reverse Yellow / Green Lamp.) Track circuit occupied /failed indications are also given in Red Colour. LCs, Sidings, etc. are also controlled by knobs with indications on the control cum indication panel. When Route is set and locked ‘white’ indication appears on the route portion. Normally in British panels over lap is not lit though OV is locked. As already explained interlocking of every function associated with the signal clearance, Point. Operation, level crossing interlocking, Crank Handle interlocking, sidings interlocking etc are achieved through Relay circuits. The sequence of operation of Relays and various stages of circuits are as follows. Note:- Before going for PI/RRI it is necessary to ensure reliable and stable power supply for smooth working after commissioning. Comparison of RRI and PI : Route Setting Type (RRI)

Non Route Setting Type (PI)

1. Automatic Route setting facility is available, which means that with single command, points in the Route, Overlap and Isolation can be operated to the required condition.

1. Automatic Route setting facility is not available. Points have to be operated individually for setting the Route.

2. RRI is adopted for bigger yards generally.

2. PI is adopted for smaller yards.

3.

Provision of compulsory.

Colour

light

signalling

is 3. Colour light compulsory.

4. Sectional route release facility is compulsory 5.

Points are operated with 3 position pt.Knobs.

signalling

is

4. Sectional route release facility is not compulsory

5 Points are operated with 2 position Knobs. 6. Separate point Lock/Free indication is not 6. Separate point Lock/Free provided. indication is provides over the point knob. 7. Route Button is provided on the berthing Track 7. Route Button is not (For Entrance & Exit Operation ) Compulsory since it is not NX system.

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Note :- As per latest IRS-S-36/87 CLS and motor operated points and operating panel are compulsory with track circuits from home to home.

CHAPTER – 2

S5J1

SEQUENCE OF OPERATIONS The sequence of operations involved in British RRI are indicated in the Block Diagram given at Fig. 1.2. 2.1

STAGES OF SIGNAL CLEARANCE: -

The stages of Signal Clearance will be as follows: For Clearing a signal, only authorised persons can make operations. This is ensured by providing a SM key on the control panel. With SM key is ‘IN,’ SM turns signal knob and presses route push button and releases. This is called route selection. A relay called “LR” will pick up which in turn operates the points in Route, overlap and isolation to the required position if the point is free to be operated or the point is not engaged by any other route, and the point zone is not occupied by train. The relays NWKR/RWKR picks up when points are correctly set and locked at site. Once if the points in the route are operated, i.e., the route is set and locked. (as per New SEM para 7.27, the route is to be checked.) For route checking the relay called UCR picks up. Every signal will have one route checking relay (UCR) and it ensures NWKR/RWKRs of points in the route, overlap and isolation etc., and other conditions such as knob reversal by authorised persons etc are incorporated in its circuit. After checking, the route has to be locked. Route Locking means, holding the point in the route and overlap in locked condition, after the clearance of signal. A relay called ASR’ is employed for this purpose. Normally this relay will be in picked up condition. When route is checked i.e. when the UCR picks up, ASR drops. When ASR drops, another relay called point lock relay (WLR) also drops. When WLR drops, point cannot be operated. Now the ASR picks up only when the train has arrived on proper signal with sequential operation of track circuits or if the route is cancelled ensuring back locking, Indication locking and approach locking. The details of back locking, indication locking and approach locking etc: have already been discussed in the topic SELECTION CIRCUITS (S5H). For clearing signal, Signal control relay called HR is energised. For a detail study a 3-Road typical station layout as shown in Fig.3 is taken and typical circuits are dealt in detail along with explanation, for the same layout.

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Fig.2.1 1.2

Conditions for clearing a fixed Signal.

(I)

All concerned points are correctly set and locked wherever required as detailed below. (1) (2) (3) (4)

For Home Signal, points in the route, in isolation & in overlap. For starter signals, Points in the route, in isolation. for shunt signals, points in the route (Isolation is not compulsory) for calling on signal, on single line, points in the route, in isolation & in the overlap and on double line, Points in route & in isolation.

(II)

Whenever points are operated by Point machines it shall be ensured that the concerned crank handle (S) is/are kept locked in EKT/HKT.

(III)

All concerned Track Circuits are clear as detailed below: -

1.3

(a)

For Home signal: - Track Circuits in the route, concerned berthing Track Circuit and overlap track circuits.

(b)

For starter signal: - Track circuits upto next stop signal in advance.

(c)

For shunt signal: - All Track Circuits in the route normally up to next stop signal in the route, except berthing track circuits. In big yards up to intermediate shunt signal if any.

(d)

For Calling on Signals no track in advance need to be proved but it shall be capable of clearing the Calling on Signal only after Calling on track is occupied and stipulated time (timer operated) delay is completed.

DETAILS OF RELAYS FOR SIGNAL CLEARANCE:

As already stated, following are the stages of Circuits • • • • •

SM’s key inserted and turned to ensure authorised operation(SMR/SMCR/SMPR up) Route initiation/selection is done (LRs up) by the authorised person. Route setting (operating the points to the required condition. (NWKRs/RWKRs up ) Route checking (UCR up) Route Locking/Over lap locking (ASR/TRSR//TLSR/OVSR down), Electrical locking of points.( WLR down)

In addition to the above, for Signal Clearance, the following conditions are also to be satisfied • • • •

• • •

The clearance of track in the route & overlap (TPRs up ) One signal - one train feature (TSR up) No cancellation is initiated (JSLR down) Route Release Relays have de-energised after the last train movement ( UYR1, UYR2 etc., are down) (In Southern Railways UYR1 and UYR2 are called as TSSLR and TPZR respectively) Route Indicator lamps are not lit for straight line (UHRs or UGR and UECR down) (compulsory in case of Junction type Indicator) Route Indicator lamps are lit for turn out (UGR or UHR and UECR up) 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. 7

• • • •

Concerned crank handles are `in’ and locked (CHR /CHLR up) Sidings in the route & overlap are kept normal and held (siding KLPR/NPR up) Aspect of signal ahead is displayed (GECR up or RECR/HECR/DECR UP) Cross protection is provided for the signal control (by the Front contact of ASR or Back contact of UCR ) These contacts are not favourable for signal clearance

Conflicting signals are proved either directly or indirectly by proving the front contact of ASRs of conflicting signals in UCR circuit of the signal to be cleared. Now every circuit will be discussed in detail separately. For explanations sake, small circuits relevant to the yard are given.

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CHAPTER – 3

S5J1

CONTROL TABLE For designing circuits of a yard, the `Table of Control’ (also known as Selection Table) is to be prepared first. The table of control provides necessary information for the preparation of circuits. It consists of the following information: • • • • • •

Details of signals with aspect Routes governed by signal The method for Route holding i.e. either approach locking with approach track circuits or dead approach locking with out approach track circuits. The back locking and controlling track circuits, crank handle grouping and aspect ahead of the concerned signal. The points in Route, Overlap and isolation which are detected and locked by the signals. The conflicting signal/Route locked by this signal Any other controls like interlocked level crossing, interlocked siding, lighting of Route indicators, Block control etc.

3.1 It is customary to send the selection table for CRS approval along with other documents. Selection table is a user-friendly data, which gives entire information about the inter- locking and various conditions for setting the route, holding the route and clearing a signal. The selection table is a basic requirement for testing various signals in a yard during commissioning and afterwards also. Each column of selection table is utilised for each circuit and for attending failures also for early rectification. Prior to designing of circuits, the selection table will be prepared by Drawing Office Staff. It will be checked by Chief Drafts man of Drg.Office and ASTE/DSTE before getting approved by CSTE. A typical selection table for the given yard is as below. [The details of selection table have been already covered in S5H.] EXERCISE: - Prepare selection table for the Signal and Points not covered in this table.

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10

CHAPTER - 4

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RELAY INTER LOCKING ROUTE SET METHOD (SYSTEM – I) CIRCUIT EXPLANATION Based on the Block Diagram and Selection table various circuits will be discussed now in detail. Let us examine how a signal is cleared. To clear a Signal, SM has to ensure that the following conditions are fulfilled. • • • • • • • • • •

The track circuits are clear. LC gate if any is closed Crank handles are ‘in’ and locked Knob of conflicting signals are normal Point knob is in centre position or in the same position of points required to be set Route is released after the last operation and not locked by any other conflicting signal. Point free indication, is available. SM key is `in’ and turned Line Clear obtained for LSS Time cancellation is not in progress.

If the above conditions are fulfilled then, SM starts the signal clearance. 4.1

SMR/SMCR Circuits.

When SM’S key is ‘in’ and concerned knob is turned SMR/ SMCR picks up. The front contact of SMR/ SMCR will be proved in various circuits to ensure the authorized operation of the panel.

Fig. 4.1 4.2

LR CIRCUIT

Route Selection Relay: LR is named after the signal and the Route for example, 1ALR has to pick up when signal 1 is leading to route 'A'. To clear a signal SM turns the knob.1 in the direction of a train and presses Route button A and then the concerned LR picks up. The LR is picked up and operate the points to the required condition. LR front contact is used in UCR and HR circuits also. LR is normally down and picks up only when there is an operation to clear a signal. LR picks up only when the conflicting LRs are down. Thus at the route selection stage itself, locking of conflicting signals is done. Once LR picks up, it sticks through its own front contact till the knob is normalised with SM key `in’& turned to ‘R’ Position. The back contacts of LR are included for locking the conflicting signals, which are directly opposing. In other words for those LR for which the point position are same are included. In addition to this, 1A2LR, 1BLR, 1C1LR, 1C2LR, contacts are also included to avoid picking up of 11

relays simultaneously with 1A1LR picked up with a single operation of a route button. At times it so happens that, the knobs 1 and 10 may be in reverse condition because there is no mechanical interlocking between knobs. At this position, if button A is pressed, there is a possibility of both 1 A2LR and 10 A2LR to pick up. This is not desirable. Similarly when knob is turned to pick up 1A1LR route button, if again B is pressed then 1 BLR also picks up since Knob operation is same for A&B routes. To avoid all these inadvertent energisation, back contacts of unwanted LRs are to be included judiciously. Now with all conflicting LRs down, A 1 button pressed contact and SMR up, 1A1LR picks up. The ALR front contact by pass the button pressed contact, as the same will not be available when SM releases the push button. The SMR back contact is bridged across the reversed contact of signal knob to prevent the de-energisation of LR when an un-authorised person normalises the signal knob, if SM has locked the panel.

