Notes on Solid state interlocking

CAMTECH/S/2002/SSI/1.0

1

SOLID STATE INTERLOCKING 1. Introduction Indian Railways with a network of approximate 62,000 route KM, have approximately 130 RRI (Route Relay Interlocking) and 1450 PI (Panel Interlocking) Installation. These systems requires considerable time in installation, require considerable space and a large no. of relays which makes the system considerable complicated. With the advancement of computer and communication technology it has become possible to incorporate the logic in Electronic Interlocking System which is more compact and easy to adopt frequent changes. Various railways are slowly adopting different types of Electronic Interlocking Systems (SSI) all over the world. Indian railways also have installed Electronic Interlocking System at more than 12 stations including 3 stations developed indigenously. Electronic Interlocking System with object controller has additional advantage of reduced signalling cable requirement with higher overall availability. Various Zonal Railways have already taken up replacement work of existing interlocking system with Electronic Interlocking System.

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2. GENERAL REQUIREMENT i) SSI system provides all the interlocking, control and indication functions as per approved interlocking plan, selection table and Panel/RRI diagram of the station. ii) System comply with the specification No. RDSO/SPN/148/98 for safety and reliability requirement of electronic equipment with the following options: a) b) c)

On line data logging facility Equipment is meant for indoor use Operating voltage as per specification

iii)

System is capable for working in non airconditioned environment, temp. Range between 0° C to 55° C and relative humidity up to 95% at 40° C.

iv)

System is having user friendly graphic based design.

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3. ADVANTAGE OVER RELAY INTERLOCKING 

Approx. 60% reduction in relay used.



50% reduction in space required.



Initial commissioning and changes due to yard remodelling can be carried out in negligible time i.e. less manpower for traffic management during blocks as well as less detention to trains.



30% reduction in power consumption.



Reduction in wiring and interconnections.



Same equipment is suitable for AC electrified area.



No relays are required for interlocking function. Only interface relays are required.



No air –conditioning is required.



SSI has got self-diagnostic features. Any failure in the system is located and enunciated. Faulty module can be immediately replaced by spare module hence the down time of installation is reduced.



Reduction in no. of fuses

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4



Less prone to short cut method, total system goes to shut down if point/ signal is even wrong feed.



Less possibility wiring fault.



The conventional block and intermediate Block system circuit can be incorporated in the SSI system circuitry.



More reliability accessories.



Less man power requirement due to high reliability components and self-diagnostic feature.



More safety.

due

to

less

relays

and

INTERLOCKING REQUIREMENT System consists of the following: 

Microprocessor based interlocking equipment to read the yard and panel inputs, process them in a fail-safe manner as per selection table and generate required output.



System consists of processor module, vital input and vital output modules, communication module and power supply module. System has facility of hot standby modules for better availability.

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

Control-cum-indication panel (domino type) with panel processor having stand by processor or VDU control terminal as required by purchaser. Control-cum-indication panel shall confirm to CL.3.0 of IRS: S 36. It shall be provided with push buttons/control switches for individual operation of points, clearing of signals, releasing of crank/ ground lever frame/ gate controls, cancellation of routes and other functions as covered by IRS:S36. Arrangements for route setting shall be provided



Maintainers terminal with display, keyboard, printer and event logging facility for mini. 100,000 events.



Relay rack along with required no. of approved types of relays or object controller.



Object controller to directly operate the field equipments like point machine, signal etc or relay interface to drive the existing field equipment.

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6

DESIGN FEATURE One of the following architecture may be employed in the system. i) Single hardware architecture with diverse software(s). In addition hot standby processor/ system may be provided with facility of automatic changeover in case of fault in working system without affecting train operation. a)

Without any Standby

Panel

SSI

Field

Fig No. - 1 b) With Standby ( Two SSI connected in parallel)

Panel

SSI 1

SSI 2

Relays

Fig No. - 2

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ii) Two out of two hardware architecture with identical or diverse hardware and common or diverse software. In addition hot standby processor(s) /system may be provided with facility of automatic changeover in case of fault in working system without affecting train operation. Dual Hardware (2 out of 2) with similar software a)

Without Stand by

Panel

I/ O

CPU 1

Panel Processor

CPU 2

Relays

Fig No. – 3 b) Panel

With Warm Stand by Panel Processor

CPU 1 CPU1

CPU 2 CPU 2

I/O Relays

Fig No. - 4

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8

With Hot Stand by

Panel

CPU 1 CPU1 I/O

Panel Processor

CPU 2 CPU 2 I/O

Relays

Fig No. – 5 d)

Panel

With Object Controllers

CPU 1 CPU1 Communication

Panel Processor

OC2

CPU 2 CPU 2 Communication

OC1

Fig No. - 6

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9

Two out of three hardware architecture with identical or diverse hardware and common or diverse software.