Fig.4.2 4.3.1

POINT CONTROL CIRCUIT: (Combined WLR/WNR/WRR)

A point can be operated only when, i) ii) iii)

The point is not engaged in Route or Overlap of any Signal i.e., WLR is up. The Track Circuit of Point zone are free and track circuit is not failed i.e., ATR and BTR up. SM’s key is `in’.

Concerned LR should pick up with point Knob in centre position for automatic operation. The point knob should be turned to the required position (N/R) with all LRs dropped for individual operation. WLR (Point Lock relay). When WLR picks up it indicates that the point is free to be operated. The freeness of this point from route setting/overlap setting is indicated by the pick up contacts of ASR of all the signals which are leading over the point. Whenever sectional route release is provided, instead of ASR, TRSR and TLSR relay will be used to control WLR.

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The ASR circuit will be dealt in detail, but now it is to be understood that ASR front contact indicates that the Route is not locked by the concerned signal. In RRI, the point knob used is having three positions. The three positions of point knob are :Normal Reverse Centre At normal position N and NC contacts are made. At reverse position R and RC contacts are made. At centre position NC and RC contacts are made.

Fig.4.3

For the point to go to normal N or NC contacts should be available. For the point to go to reverse R or RC contacts should be available. The common contact which can allow the point to go to normal or reverse are NC and RC. Therefore, for automatic operation, the knob is always to be kept in centre position so that the point can go to normal or reverse according to the LR picked up with respect to the route. For the given yard, If 1A1LR picks up, point 101 goes to reverse and if 1BLR picks up Point 101 goes to normal. During route setting, after LRs picking up WLR picks up. Then WNR/WRR will pick up according to the route selected. When WNR picks up points go to normal and when WRR picks up points get operated to reverse. For points operation circuits please refer S5C, D, E notes. For individual operation, all concerned LRs will be in dropped condition and WNR/WRR picks up through (N) or (R) contacts of the point knob as per the position of the point knob. WLR, WRR and WNR circuits are shown in Fig.4.4

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14

4.3.2

HOLDING OF OVERLAP POINTS: 15

The Overlap Points can be held by proving the ASR front contact in concerned overlap point’s WLR Circuit. This method is not so effective as the Signal ASR will pickup soon after the back lock tracks are cleared by the train and the overlap points can be altered even though the train is still rolling down on berthing Track Circuit. (Assuming that Starter Signal is not taken OFF). To obviate the above disadvantage, an improved method of holding the overlap points is discussed below :-

Fig. 4.5  Where in a route if more than two over laps are available number of overlap relays are equal to no. of overlaps. overlap relay is nominated with the starter no. and overlap number. In this circuit, 3 OVSR relay will Pickup with 1 ASR front contact and 02A/B TPR front contact. This relay is normally energised. When Home Signal No.1 is taken OFF to Main Line (Road – 2), 1 ASR drops, thereby de-energises 3 OVSR, which in turn de-energises 102 WLR, locking the overlap points No.102. After the train arriving within the berthing track, clearing the back lock track circuits of Signal No.1, 1 ASR picks up but the OVSR relay is still kept de-energised as the train occupies 02A/BT. The OVSR relay gets energised only after the train clearing the berthing track circuits, if it is a run through train. Points No.102 are still kept locked as 3/5 ASR drops after Starter No. 3 is taken off for the run through train. If the train has to be stopped on Main Line berthing track and if precedence to another train stopped on loop line is to be given, Points No.102 are to be operated to reverse position but the Points are still locked as the train has not cleared 02A/BT. Under these circumstances, the OVSR relay will be energised through another path (3 OVJSLR and NJPR) which will be available after a certain time delay (generally 120 Seconds). 4.4

ROUTE CHECKING CIRCUITS - UCR 16

Once the points are set in the required condition, then the route setting is completed. The energisation of NWKR/RWKR indicates that points are set and locked after setting the route, it is to be checked. This is achieved by picking up UCRs (Route Checking Relays). The features of UCR circuits are as follows: •

One signal will have one UCR. UCR will be named after the signal.

•

This relay is normally de-energised and picks up when signal knob is turned and Route button is pressed, provided all the favourable conditions are available, viz.,

The points in the route, overlap and isolation are set and locked. To achieve locking of conflicting signals, Front Contact of ASRs of conflicting signals will be proved in UCR circuits Concerned LR front contact also will be proved in UCR Circuits. •

•

UCR front contact will be proved in HR circuit. UCR back contact will be proved in ASR circuit. This is utilised to drop ASR as soon UCR picks up i.e., to lock the Route as soon as it is checked. Back contact of UCR in ASR circuit also ensures that Signal knob is normalised before releasing the route. For checking the Route when the train is to be received on Road 2, SM presses button B and turns the knob 1, keeping all other knobs in normal and all point knob in central position. With this 1 BLR picks up. 1 BLR operates Pts. 101, 102, 103, 104 to normal and consequently 101 NWKR 102 NWKR, 103 NWKR picks up. Now the Route setting is over. After route setting is done, UCR circuit energises in the following manner. For energising UCR circuits, ASRs of conflicting signals are to be in pick up condition to ensure conflicting signal locking.

If the Route is to be set for Road 1, with overlap set to sand hump, 1A1LR has to be picked up and if overlap is set to main line 1 A2LR will pickup (number of route buttons depends upon number of sand humps. In this condition A2 is pressed for main line and A1 button is pressed for sand hump.) In either case 105 is to be normal to isolate the siding. 1UCR energies as shown in following diagram: UCR CIRCUIT

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4.5.1

ROUTE LOCKING CIRCUITS (ASR/TRSR/TLSR)

After checking the Route, it is to be locked. For locking the route, ASR to be de-energised. In ASR circuit, the following lockings are incorporated:• • •

Approach locking. Indication locking and Back locking

ASR stands for Approach Stick Relay. This Relay circuit is the most important circuit in British system of Relay Interlocking. The features of this circuit are as follows: The Relay is normally kept in pick up condition to comply with the principle of close circuit, which means that, if the Relay is de-energised due to, any reason it results in Route locking. ASR drops as soon as UCR picks up, since UCR back contact is proved in ASR circuit. When ASR drops, the WLRs of points concerned drop and points become inoperative. It is already understood that WLR should be in picked up position for any point to get operated. This is the reason why WLR is controlled by ASR and TPRs contact and WNR and WRR are controlled by WLR contact. It will be also seen that ASR and WLR back contacts will be proved in HR circuit to ensure that, both route and point are locked before signal is taken off. 4.5.2

ROUTE HOLDING:

From the principles of interlocking, we have understood the necessity of route holding. Route, here, means any thing that is protected by the signal and which is to be kept locked during the passage of train or during the approach of train. These include a point, or a level crossing. For ensuring safety of the train after giving signals it is necessary that the route should be held, 1. 2.

When the train is approaching and While the train is on the Route.

This means that, while the train is approaching the signal, it shall not be possible to release the route even if the SM tries for it intentionally or unintentionally. However, in centralised operations of signals and points the time of operation is very little and hence it is necessary to prevent the releasing of route while the train is approaching, with suitable circuits. In any case, the route is to be held till such time the train actually completes the journey over the route. For this a relay called ASR is used. The details of ASR have already been explained. Here it is important to understand that ASR has a dual role of locking the route and holding the route, before the signal is taken off. Now it is clear that route is locked and point is electrically locked before signal is taken off since ASR de-energised contact is proved in HR circuit. It is equally important to ensure that, the point to be negotiated by the train in route/overlap etc are not altered by anybody intentionally or un-intentionally. This can be prevented by restricting WLR from being energised. This is possible by not allowing ASR to pick up. Now we have to ensure that signal can be cleared only when ASR and WLR are de-energised. Once the ASR has dropped it cannot pick up i.e., once the route is locked it must not be released unless certain precautions are taken or conditions are satisfied which are indispensable to achieve safety. It shall not be possible to alter the conditions of the Route unless the signal has been first put back to on. 18

Let us find out the conditions required to be fulfilled before releasing the Routes. These are the conditions required for picking up ASR. They are: 1. 2. 3.

The Signal control Relays should be normal.(Signal & its dependent signal if any are at on ) This is achieved by proving the back contacts of concerned HRs, UHRs, DRs in ASR circuit. The signal control functions normal - normal contact of knob, back contact of UCR The signal should be at ON

This is achieved by proving RECR up. Since the bulb failure results in RECR failure, very often HECR, DECR, UECR back contacts are proved in ASR circuit. With this, we indirectly prove that signal is not OFF. However, where the signals are operated by signal machine, it is mandatory to ensure that, the signal arms are at ‘ON’ before releasing the route. The items No.1, 2, 3, together are known as indication locking. 4. The train has to clear the route i.e., the back lock TPRs are picked up. (As we know the route shall not be released when the train is on route). This condition is achieved by proving back lock track circuit relays in ASR circuit and is known as back locking. 5. The train should actuate the track circuits in the route sequentially. (Achieved by UYRs pick up contact) in case of train passing the route on signals (TSR down) or after a lapse of certain time delay.(achieved by NJPR up and JSLR or JR up), if the route is to be cancelled if the train occupied approach track but stopped in rear of the signal concerned. OR The approach track if any is not occupied (achieved by ATR up, TSR up) by the approaching train and TSR not de-energised. Once ASR picks up UYRs, JR, JSLR, NJPR, drops. Bobbing of track circuits and deenergisation of other associated relays shall not de-energise the ASR. This is achieved by providing a stick path through its own contact. The stick path by passes the back lock TPRs, normal contact of knob, UYRs/JR/ATR, so that after ASR picks up if any one track fails, ASR will not drop. ASR drops only when UCR picks up i.e., when route is checked. Let us examine the ASR circuits for signal No.1 referring our lay out. In the Circuit of ASR 101 AT is not required when point No.101 is normal. Therefore 101 AT is bypassed by 101 NWKR front contact. For similar reasons 102BT and 102 AT have also been bypassed. This is to avoid failure of ASR after the train arrival, when unconcerned track circuits failed.

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* Where sectional route release is provided in ASR circuit only first three track circuit are proved rest of the tracks provided with TRSR/TLSR. ASR made to pick up immediately after first three tracks clear and signal Knob is normalised. Fig.4.7 ASR CIRCUIT Now we will summarize the details about ASR ASR is normally picked up (through its own stick path) ASR when energized, indicates that the route is free / signal concerned is not taken off. Each signal will have one ASR or if a group of signals have common points and only one signal can be taken off at a time, as in the case of starters they may have a common ASR. ASR front contact is used in WLR, TRSR/TLSR, TSR and conflicting UCR circuit. To prove that a signal is not taken off, its ASR front contact can be used. This feature is used to achieve locking of conflicting signals. In fact ASR is the ideal relay to achieve interlocking between two conflicting signals. As ASR can pick up only when the train has arrived and cleared backlock tracks. ASR back contact is used to give route locked indication on the panel. ASR back contact is used in HR circuit to prove that route is locked before signal is taken ‘off’. ASR back contact is also used in picking up route release relays i.e., UYRs to ensure that, they pick up only when the train is arriving on proper signals. ASR back contacts are used in Timer circuits also to ensure that the timer is initiated only when the route is locked. 4.6

ONE SIGNAL - ONE TRAIN FEATURE CIRCUIT (TSR)

It may be seen that once the signal is cleared all the conditions will be available for the signal to assume OFF aspect again if the train has cleared the Route and overlap and the control for signal clearance has been kept in reverse position. This means that keeping signal switch in reverse the signal clears for many trains one after another automatically. This is not desirable in absolute block working. Therefore, a circuit is evolved to ensure that one train only passes on one signal clearance and after each train the route has to be released/lever to be normalised before the signal is taken off again, for the next train. For this, a relay called TSR is used.

Its circuit is given below: 20

Fig.4.8 TSR CIRCUIT Once signal is off, the train passes the signal and actuates 1 TPR (the first track immediately after signal and is called controlling track for this purpose). When 1 TPR drops, TSR also drops. ASR is already in de-energised condition. Now TSR can pick up only when ASR picks up and after signal knob is normalised. The next signal can be cleared again only when TSR has picked up as TSR pickup condition is proved in HR Circuit. Thus it is ensured that only one train is permitted on one signal clearance. Evidently this is achieved by proving TSR front contact in HR circuit When train passes signal, TSR drops. Therefore, front contact is used along with approach track circuit in ASR circuit to indicate that the train has not passed the signal while the approach locking is made effective to release the route. Similarly TSR dropped condition indicates that the train has passed the signal. Therefore, TSR back contact is used along with UYR relays for the normal route release path of ASR. TSR is made slow to release so that it does not drop in case of bobbing of track circuit. If TPR drops and signal goes to danger in the face of an approaching train, TSR cannot pick up as ASR front contact is not available. (If QSPAI relays are used as TPRS, the TSR need not be a slow to release relay) TSR is named after the signal, which it controls. TSR may be common if the track circuit is common for two or more signals. This arrangement is only to save the Relays. 4.7

PROVING OF THE ASPECT OF SIGNAL AHEAD (GECR)

In colour light signalling, there is a possibility of signal going blank due to lamp failures or power supply interruptions. This is undesirable since the Drivers are likely to miss the signal, which may result in an accident. To avoid this, it is a recent practice to prove the aspect of signal ahead in the rear signal. For example, for clearing a home signal, any one of the aspect of starter in advance will be proved. GECR is made slow to release to cater for the aspect changing of signal in advance.

* As it is, these contact combination may be used in HR ckt in place of GECR

21

Fig.4.9 GECR CIRCUIT 4.8

CRANK HANDLE INTERLOCKING CIRCUITS (CHLR/CHR)

Where points are operated by point motors, crank handles are provided to facilitate operation of points manually in case of electric operated point failure or for maintenance purpose. The manual operation of point, after a signal is cleared, may endanger the train operation. Therefore, it is necessary that crank-handle is interlocked with signals suitably. It is not possible to provide CH interlocking for every point individually. At the same time it is not proper to have only one crank handle common for all the points also. Therefore, points are grouped to achieve optimum flexibility. In our layout points are divided into three groups. CH1 group to cover 101 and 102 point, CH2 to cover 103 and 104 and CH3 to cover 105 i.e., when 105 has failed crank handle from CH3 HKT only will be taken out and signals No.Sh 13, Sh 14 S5,S10,CO10 to Rd.1,C1&S1will fail. Other signals will function normally.(Ref. Fig.2.1) Crank handle interlocking is done as shown in fig. No. 4.10 : Whenever a signaled move has to take place over the points it will not be possible to release the concerned CH which is kept locked inside an electrical key transmitter (HKT/RKT/EKT). When the crank handle is OUT it shall not be possible to: (i) (ii)

Operate the points from panel, and Clear any concerned signal.

For the above purpose, the crank handle is normally kept locked in an EKT and this condition (crank handle is in and locked) enables the crank handle Relay (CHLR/ CHR) to be energised. The crank handle gets locked, when the key riveted to it, is inserted in the EKT and turned to right. When the key is extracted, the relay CHLR drops and hence the signals interlocked with it cannot be taken off. To ensure that CHLR drops before the actual extraction of the key, the CHLR circuit is modified. When the economiser push button is pressed for extracting the crank handle, it breaks the supply to CHLR and CHLR drops. Unless CHLR drops extraction of crank handle is not possible. In the HKT, while the key is inserted and being turned contact No.1, 2 and 3, 5 will be made and CHLR will be picked up. Once the turning is over and the key is left, contact Nos.3& 5 will be broken. Therefore a stick path is provided to feed CHLR by passing contacts 3 & 5 with its front contact. . 22

Crank handle EKT will be kept locked in a glass fronted box provided with pad lock. The keys will be under the personal custody of S.M. S.M has to make entries in CH register whenever crank handle is released for the manual operation of the point. Instead of HR back contact ASR front contacts are used to ensure that Signals are at ‘ON’ for releasing Crank handle by certain Railways, wherever end panels are provided. In this case an emergency release system also is to be provided to release crank handle when ASR fails.

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4.9

SIDING CONTROL CIRCUITS. (SIDING NPR/KLPR).

Siding points may either be (a) operated from the panel directly or (b) operated locally but controlled by panel. Operation of siding points directly from the panel is resorted to, only if the movements over these points (into and out of siding) are frequent. In such cases these points are interlocked directly and also these sidings may be provided with shunt signals to control the movements. Where there are no frequent movements from/into the siding, then these points are operated locally, but controlled from the panel. The siding points remain locked in Normal position and the same can be released only when there is no signaled movement towards it. Siding points are also operated from a Ground Lever frame situated near siding point. Ground lever frame can be released only when the concerned 'E' type key, either physically brought from the panel room or transmitted electrically, is inserted in the Ground Lever. 'E' type key at the panel is extracted after reversing the siding control knob of the panel provided the concerned routes are normal. Where siding points interlocking is provided through electrical transmission of the 'E' type key, the following arrangements are provided. A pair of electrical key transmitters is provided one at the panel and the other at the siding in a location. The key at the siding remains locked in the EKT. The siding key in and locked the Ground frame lever normal are proved in the siding NPR circuit and NPR is proved energised in the concerned signal HR circuit. Thus these signals cannot be taken off if the key has been transmitted to the siding as NPR drops when once the key is extracted. To reduce the time taken for shunt movements over the siding point, the key is kept locked in the EKT inside a location box adjacent to the siding. EKT is energised through a relay, "Siding YR" which is controlled from the panel. Siding YR can be energised only when: i) ii)

The signals concerned are at 'ON' and the Respective siding control knob is reversed

When siding YR is energised free indication at the EKT appears and the siding key is released by pressing the economiser push. The siding key thus extracted is inserted in the lock on Ground frame lever and siding point is operated. After the completion of the shunt movements over the siding point, the Ground frame lever is normalised and the key is taken out, inserted in EKT and turned to right. When the key is turned a relay "Siding NPR" picks up at the panel. The signals concerned can be taken off only when the siding NPR is energised as shown in Fig.4.12 Siding can be signalled or non-signalled according to frequency of the shunting operations. The siding controlled from the panel will be invariably provided with signal. If a signal is provided to control the entry into the siding, the movement from the siding shall also be controlled by a signal. Where siding point is not protected by a signal, the responsibility of locking the siding point and holding it for shunting operations rests with the traffic department. 24

* Siding point is provided with Electrical detector and proves normal condition of the siding point. Fig.4.13 SIDING NPR CIRCUIT WITH ELECTRICAL TRANSMISSION OF SIDING CONTROL KEY. 25

4.10

DOUBLE CUTTING OF CIRCUITS:

As per the specification, double cutting also is required for safety. This is achieved by providing controlling contacts on positive and negative side of the relay coil. Circuit without double cutting.