2 Out of 3 Architecture a) Pane l

With Relay Interface Panel Process or

CPU 1 CPU 2 CPU 3 I/O

Relays

Fig No. - 7 b)

With Object Controller Panel Processor

Panel

CPU1 CPU 2 CPU 3 Communication

OC

OC

OC

Fig No. - 8

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10

FAIL SAFE FEATURE 

The system is designed on fail safe principles. In case of any failure whether in the hardware, software or any part of the equipment, the system and the equipments controlled by fails on safe side and the system change over to a more restrictive state.



Any single failure results in an unsafe condition then the system changes to a safe state as soon as failure occurs.



The design of the equipment is cater for detection and restoration of system to a safer state in case of following faults if these are likely to results in unsafe condition. i) ii) iii) iv) v)

Variation in power supply beyond its tolerance limits, including momentary failure of the power supply system. Spikes in the power supply system, stray fields caused by traction vehicles or standby diesel generator sets. Insertion of PCBs in wrong card slots Earthing of any component of wire or a combination of such earthing faults. Broken wires damaged or dirty contacts, failure of a component to

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energise loss of power supply or blown fuse etc.

7.



The equipment is constructed to prevent unauthorised access.



Optical isolation of inputs.

SYSTEM DESCRIPTION 

7.1

The following SSI system may be used.

Single processor system- MICROLOK MICROLOK is microprocessor-based logic controller designed specially for rail road vital interlocking applications. Its basic function is to process various inputs according to a programme designed by the application engineer and create the appropriate outputs. Input and outputs may be through direct interfaces with MICROLOK or through serial communication with other vital or non-vital controllers. Direct inputs include track circuit occupancy, state of switch point machine contacts. Outputs eventually interface to control signal mechanism drives, signal lamp drives, switch control contractors and traffic line control circuits.

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MICROLOK incorporates two types of software: One is the special application programme developed by the user. The second type of MICROLOK software is the standard, executive logic common to all MICROLOK systems. This software contains routines designed to: a)

Verify the states of vital inputs and outputs

b)

Insure that all vital outputs are fully controllable

c)

Remove power to vital outputs in all cases where system failure has occurred.

More than one MICROLOK unit can be linked through serial communications to from a single system, using a Master/Slave communication protocol. Up to 16 slave units may be controlled by a master MICROLOK unit. 

The Microlok II system consists of following modules ♦ ♦ ♦ ♦ ♦ ♦

Hardware Design Installation Hot standby Maintenance Fault finding & Troubleshooting

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Hardware: Basic Microlok-II equipment consists of:       

Card file CPU PCB Power Supply PCB On-vital input / output PCB Vital Output PCB Vital Input PCB & Vital Cut Off Relay (VCOR)

Card file Each Card file consists of:  20 slots to accommodate various cards that are used in the system  A mother board connecting all the 20 slots CPU PCB  Each card file will have one CPU Board and it is placed always in slot No. 18 & 19.  The processor used in CPU is Motorola 68332 chip.  The processor is working at a speed of 21Mhz.

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 Each CPU is having 5 serial ports to connect the MLK-II to other MLK-II or other equipments such as Computers. Port 1 & 2 are RS 485 type, Port 3 is RS 432 type, Port 4 is RS 232 type & port 5 is used for Maintenance tool. The following are the functions of CPU:  Continuous monitoring of Vital board status  Continuous Diagnostic test to check system healthiness  Processing the equations based on the inputs received  Storing the Datalogging information Power supply PCB  Each card file will have one PS PCB and it is placed always in slot No. 16 & 17.  The PS PCB is basically a DC-DC converter, which converts the 12V DC supply of system voltage into +12V, -12V & 5V to provide the supply required for various boards used in the system.  Based on the diagnostic test done by the CPU and receipt of 250Hz pulse from the CPU, PS PCB extend the voltage to VCOR coil and energise the relay. Non vital input/ out put PCB

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 Each Non-Vital I/O PCB is having 32 inputs & 32 outputs.  The inputs are connected normally to the Panel buttons.  The outputs are connected normally to the Panel indications, counters & buzzers. Vital Output PCB  Each Vital Output PCB is having 16 outputs.  Each output is assigned to the final relay which is driving the outdoor signalling gears such as HR, DR in case of signal & WNR, WRR incase of points.  Since the output boards are driving outdoor gears, they are continuously monitored by the CPU and any abnormal voltage present in the output will lead to system reset / shutdown to ensure safety. Vital Input PCB  Each Vital Input PCB is having 16 outputs  Each input is assigned to the detection of outdoor gear status such as ECRs in case of signal, WKR incase of points & TPR in case of Track circuit.  Since the vital inputs are dealing with the detection of outdoor gears they normally configured with double cutting arrangement. VCOR Relay