FIG. 4.14 A positive polarity of voltage if connected to relay coil bye-passing the controlling contact it will pick up the relay since negative Polarity is always available with Relay terminal. Circuit with double cutting.

Fig. 4.15 Both polarities should appear on relay to energise it, by-passing all required conditions. Therefore, all outdoor circuits whether vital or non vital should have double cutting in all cases (irrespective of RE and Non RE area.) All indoor vital circuits should also have double cutting for important relay contacts. 4.10.1 Common Return Circuits: Two circuits having same negative path are called circuits having common return. This practice is resorted to; to save conductors and relay contacts. Due to many undesirable features common return circuit are not permitted. Therefore relay should have individual returns and this is possible with negative being cut with controlling relay contacts. 4.11

CONCEPT OF CROSS PROTECTION.

Cross protection is an arrangement by which any vital relay such as HR, WNR, WRR is prevented from picking up, in case a foreign feed appears on relay terminals when the conditions are not favorable for the relay to pick up. This is achieved by shunting the vital relay coils with the contacts of those relays, which are not favorable for the picking up of relay. For example while ASR is in pick up condition, the concerned HR should not pick up. For this HR relay is shunted with ASR front contact. 26

When 1 ASR is picked up if feed appears on the HR coil, then it gets short circuited through 1ASR front contact and HR cannot pickup. Similarly, WNR/WRR should not pick up when WLR is dropped. arrangements for WNR/WRR is: -

The cross protection

Fig. 4.16 This wiring arrangement also ensures the integrity of cross protection loop i.e., if the cross protection loop get disconnected at either end of the cross protection contact, the circuit for the relay also gets disconnected. 4.12

SECTIONAL ROUTE RELEASE (SRR)

SRR is an arrangement by which the route covered by a train is released section by section. This is to free the point/LC behind the train even before the train has completed its journey even before occupying the berthing track. By this arrangement the points which are cleared by the train are made free earlier to increase the flexibility of yard. The effect of SRR will be significant in bigger yards where the distance between signal and berthing track is considerably more. To achieve sectional route release in major yards the route is divided into small sections according to the point zones. Each route section except the first is controlled by relays called TRSR/TLSR. TRSR is applicable for movements from left to right direction, TLSR being effective for right to left direction train movements. The TRSR and TLSR do the same job as ASR except that TRSR/TLSR is responsible for holding the points of the route section ahead through concerned WLRs. The indication and Dead Approach/approach locking are released by ASR circuit itself. However in ASR circuit, all back lock track circuits are not proved. ASR in turn controls TRSR/TLSR according to the direction. For example if TRSR of a Route section is controlled by ASR of home signal then TLSR of the same section will be controlled by ASR of starter signal. TRSR and TLSR together control WLR of the points concerned. 4.12.1 Circuit of TRSR and TLSR: ASR circuit will be modified as follows to be controlled by only the first three track circuits, instead of the entire back lock TPRS. This means that ASR picks up when train clears the first three track circuits, provided indication and DA/approach locking are also proved free. Referring to the layout, Circuits for SRR are given below: -

27

Note:-

Point No. 2&3 WLRs are controlled by for right movement with 1ASR & for left hand movement with 2TLSR. Point No. 5&6 WLRs are controlled by 6TRSR for right side & 12 ASR for left side movements. Fig. 4.17 28

4.13

SIGNAL CONTROL CIRCUITS (HR)

The caution aspect of a signal is controlled by HR. Attention aspect is controlled by HHR and clear aspect is controlled by DR. The ‘ON’ aspect maintained through back contact of HR. Circuit explanation for HR relay is given below: In the given layout, there are three routes for home signal. Again it may be seen that, the loop lines are having two overlaps, one with the overlap point in normal and one with the overlap points in reverse. Therefore, HR can pick in 5 ways. If more lines are available, more paths shall be available for HR to pick up. 1 HR CIRCUIT

Fig. 4.18 4.14

ROUTE RELEASE CIRCUITS: (UYRs)

It is to be understood that the Route locked for a signal movement should get released only after the train has arrived on proper signal in proper direction and the track circuits have been sequentially actuated by the train. This is registered by the picking up of sequential proving relays (UYRs (some railways call them as TPZR, TSSLR etc.). The pick up contact of UYRs are used to energise ASR in the normal route release path. To ensure that the route is getting released only after the sequential occupation of tracks by a train arriving in proper direction, the UYRs are picked up in a pre-determined fashion.

Fig : 4.19 Following is the sequence of train movement and sequential operation of TPRs. 29

1.

When the train is on 1st track only, 1TPRdown, A2TPR up

*Proves train entered on the route one proper signals that is TSR drops. 2. 1 TPR and 2 TPR both occupied and A2TPR up UYR1 pick up and sticks. 3. 1 TPR cleared and both 2 TPR and A2TPR are occupied UYR2 picks up and sticks. With the first sequence, UYR1 picks up and with the second sequence, UYR2 picks up. These above two sequences are possible only with the passage of train and not due to battery failure or track bobbing or power failure. In these circuits the de-energised contact, of two consecutive track circuits TPRS are proved together to pick up UYR. Total 3 track circuits are utilised for proving sequence. In addition to this, it is also a practice to include the back contacts of all track circuits in the route including berthing track in route release circuit, to guard against permanent energisation of any track relay either due to mechanical or electrical problems. Why UYRs are made slow to release? ASR picks up through UYRs front contact. Therefore, it is necessary to ensure that after the train arrival UYRs do not drop unless sufficient time is given for ASR to pick up and stick. Any failure in the time delay arrangement will not give sufficient time for ASR to pick up resulting to a failure and this aspect is to be taken care during maintenance for a trouble free working. Summary of UYRs • • • • • • 4.15

UYRs are normally in de-energised condition. UYRs are picked up to assist ASR to pick up, and it proves that train has successfully traveled over the route by sequentially occupying all the tracks in the route. These relays are named after signal concerned. Front contact used in ASR circuits and also for its stick path. Back contact proved in HR circuit. UYRs are having slow to release feature. ROUTE RELEASE BY TIME DELAY (EMERGENCY CANCELLATION )

While dealing with ASR, it was explained that in case of Dead approach locking, the route will be released only two minutes after the normalisation of signal knob, if the train has not passed the signal. Let us examine how the time delay, is made effective. This is made effective by one of the following means: • • •

Mechanical Time Release Relay operated by a Mechanical timer with reduction gear. Thermal element relay (QJ1) Electronic Timer Relay.

IN MECHANICAL TIME RELEASE, the rotation of a gear system makes the Reverse contact after two minutes. The reverse contact is used in picking up ASR. This is not used now a days. QJ1 is a Q series timer relay, which has a thermal coil and a bimetallic strip. This is used along with another Q series relay called NJPR. The circuit is as follows: 30

Fig. 4.20 A common time element Relay is used for releasing routes of a group of signals or all yard signals. In that case, two more relays are used along with it, viz. RJPR & NJPR. In addition an individual ‘JSLR’ is provided, one for each signal or for a small group of conflicting signals. This, along with the common NJPR, provides for selection of time release in the concerned ASR circuit. While NJPR picks up at the end of JR operation, RJPR is used to prove the dropping of all concerned JSLRs, before a JR operation is initiated i.e., one timer operation for cancellation of one signal at a time. When SM has to cancel the route, he puts back Signal switch to normal. With this HR drops following which HECR etc. drops JSLR picks up through ASR drops. Through JSLR up contact the thermal coil gets feed. Due to the difference in the coefficient of linear expansion of Inver and brass, the bimetallic strip under goes an upward bend and this makes Hot contact. The thermal unit is fed through the back contact of JSR (JSR is the Neutral Relay in the same enclosure). As soon as hot contact is made, JSR picks up and sticks through its own contact. Once JSR picks up, the feed to the thermal coil gets cut off and the strip starts cooling down. After a time lapse, bimetallic strip goes back to original position and a set of contacts called cold contact will be made. (refer S5A for more details). The cold contact and JSR front contact together pick up JR or NJPR, which is a Q series relay connected externally. When JR picks up the ASR energises and releases the route. 4.15.1 ELECTRONIC TIMERS: To get the required time delay, now-a-days electronic timers are used. The electronic timers are having solid state electronic circuits inside. This gives an output, two minutes after the input is given (for details of the working principle of timers please refer S5A Notes on Relays). Since the Electronic circuits using semi conductors are not treated as fully reliable, it is a practice to use two Timers in parallel and their contacts in series for releasing the route as shown below.

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FIG 4.21 4.16

CALLING - ON SIGNAL:

Calling on signals are used now a days very widely to increase the efficiency of signalling system. Calling on signal is an emergency manager in the sense that this is used when the main signal above has failed. C.O signals is taken off even for receiving a train on obstructed lines. Therefore it is useful to deal with traffic during track circuit failure also. In all the latest installations C.O signals are being provided. With C.O signals, the detentions are minimised. The features of Calling On signal are as follows. Ref.GR.3.13 A Calling On signal is a subsidiary signal. It has no aspect in the ON position. It shall be a miniature colour light provided with a `C’ marker. C.O signals can be provided below any stop signal except Last Stop Signal. A Calling-On signal, when taken 'OFF' calls on the Driver of a train to draw ahead with caution, up to the next Stop Signal after the train has been brought to a stop even though the stop signal above it is at ON. C.O signal indicates to the Driver that he should be prepared to stop short of any obstruction. We will also examine the provisions of SEM relevant to CO signal, in addition to the features mentioned above. SEM 7.19.5 (b) The calling on signal shall not be capable of being worked at the same time as the main signal above or shunt signal below it, if any. (c) It is desirable to provide track circuits at a suitable distance in rear and a time delay circuit to ensure that the C.O signal is taken OFF only after the train has been brought to a stop. (d) A C.O signal shall detect all points in the route, which the main signal above detects excluding overlap in double line section. On single line section under approved special instructions a calling on signal placed below the first stop signal may not detect points in the overlap. 32

(e) At stations where SM controls the reception and despatch of trains, such control shall be extended to Calling On signals also. Further it is not required to prove any track circuit in Route and overlap for C.O Signal clearance. However, other conditions related to interlocking shall be the same as that of main signal above it. However, Calling On track should be occupied for the prescribed time for clearing a Calling On signal. This time delay is achieved by timers as mentioned earlier. It is desirable to provide, replacement track circuit for the C.O. Signal to go to ‘ON’ after passage of the train. Referring to the layout under study let us examine how C.O signal below Home Signal No.1 is Controlled. Like a main signal, C.O signal also has a control switch. Route is to be set as usual. CRS approval is obtained for the exempting detection of points in overlap in case of Single line yards. C.O signal will have separate UCR, ASR, JSLR, and HR. Route indicator above is not lit for C.O signals. Track circuit occupation sequence (UYRs) can’t release the route after a train is passed on C.O. Signal. Therefore the route release is always after a time delay of 120 secs. Certain railways use a Calling-On cancellation button on panel for releasing route locked by C.O signal. Again since the route of C.O. Signal is getting released on-conditionally, some railways release the route after 240 seconds. DC lighting for Calling On Signals. Of late, DC 110 V is used to feed C.O signal to make it more reliable i.e. to use Calling On signal to work even when the main power supply has failed. This practice has been adopted in certain railways It is to be understood that, C.O signal is a crisis manager and the system for clearing C.O signal should be such that, the chances for its failure are very less.

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4.17

DISTANT AND INNER DISTANT (SECOND DISTANT):

The provision of one more distant signal is an essential requirement when the breaking distance has got increased due to increase in speed of train. In the sections where Rajdhani /Shatabdi Express are dealt the provision of second distant is mandatory to cope up with the increase in breaking distance for giving pre-warning to drivers. (In Railways the provision of second distant in such sections are in progress) The relevant provisions of GR regarding second distant are as follow, Ref.3.07. (6). "Where necessary more than one distant signal may be provided. In such a case the outermost signal to be located at an adequate distance from the first stop signal, shall be called the distant signal and the other called inner distant signal, with the distant signal capable of displaying attention or proceed aspect only". Accordingly, distant signal will have only two aspect and the normal aspect being attention (Double yellow). The inner distant will have three aspects viz. caution, attention and clear. The distant signal assumes clear for the reception on main line only. For all other cases, it displays attention aspect only. The inner distant signal however assume clear aspect only for run through. Except for this, the aspects of inner distant will be as in the case of normal distant signal. The sequence and circuit for aspect control for distant signals will be: -

Fig.4.23 4.18.1 INDICATION CIRCUITS: Indications are given on the panel for the guidance of operator and maintenance staff. Following are the indications for the various functions. Indications are of two types: - Strip light type and spot light type. Signals: Indication is given aspect- wise and route- wise through concerned ECR front contacts. Colour of indications, corresponds to the colour of aspects. When ever ECR is not used, indication transformer is used for indications. Circuits are as following: Fig 4.24

34

35

36

Fig 4.27 Track occupied indications are given through the back contact of TPR. This should appear at all times whenever a track is occupied, irrespective of route set or not. Two lamps are given to overcome the problems due to bulb failure. If one bulb fails at least other will maintain the indication. “Track circuit occupied” indication is very important for safety point of view. In addition to this, following indications are also given on the panel. Route locked indication. This will be “white” when the route is locked (ASR) and when no train has occupied the route and ‘Red’ when occupied. With the release of Route, this indication also disappears.

Fig. 4.28 4.18.1.1 Route locked indications : (Strip light type) are given through ASR back contact, since ASR dropped condition ensures route locking. The route locked indication is given from the foot of the signal to the next signal on the route already set excluding overlap. 4.18.1.2 Point Indication : Point indications are given through NWKR/RWKR front contact. Conventionally ‘white’ colour is used for normal and ‘green’ for reverse position. Point free indication can be given through WLR contacts.

37

4.18.1.3 Flashing Indications : Flashing indications are also given to indicate that the point is under operation or point indication has failed. Flashing supply is derived from a mercury pendulum flasher unit. Recently railways have gone for electronic flashers. 4.18.1.4 Power supply arrangement for indication Circuits : 12V DC or AC can be used for indications supply. 12V, 1.2W pencil type lamps are used. The DC is preferred to AC because of its stability and consequent increase in life of lamps. The power supply failure also do not affect indication if DC is used. If AC supply is used, it is desirable to make it stabilised and uninterrupted. Recently LEDs are used to give indication to avail the benefits of long life and very less power drain. At 12V, 1.2W rated bulb consumes 100ma whereas LED drain will be around 2 to 5 ma only. However special attention are to be laid for managing with the problem of poor visibility due to the interface of external light. 4.18.2 SIGNAL LAMP FAILURE ALARM CIRCUIT : This circuit is employed to give an audible and visual indication to the operator whenever any of the signal becomes blank due to Signal lamp fusing. The Circuit is given below. The functioning of the circuit is explained below :Relay GXJR picks up through any one of the ECR pick up contact of all the signals proved in Series. Hence this relay is normally energised relay. This relay is made slow to release to cater for the prevention of relay dropping due to aspect changing. If any signal becomes blank, the feed to GXJR Relay is cut and relay drops. Through the de-energised contact of this relay, the alarm rings, which will continue to ring till such time the ACK. Button is pressed and GXYNR Relay is energised. The visual indication also will appear as soon as GXJR is de-energised. This indication remains till such time the fused bulb is replaced by a good one and GXJR is energised.

FIG 4.30

38

4.18.3 POINT FAILURE ALARM AND INDICATION CIRCUIT : The functioning of this circuit is similar to the signal Lamp Failure Alarm Circuit explained earlier, except that the NWKR/RWKR energised contacts are proved in GXJR circuit, instead of ECR energised contacts. The circuit is as following : -

4.19

INTERLOCKING OF LEVEL CROSSING GATE :

4.19.1 Method – I : In this method, the level crossing annuciator relay (LCAR) is kept normally energised in the gate lodge when no route over the level crossing has been set. As soon as any route is set, the concerned ASR/TRSR/TLSR drops which in turn de-energises LCAR. This causes the road signal on either side of the level crossing to display red aspect and the bells also start ringing. The Gate-man closes the gate and locks it, by taking out the key. The key is inserted in the ‘E’ type lock provided in the gate lever (GF) and turned for unlocking the lever. The lever is then reversed. Through the reverse contact of the gate lever, the LCPR relay picks up in the relay room, which in turn causes the HR of the concerned signal to pick up as the front contact of LCPR is proved in the HR circuits, thus permitting the signal to be taken OFF. After the movement is completed, the route is released. ASR/TRSR/TLSR picks up. LCAR picks up in the lodge and give ‘Free indication. The lever lock is energised permitting the gate lever to be normalised. The key is taken out from the lever and the gate is opened.

Fig. 4.32 39

4.19.2 METHOD – II . In this method, the Gate-man is instructed on phone to close the gate whenever any movement over the gate is to take place. The Gate-man closes the gate and transmits the key from the EKT. The Station Master takes out the key from the EKT connected to the gate and inserts the key in the LC-EKT and turns. LXPR relay picks up and sticks provided the gate knob is normal. Energisation of LXPR permits the HR to pickup and the signal is taken OFF. After the movement is completed, the route is released. ASR/TRSR/TLSR picks up. The gate knob is reversed for releasing the key. Gate RR picks up. The key is extracted by pressing the push button and then transmitted through the other EKT. The Gate-man takes out the key from his EKT and opens the gate. LXPR relay is de-energised as the key is taken out and locks the concerned signals. The above arrangement can be used for L.Cs which are not busy. provided, Method I can be adopted.

If road signals are to

Fig. 4.33 4.20

VOLTAGE DETECTING CIRCUIT :

As all relays in the cabin, track relays etc., are fed by DC voltages derived by transforming and rectifying AC supply, any fluctuation in the AC voltage will result in the random dropping away or picking up of relays. Suppose a route has been set and signal cleared and at that time a very quick momentary voltage fluctuation occurs; Track relay used in TSSLR & TSR relays may drop and pick up. Now if the signal knob is restored to normal the route may get released instantaneously without any time delay. To eliminate such a contingency the front contact of R relay in voltage protecting circuit is used in the ASR; TSSLR and time element circuit.

40

The circuit diagram for the voltage detecting circuit is given below:

Fig. 4.34 Normally relays LVR and R are kept energised. LVR is directly connected across the supply. A resistance connected in series brings down the holding current of relay LVR to a value closer to its drop away value to make it more sensitive to voltage fluctuations. R relay normally remains picked up through LVR front contact. When AC voltage goes below a certain pre-determined value, LVR drops and consequently relay R drops. Bell circuit is completed through LVR (B) – R (B) – LPR (B). This circuit is connected to battery so that the bell rings even when supply fails. SM presses power acknowledgement button ‘P’ ack., LPR relay picks up and sticks. Bell is stopped. When voltage comes back to normal, LVR picks up. (Shunting of series resistance by R back contact permits LVR to operate). SLR slowly picks up through back contact of R proving that the power supply is stable. Meanwhile operation of LVR disturbs the LPR stick circuit and LPR drops, connecting the bell in circuit. SM acknowledges the restoration of power by pressing ‘PAck’ button .LPR relay picks up and holds through LVR front and R relay back contacts, cutting off the bell once again. Simultaneously R relay picks up through SLR front contact and sticks. The back contact of R relay cuts off SLR, LPR & bell circuits. Circuit is now normal with R and LVR in energised condition.. EXERCISE:

1.