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 Each card file will have one VCOR to ensure the healthiness of the system.  The pickup condition of the relay ensures the healthiness of the system.  The power to the vital output boards are extended through the VCOR front contact and incase of any error in the system will make the VCOR to drop and in turn will cut the power to the Vital output boards and ensure safety.  The VCOR relay is having 6 sets of dependent contacts and each contact rating is 3 amps. MLK-II wiring hardware The following are the wiring materials of MLK-II:  48 pin Address select PCB  96 pin Address select PCB  48 pin Connector Assembly  96 pin Connector Assembly  EEPROM PCB  Keying plug 48 & 96 pin address select PCB  Each address select PCB consists of 6 Nos. of jumpers.  Each slot will have its own jumper setting and each one is different from others.  The address select PCB ensures the type of board used in the slot as defined in the application logic. Solid State Interlocking CAMTECH Handbook No.ST-34

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 48 pin address select PCB is used for vital boards & 96 pin address select PCB is used for non-vital boards. EEPROM PCB  The EEPROM PCB is placed on the 48 pin connector assembly of the CPU PCB.  The purpose of the EEPROM PCB is to store the temporary data that are entered through the system configuration of Microlok-II maintenance tool package. Keying plug  The purpose of the keying plug is to avoid insertion of wrong type of board in any slot.  Each slot requires 6 Nos. of Keying plug and is to be inserted according to the type of board to be used in each slot.  In principal the keying plug is similar to the index pin of relays. Design  The Microlok-II design consists of 2 parts namely: ♦ Interface design, which consists of complete wiring details and drawings ♦ Application logic, which consists of complete interlocking program.

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Inter Face Design To prepare the interface design, the following inputs / drawings are to be provided by the customer to firm:      









Approved SIP (Signal Interlocking Plan). Approved panel front plate drawing IPS scheme. Relay room building plan. CTR, Block & Axle counter cable termination details. The SIP gives the clear picture of outdoor gears that are involved in the station such as signal, point, track, etc. to calculate the vital input and output bit requirement and relays requirement. The panel front plate drawing gives the clear picture of number of controls and indications that are available in the station to calculate the non-vital input & output bit requirement. Based on the calculation of vital, Non-vital I/O boards & relays, IPS scheme to be cross verified for the capacity & power distribution is to be made accordingly. Based on the calculation of vital, Non-vital I/O boards & relays, the number of racks to be calculated and placement of rack is to be made as floor plan to accommodate the racks with in the building area. The CTR, Block & Axle counter termination details gives an indication to designer to plan

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the interconnection between various racks and panel without any crisscross in wiring. The following are the steps to be followed in Interface Design:  Calculation of vital & Non-vital I/o boards including relays and its type  Calculation of MLK-II materials  Configuration of SSI  Floor plan  Complete wiring drawings

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Example of I/O calculation Gear Signal 3

V. O/p DR. R

POINT

WNR

TRACK

-

V. I/p DECR HECR RECR NWKR RWKR TPR

NV.I/p GN

Relay ECR-3 QNN1-1

WN

NV.O/p DGKE HGKE RGKE NWKE

-

TKE-W

QNNA1-

QNNA1-1

Calculation of Boards & Relays  As per the above example, the complete calculation of Vital & Non-vital I/O calculation is to be made for the station from the SIP & Panel front plate diagram.  The total number of vital input bits is to be divided by 16 and number of board to be calculated.  The total number of vital output bits is to be divided by 16 and number of board to be calculated.  The total number of non-vital output bits is to be divided by 32 and number of board to be calculated.  The total number of non-vital input bits is to be divided by 32 and number of board to be calculated.  Since each non vital board is having 32 inputs & 32 outputs, whichever board is coming at higher side only to be considered for slot requirement.  The total number of vital & non-vital boards are to be added and divided by 16 to determine the number of card files required.  Based on the number of relays calculated and the capacity of the relay rack decided, number of relay rack required to be calculated. Solid State Interlocking CAMTECH Handbook No.ST-34