Prepare Block Diagram for the sequence of relay operation for a) Point operation. (b) Route release (c) Emergency route

cancellation. 2. Write short notes on UCR, ASR, WLR, UYR, NJPR 3. Prepare 10UCR, 3/5/7ASR, 10HR,Co 10HR, and shunt 12 HR.

41

CHAPTER – 5

S5J1

RELAY INTER LOCKING NON ROUTE SET METHOD (BRITISH) PANEL INTERLOCKING (CONVENTIONAL TYPE). 5.1

Introduction :

In the early days, the points and signals were operated mechanically by means of levers located in an interlocked lever frame. The mechanical lever frame could control a limited area. This limitation made it necessary to provide number of signal cabins in a large yard and the signalling of trains through such areas were difficult due to the need for close co-operation between the cabinman, when operating their respective signalling gears. The invention of electrical equipments for operating points and signals and the subsequent invention of power frame, marked a big advancement in signalling practice. Number of signal cabins were replaced by one power cabin by the use of power frame. The miniature levers of the power frame, with their negligible loading and closer spacing allowed a much greater areas to be controlled by one signal man. The interlocking provided in the power frames were either mechanical or electrical. The improved working afforded by the power frame promoted serious thoughts in the minds of signal engineers, on the subject of further increasing the advantages already gained. In due course this resulted in the developments of small control panels with miniature switches and interlocking between points and signals being achieved through relays, which is called as “Relay Interlocking”. 5.2

INDIVIDUAL SWITCH PANEL SYSTEM:

The panel used in this system is co called because each signal and points have an individual switch for their operation. There is no physical interlocking between panel switches and they are consequently free to be moved to any position, but the associated interlocking relays will not respond until their releasing circuits are established. This type of relay interlocking between individual functions (points and signals) operated from “individual system is used for controlling small stations involving less number of points and signals. The panel resembles in illuminated diagram on which a geographical reproduction of the layout is depicted and the track circuits are indicated in the usual manner. The aspects of signals are repeated on the panel in positions corresponding to their actual location at site. The control switches are located below the layout. Each points is provided with a two position points switch which can be operated either to ‘N’ position or ‘R’ position according to the position of the point required. In a small station with two roads the reception signal and opposing departure signals cannot be taken ‘OFF’ simultaneously. As such, instead of providing three 2 position signal switches (one for each signal) only one 3 position signals switch is provides. Normally the switch remains in centre position. Whenever signals leading to left ward movement is to be taken off, the switch is turned to left (‘KL’ position) and whenever signals leading to rightward movement is to be select off the same switch is turned to right (‘R’ position ). After the passage of the train the switch is replaced to centre. By adopting this method the number of switches required on the paired is minimized (Ref .Fig 5.1).

42

Fig :5. 1 The above arrangement is adopted in case of single line layouts only. In case of double line layouts, each signal will be provided with one knob to cater for parallel movement of trains. In recent installations irrespective of single Line or double line separate knob for each signal is provided. In this system for clearing a signal all the point switches must be operated to the required position one by one and finally the signals switch is operated. The signal may pertain to more than one route. According to the setting of points, the signal will clear for that particular route. After the operation of the signal switch operation of conflicting signal switches of point switches will not have any effect as it is protected by the Relay Interlocking circuits. 5.3

CIRCUIT EXPLANTION :

For the purpose of understanding the circuit can be classified as under:1. Point Control and point setting circuit. 2. Point indication circuit. 3. Signal lock relay circuit. 4. Route Checking Circuit. 5. Approach & Route locking circuit. 6. Track stick relay circuit. 7. Signal control relay circuit. 8. Signal aspect control circuit. 9. Track stick slow release relay circuit . 10. Panel indication Circuit. For the explanation of circuitry signal No.1 in layout given below (Fig5:2) is considered. For clearing the signal to road 2 points 101,102,103 and 104 are operated to the required positions by operating the respective point switches to the required positions.

43

5.3.1

Point Control and Point Setting Circuit.

The point is controlled by a point lock relay (WLR) which is kept in the cabin and point controller (WNR/WRR) kept near the point machine. WLR is a neutral relay and WNR/WRR is are the point control. Relay for normal and Reverse operation of point respectively. The points can be operated, when the following conditions are satisfied. 1. 2. 3.

SM’s key should be in the panel to ensure authorised operation (Fig. No.S5J 2.3.1(a). Point track relay should be energised to prove track locking is freed and Approach stick relays and sectional release route lock relays (TRSRs/TLSRs) are energised to prove that the point have not been locked for any other route.

Approach stick relays are generally provided one for each signal to achieve approach locking , back locking and indication locking. Where sectional release route locking is provided. Track Right stick relays (TRSR) for right ward movement and track left stick relays (TLSR) for leftward movement are used. These relays are normally kept energised. When a signal knob is turned for clearing a signal, the picking up of UCR causes ASR to drop and this in turn causes TRSRs/TLSRs to drop. The back contacts of these relays are used in HR circuit to prove that the points are locked in a route, before a signal is cleared. Note : Generally t wayside stations where panel interlocking is provided, sectional route release locking is not catered for. Point operation switch is a two position switch. This can be operated either to ’N’ position or ‘R’ position depending upon the requirement. This has 2N/R contacts. For clearing the signal No.1 to a Road 1 with overlap set to sand hump, switches 102 and 103 are operated to Normal and switch 101 is operated to reverse. When WNR picks up, the point is operated to normal and when WRR picks up the point is operated to reverse 102 and 103 operate to normal through their respective WNR and point 101 operate to reverse through 101 WRR. Note : Some Railways Adopt the method of keeping WLR de-energised normally (by including de-energised contact of NWKR/RWKR in WLR circuit) with an advantage of avoiding drainage of power supply continuously.

44

5.3.2

Fig :5.3 Point Indication (detection) Circuit :

This circuit employs two neutral relays one for proving the points are normal and the other for reverse. When points are set and locked in Normal. Relay NWKR picks and when points are set and locked in reverse relay RWKR picks up. The contact of WNR/WRR is not included in the detection circuits as these relays de-energise, when signal is cleared.

Fig :5.4 5.3.3

Signal Lock Relay Circuits :

As explained earlier, the home and the opposing starters, are controlled by a 3 position humb switch. The switch normally remains in the centre position. This can be turned to right or left depending upon whether it is a rightward or leftward movement. For clearing Home Signal 1 to Road 1 or 2 the switch ‘1’ has to be turned to right and for clearing opposing starters. It has to be turned to left. For clearing Home Signal 5, switch ‘5’ has to be turned to left and clearing opposing starters it has to be turned to right. Each 3 position switch is provided with two relays. When the knob is turned to clear a despatch signal “SR” (sending or starting relay picks up and when the same knob is turned to clear a reception signal ‘RR’ (Reception or Receiving Relay) picks up. The back contact of one relay is used in the circuit of the other to ensure that both do not energise at a time. In some circuits the centre position of the knob is proved by a third relay ‘NR’. This is not used in these circuit, as these circuits are wired with metal to carbon relay contacts. For energising the SR/RR relays, the following conditions are to be satisfied . 1. Knob is to be turned to left or right 2. SM’s key should be ‘N’ 3. The back contact of the SR should be available for energising RR and vice versa. Once these relays pick up, they do not drop even if SM’s key is taken out. This is achieved by bridging (I) the SMR front contact by NR/RR front contact and (II) ‘L’/R contact of the thumb switch by SMR back contact, to ensure that these relays do not drop when the panel is locked by SM and the signal switch is turned back to Normal by unauthorised persons.

45

The circuit for 1 SR,1RR ,1RLR and 1SLR are given here under :

In the above circuit 1RR energised contacts in 1RLR circuit proves that the signal knob is turned to right for reception of a train. De-energised contact of 1SLR, 3LR, 2LR, 9LR and 10RLR are proved since they are conflicting signals. 9LR and 10RLR are bridged by 4RWKR front contact and 7 RWKR front contact in series to facilitate simultaneous movements. Similarly bridging of these contacts by 5RWKR front contact and 6 RWKR front contact is for simultaneous movements. In recent installations, separate switches are provided for Home and opposite starter signals as shown in the layout given at Fig.2. In such case, there will not be SR and RR. Concerned signal lock relays or route initiation relays (LR/RRs) will pickup proving the conflicting signal LR/RR dropped. The level crossing and siding points also will have controlling knobs. The circuit for 1LR is as under.

Fig : 5.6 The basic requirements for picking up of LR relay is the de-energisation of conflicting LRs. This can also be achieved by proving concerned point detection relays (NWKR/.RWKRs) in the LR circuits, if it is economical (amounts to reduction in no.of contacts.) 5.3.4

Route Checking Circuit:

The function of this circuit is to check that the route is correctly set before the signal is cleared. Each signal is provided with a route checking relay (UCR).

46

The picking up of UCR initiates the route locking circuits, and enables the route locking condition being proved in the HRR circuit.

Fig : 5.7 Note : It is a practice in some Railways to prove the conflicting signal ASR in UCR circuit. Concerned CHLR is also proved in some Railways. 5.3.5

Approach & Route Locking Circuit:

Generally each signal is provided with an Approach Stick Relay (ASR) to achieve the approach locking, back locking and indication locking. Whenever UCR picks up it results in ASR dropping. When ASRs de-energise, they cause point lock relays (WLRs) to de-energise thereby locking the points in the route. When 1UCR picks up it makes 1ASR to drop. 1 ASR dropping causes 3 TRSR to drop. Dropping of 1ASR de-energises 2WLR and dropping of 3 TRSR de-energises 3WLR & 4WLR, thereby locking all the three points in the route. Two or more signals can be provided with common ASR as shown in P-56, when then route is same and these signals are conflicting.

Fig 5.8 47

5.3.6

Track Stick Relay Circuit.

This is a conventional SR circuit used to ensure that “One Train on One Signal”. This relay (TSR) is normally energised through the front contact of controlling track & back contact of the RLR & SLR. Once this relay pick up, it gets a stick feed bypassing RLR & SLR back contacts. When a signal is cleared RLR/SLR picks up. Even then TSR remains picked up through its own contact. When the train passes the signal and occupies the controlling track. TSR drops. When the train clears controlling track, TSR cannot pick up till such time the signal switch is replaced to Normal causing RLR/SLR to de-energise. TSR (F) is used in HR circuit. This arrangement ensures that after the passage of the train, the signal cannot re-clear automatically unless the signal switch is replaced to normal and operated once again. In latest installations , ASR contact is also proved along with LR back contact in TSR circuit to prove that the previous train cleared the route.

Fig : 5.9 5.3.7

Signal Controlling Relay Circuit (Fig.

Each signal is controlled by a HR relay. For clearing a signal, the following conditions are to be satisfied. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

The line should be clear up to the next signal in advance and adequate distance beyond it (TR front contact). All the points in the route are correctly set and locked including the overlap (NWKR/RWKR). Route is checked and Signal knob is operated to the correct position (UCR). Points are electrically locked (WLR ). Points are locked in the route (TRSR / TLSR) Signal is approach and back locked ASR ). Only one train can be admitted on one signal (TSR ). Time release associated with signal is in operation (Mechanical Time release normal contact). Opposing signals are not cleared (Opposing signal ASR). Route lamps are lit before signal is taken off for turnout (UECR). Block Control is available for last stop signal. Signal ahead aspect is available (GECR front contact) when all the above conditions are satisfied HR picks up.

48

5.3.8

Signal Lamp circuit.

This is the conventional multi-unit colour light signal circuit with cutting in arrangement.

5.3.9

Sequential Route Release Relays (UYRs)

These relays are provided to release the approach track locking of signal when a train has passed the signal, independent of whether the approach track is occupied or not. These relays are made slow to release as the front contact of this relays used to energise ASR Relay and the back contact of ASR is proved to energise TSSLR/UYRs. Now a days, the practice is to prove more than one track relays for this purpose to avoid release of route during track circuit bobbing conditions. The pick up and drop contacts of all the back lock track circuits will be used in the circuit as shown in Fig .

49

5.3.10

Panel Indication Circuits (Fig.)

When route is not set, no indication is given on the panel. When a signal is cleared and points are locked in a route a row of white lights light up the whole length of the route. These lights are given through the back contact of ASR TRSR/TLSR and the relevant track front contact. When the train occupies the lights turn to Red through the TR back contact irrespective of whether the route is set or not. The point indications are given through point indication relay front contact and signal indications through lamp proving relay, front contacts.

50

Fig : 5.12

CHAPTER – 6

S5J1

RELAY INTER LOCKING ROUTE SET METHOD BRISITSH RRI SYSTEM – II 6.1

INTRODUCTION

51

With difference in point control circuit one more system called System -II RRI has been evolved for easiness in design of the circuitry. What ever has been discussed earlier is coming under System - I and System -II is explained hereunder:System -II is adopted for major yards where no. of parallel moves and shunt signal movements are involved. The point control circuits are prepared in geographical manner. All other circuits are same as system - I. Instead of many LRs in point control circuits only 3 relays i.e., ANR, BNR and RR only will be used in System - II. ANR or BNR controls the operation of point to normal and RR will control operation of points to reverse. Following circuits for point no.101 for the layout under study will illustrate the need of system - II method of control of point operation. The ends of cross over points are designated as A end and B end. Single end points will have no special designation. To appreciate the utility of this system, let us consider the yard given in figure 1. We may assume that all signals read to all possible roads. Thus we have 4 routes for each signal, and a total of 8 x 4 i.e., 32 routes. Considering points 7, we have 24 routes requiring the points in normal position and 8 routes in reverse. The point control circuit (WNR/WRR) become too involved with the large number of LR contacts. Also the number of route lock relays required is prohibitive. Therefore, the system No. 1 so far used is suitable only for small stations and not for big yards with more shunting movements.

Fig No :6. 1 To illustrate the principle employed in this system, let us consider the layout given in Fig.2. The route selection circuit is drawn in a geographical manner, i.e., the circuit when drawn will resemble the track layout closely.

The ends of cross over points are designated as A end and B end Single ended points will have no alphabet to specially designate the end, as there is only one end. For example in the yard at Figure above the ends of cross over points 11 are called '11 A' and '11 B' and the end of points 12 is '12'. Each end of points is associated with 2 relays for the normal setting of points, one of them is designated as 'CR' and the other NR. CR is picked up when points are free i.e., not used by any other route requiring these points in normal position and NR is picked up after ensuring that the complete route is free. There is also a reverse relay RR associated with each points. Only one RR is used irrespective of whether the points are double ended or single ended. RR relay is also energised only after checking the availability of the entire route like NR 52

relay and sets the points reverse when energised. Thus we have 5 relays for a cross over ANR, ACR, BNR, BCR & RR (e.g., for 11 points 11 ANR, 11 ACR, 11 BNR, 11 BCR & 11 RR). Any one of the NR relays either ANR or BNR will set the points normal. All the five relays are required for a crossover only when we have movements on both ends with points normal and with points reverse. In case of a cross over with one end having a sand hump only, 3 relays are required, NR and CR for the end having no sand hump and RR for reverse setting of points. For single ended points like points 12 in Fig. 2, only 3 relays are required NR and CR for the end having no sand hump and RR for reverse setting of points. The route selection circuits are drawn in two parts. The circuit for any signal commences from the entrance end of the route, advances geographically in the direction of movement of train to the exit end. The circuit then folds back through the second part and terminates at the entrance point of the route. The forward flow circuit starts from the signal with switch reversed contact. While progressing ahead, the availability of the route is ' checked. When a trialling point is encountered in the normal position, in addition to proving that points are not used by a route requiring these points in reverse position, a relay known as CR (Checking Relay) is energised. This CR relay prevents any other conflicting route being initiated. When a CR relay energises, a circuit for the operation of the associated NR relay is also prepared in parallel but this relay will operate only after proving the entire route is free. When facing points are encountered in the forward flow circuit is merely proved that the points are not used for reverse. No checking relay is picked up in this forward flow circuit, but these points will have their CR & NR relays picked up in the return direction. When the route involves points in reverse position, circuit for RR is either prepared in the forward flow circuit and operated after ensuring the entire route is free or prepared and operated in the return circuit. Therefore, the RR relay for any points will whether be located in the forward or return circuit. Thus the forward flow circuit extends proving the availability of route to the exit end where it proves the opposing signal knob (if any) normal and energises push button relay through the exit push button operated contacts. When the push button relay operates, the circuit folds back and extends towards the entrance end. The conditions proved are exactly similar to the forward flow circuit. As stated already the trailing points in the return direction have their CR and NR operated. Where the route is through reverse setting of points, RR relays of relevant points are energised. The operation of point control relays NR & RR is done sequentially in the return direction irrespective of whether they are facing or trailing. The first point NR or RR in return direction is controlled by the push button relay. The second point NR or RR is energised by the first point NR or RR relay, the third point NR or RR by the second point relays and so on. Thus an NR or RR relay is energised by the NR and/or RR contacts of the points on either side; or push button contacts in the absence of points. For example in figure 5, 11 BNR is controlled by APR for one side and 13ANR and 13RR is controlled by 11 BNR and DPR. Contact of 11 RR is not used as it is assumed that no movement with 11 reverse is permitted with 13 points in reverse position. Finally, for points to be set in normal, NR and CR relays of the ends on which the rout extends and for points to set in reverse RR relays operate. These relays control the point controller circuits (WLR/WR) for setting the points in the required direction.

53

The detailed circuits for route 1D figures 3(a) and 3(b) are now discussed. The forward flow circuit starts with IR contact (knob 1 turned towards right). APR back contact is proved to ensure that no opposite Movement is already initiated. As the points 11 are approached in trailing direction and they are required in normal position, 11 RR is proved de-energised. This ensures that no route requiring 11 reverse is already set. With these conditions the checking relay for B end 11 BCR is picked up which prepares the circuit for 11 BNR - Relay 11 BNR will pick up only after proving the entire route is free. If this relay were allowed to operate immediately after 11 BCR has picked up, 11 points would unnecessarily operate even when full route is not available. With 11 BCR operated the circuit extends further. The next points 13 are approached in facing direction, but they are required in reverse position. Normal position checking relays and control relays of both ends (13ACR, 13BCR, 13ANR & 13BNR) are, therefore, proved de-energised. To ensure that this path of the circuit is available only for movement with 11 points normal and not with 11 reverse, 11 BCR front contact is included. As there are no further points and the exit end is reached, the push button relay DPR is energised proving the opposing signal knob is normal and the push button D pressed. These contacts are shunted by a stick contact of DPR to hold the relay after the release of push button and also to prevent a disturbance to this circuit by subsequent mal operation of knob 4. The return circuit fig. 3(b) commences with DPR front contact and advances towards the entrance end proving 13 points are not used in normal position (13 BCR, 13BNR, 13ANR & 13ACR all de-energised) to pick up 13 RR- Even though these contacts are already proved in the forward circuit and appear redundant, they are repeated to combine the route selection circuits of other signals also with this circuit. DPR contact in 13RR circuit proves that full route is already checked in the forward flow circuit. The next points NR circuit (11 BNR) has already been prepared in the forward flow circuit. Therefore, a front contact of 13 RR is used to energise 11 BNR. The return circuit terminates at this stage as there are no more trailing points or points required in reverse position. 13RR and 11 BNR relays operate 13 points to reverse and 11 to normal respectively. The Point control circuits are similar to those in system-I except that the route lock relay contact (LR) are replaced by NR and RR relay contacts. Cross-over points are controlled by either ANR or BNR for normal setting. As only one NR is used for single ended point its contact will set the points to normal. RR relay will, however, set the points to reverse in either case. We will now consider the circuits of 4A route, the route directly opposite to 1D. The forward flow circuit of 4A route (Fig.4a) starts with 4 knob in the left position. The circuit proves DPR in de-energised position to ensure that no opposite movement to 4AT is initiated. As 13 points are required in reverse position, 13 BCR, 13 BNR, 13ANR, 13ACR are proved de-energised. Circuit for 13 RR is also prepared simultaneously but 13 RR will operate only after proving that the entire route is free. The circuit also proves the back contact of 11 RR (11 points not used in reverse position) and energises APR through opposing signal knob normal contact and exit 54

button ‘A’ pressed. It may be noted that no CR for 11 points is picked up in this circuit as these points are approached in facing direction.

When APR picks up, the return flow circuit is initiated (Fig4b) and 11 BCR picks up proving 11 is not used in reverse position. 11BCR operates 11 BNR as the entire route is already proved to be free, through APR. 11 BN-R operates 13RR.

Fig No :6. 5 Figs. 3(a) and 4(b) are having identical conditions to prove they can be combined to form a single circuit as shown in figure 5, Fig.3(b) and Fig.4(a) are similarly combined as shown in Fig.6.

Figs. 7(a) and (b) represent the forward and return flow circuits for route 2D. As no points are required in reverse position, no Rr relay is energised in these circuits. In other respects, the circuits are similar to those of route ID . Figure 8(a) and 8(b) are the circuits for route 48. The circuits for route 2D and its directly opposite route 4B are combined and given in figures 9(a) and 9(b).

55

56

Fig No.6.10b

57

Fig No :6. 11 58

To illustrate the principle of grouping the circuits of different routes the combined circuits of all the 4 routes discussed above is shown in figures 10(a) and 10(b). Thus the route selection circuits of the entire yard can be combined to form one forward flow circuit and one return flow circuit, to achieve the necessary interlocking using the least number of relay contacts. The circuits are also easy to design. The UCR and HR circuits are also generally drawn in the geographical manner for economy. The layout given at Fig.2 has shunt signals only and hence, setting and holding of overlap points is not required. But in practice, these two (setting of overlap points and holding them) play key role. Let us consider the above yard, it is necessary to achieve locking between signals, set and hold the overlap points. The requirement of overlap differs for main, shunt and calling on signals. Lets us know about the necessity and function of relays associated with point circuits in the system-II 6.2 Checking Relay (CR): It checks whether the complete route is free or not. It also checks whether trailing points in forward flow and return flow circuit are free and normal. These are the following conditions under which this CR relay is energised. It picks up when a route is initiated proving :a) b)

Points are in normal position i.e., R.R down. For trailing points CR picks up during forward flow. For facing points CR picks up during reverse flow (for A end ACR, B end BCR and so on.)

The function of this relay is to select the Straight route when it is energised and Diverging route when it is not energised or to prove that the point is not used in reverse position. This relay is energised either in the forward flow or in return flow depending up on the position of the point in the route initiated. This relay prevents conflicting route initiation (by using back contact of CR in conflicting route relay circuit in the forward flow ). This relay proves that points are free and not used by any route (by picking up of route relay UR concerned) This relay prepares the circuit for normal relay (NR) This relay proves that points are not used in reverse (by proving reverse relay back contacts i.e, RR ) 6.3

Normal Relay (NR): (for setting the point to normal.)

This relay picks-up when : (i) (ii) (iii) (iv)

concerned checking relay (CR) is energised. Route button relay picked up or Adjacent point normal relay or reverse relay is energised for successive operation.. Concerned reverse relay (RR) back contact to prove this point is not used in reverse by any other route.

NR picks up only after CR is energised & controls WNR relay. 59

6.4

Reverse Relay (RR): ( for setting the point to reverse.)

This relay picks-up when: i) ii) iii)

The route button relay is energised. Concerned NR & CR back contacts. This relay picks up in succession by the a) Route button relay or b) Adjacent point normal relay (NR) or c) Adjacent point reverse relay (RR)

Only one RR is used irrespective of Double end or single end points. 6.5 Route Button Relays UR: All the berthing tracks are provided with route button which is also called exit button. When this is pressed, proving other conditions a relay picks up called UR. For Right side movement RUR and for left side movement LUR, followed by the Route alphabet. For example ARUR/ALUR- A stands for the A route button, 'R' for right, V for left, U for route and R for relay. The route relay contacts if used in the flow circuit, if back contacts are used it is for conflicting route, if pick up contacts are used it is to start the return flow circuit. When this route relay (UR) energises, it completes the circuit for N-R or RR for the first point in the return circuit. 6.6 Special Relay ZR: To differentiate and to achieve the locking between main signal, calling on signal and shunt signal there is a special relay introduced called ZR. For each signal route initiating circuit one ZR is used. They are:R/L ZR. for main signal R/L COZR for calling on Signal R/L SHZR for shunt signal

- R for Right - L for Left - M for Mn. signal - Co-Calling on - SH Shunt Signal

6.7 OVERLAP RELAYS: In system II separate overlap setting relays are to be provided for all home signal route, as the route initiation circuit is common for home and shunt signal. Once Route Relay UR picks up, it operates the overlap setting relays. In overlap setting relays also, left, right movements and main signal shunt signal movement can be separately provided to differentiate between main signal,, shunt signal and calling on signal and for overlap setting & locking. These overlap relays are called as OCRs. ROCR & LOCR Right, left overlap checking relay for main signal. ROCR -c& LOCR-c Right & left overlap checking relays for calling on signal. R SHOCR & LSHOCR Right & Left overlap checking relays for shunt signal. OCR controls WLR/WNR if the overlap point is required normal. OCR controls WLR/WRR if the overlap point is required in reverse condition. If there is alternate overlap OCR1 Controls WLR/WNR, OCR2 controls WLR/WRR.

60

The conditions to pickup OCR relay are 1. 2. 3. 4.

Concerned signal knob is operated. LR up Concerned route relay is energised UR up The ANR or BNR or RR relay of all the points required to be operated either to normal or to reverse in the that particular signal route are energised that means OCR before picking up ensures points in the route are set. When required conflicting route relay back contacts are proved in OCR circuit.

6.8 Successive Operation of Points: In system II all the points in the route are not switched on at a time. They are made- to switch on in succession. First the NR/RR of last point in the route picks up then the next point NR/RR will pick up and so on. As soon as NR/RR picks up, the point starts operating. The staggering in the picking up of NR/RR as explained above, makes the staggering also for point operation of switching also. This will reduce the instant heavy battery drain, if all the points start operation at a time (This is equivalent to chain group of Siemen’s System.) i) ii)

First point in Return flow circuit either NR or RR is controlled by Route button relay or (UR). Second point NR/RR is controlled by NR/RR of the first point, then third point NR/RR is controlled by the second point NR/RR and continues so till the first point NR/RR in the forward flow circuit is picked up. Push button relay contact is used in absence of point ahead.

6.9 Overlap holding relays OHR : Every route will have a overlap holding relay depending upon direction of the movement. For example if A route train moves to the left side ALOHR. If it is right side - AR0HR. This relay proves that points are not held by the concerned overlap for the route set. 'This relay picks up when a) concerned route is not locked. i.e,. ASR is up. b) last route section in the route is not locked i.e,. last TRSR up or MR up of the route. c) It is held through its own stick by-passing the last route section lock relay contacts. The pick up contacts are used in conflicting UCR circuit where required and in point control circuit WLR and front contact in conflicting HR & back contact for same route HR circuit. The model circuits for the yard given at Fig. 12 are given hereunder :The first relay to pickup after the route initiation i.e., pressing the route button and turning the signal knob is Route Initiating Relay(LR)

Fig No :6. 12 The picking-up of LR picks-up ERZR proving normal position of conflicting signal and initiates the ‘Forward flow’ circuit and picks-up the route relay for which the route button is pressed say ERUR, through front contact of ERZR

61

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After ERUR picking-up, EROCR (over-lap checking relay of E route right-ward movement) picks-up. The ANR/BNR of concerned point sets the point to normal and RR sets the point to Reverse according to the relay picked-up. The EROCR sets the points in the over-lap to required position.

Over-lap holding relay (OHR): The over-lap holding relay picks-up through the concerned signal ASR pick-up contact and the last directional relay in the route of the signal i.e., 106 TRSR and holds through its own contact by-passing 106 TRSR.

Fig No :6.17 This OHR pick-up contact is proved in all the point WLR circuits in the over-lap of signal No.1A i.e., points No. 110,112W110R,114,115W 110R, 116W110R thereby locking these points in case signal No. 1A is taken off to route E The ASR , TSR circuits are the same as in system 1

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The UCR and HR circuits may be drawn in geograpical manner for economising the contacts. The following circuits illustrates this method.

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