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Calculating other materials of MLK-II  The 48 pin connector assembly required is the sum of vital I/O PCB + CPU + PS PCB  The 48 pin address select PCB required is the sum of vital I/O PCB.  The 96 pin connector assembly required is equal to number of non-vital I/O PCB  The 96 pin address select PCB required is equal to the number of non-vital I/O PCB  Each card file will have one CPU, one PS PCB & One VCOR  Each CPU will have one EEPROM PCB Configuring MLK-II  The configuration of single MLK-II with VDU, Maintenance PC is shown in the fig no. 9.  The boards are to be placed in the card file as: ♦ Non-vital I/O PCBs as first set ♦ Vital output PCBs as second set ♦ Vital input PCBs as third set ♦ PS PCB in slot 16 & 17 ♦ CPU PCB in slot 18 & 19 ♦ Empty slots are to covered with 1” wide blank plate for dust proof. SM room Relay room

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Panel

P1

P2 P1 P2

MLK-II

P5

M.PC

P1

VDU

P3

P4 RELAYS

Fig No. - 9  The VDU will be connected to MLK-II through CPU serial port  The Maintenance PC will be connected to MLK-II port 5 to access the MLK-II maintenance tool package.

Floor plan  After doing the calculation & configuration the number of racks to be calculated to draw the floor plan for accommodating the racks  The following are the racks used: ♦ Microlok-II Rack: 2100mm X 800mm X 600mm – Capacity to fit 2 card files ♦ Relay rack: 2100mm X 1120mm X 300mm – Capacity to mount 96 relays ♦ Panel termination rack: 2100mm X 700mm X 300mm – Capacity to wire 11 Non-vital boards

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Inter face circuit design Based on the above details prepared the interface circuits will be designed. The interface circuit drawing consists of:                 

Index Signalling layout plan Panel front plate drawing Control table Floor plan Configuration Serial port wiring details Address selection, Jumper setting & Keying plug details. CPU & PS PCBs wiring. I/O bit chart. Non-vital & vital boards wiring. Signal lighting, Point driving, Axle counter, Block wiring. IPS scheme & Power distribution Fuse chart Racks assembly drawings Inter connection details Contact analysis

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Application Logic Design  The application logic contains the complete interlocking of the station.  The input required to design the application logic is control table.  The Application logic is written in Boolean equation.  The application logic is divided in to 4 parts: ♦ Non-vital section ♦ Vital section ♦ Timer section ♦ Serial section

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Comparison of PI vs SSI circuit SEQUENCE

TPRS

GN+UN

STATUS

UP

FROM PANEL

UP

HECR

HR

SEQUENCE INDICATION

STATUS

TO PANEL

FROM FIELD

GNR +UNR GNCR,UNCR

TO FIELD

NRR

NNR

DOWN

UP

DOWN

WLR

ALSR

DOWN

DOWN

WNR/WRR TO FIELD

UCR

WKRS

UP

FROM FIELD

PI CIRCUIT SEQUENCE

TPRS

GN+UN

STATUS

UP

FROM PANEL

SEQUENCE INDICATION

STATUS

TO PANEL

HECR

FROM FIELD

WNR/WRR

INSIDE SSI

TO FIELD

HR

INSIDE SSI

TO FIELD

WKRS FROM FIELD

SSI CIRCUIT

Fig No. - 10

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 From the above, it is clear that the number of relays required for PI is more & MLK-II is less.  MLK-II requires only field detection relays such as TPR, WKR & ECR as input & driving relays such as HR, DR, WNR,WRR as output.  The other internal interlocking relays are stored in side the memory of MLK-II CPU and are called Boolean bits. Non Vital Section  The non-vital section consists of button relay circuits & indication circuits.  The names of relay used for this section will be defined in non-vital I/O boards / NV Boolean bit section in the application logic.  The equations for non-vital circuits will be written in logic as Nv. assign statement.  The vital section consists of all other interlocking circuits.  The names of relay used for this section will be defined in vital I/O boards / Boolean bit section in the application logic.  The equations for vital circuits will be written in logic as assign statement.

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Timer Section  The time delay required to pick-up / Drop the relays will be written in this section.  This similar to condenser, resistor circuit in PI circuit.  For slow to pickup the time will be defined as Set & for slow to release the time will be defined as Clear. Serial Section  The relay conditions used in one MLK-II will be transferred to other MLK-II or to VDU computer will be defined in this section.  The input bits of one section is to be written as output bits of other section and order of bits should be one to one matching. Symbols used in application logic  The following are the symbols used in application logic:  * Series  + Parallel  ( Start of Parallel path  ) End of Parallel path  ~ Back contact  , Separation of bits  ; End of statement / section

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PI circuit Vs MLK-II Logic PI circuit A

B

C

E

D Fig No. - 11  The above circuit will be written in application logic as: Assign A * B * (~C + D) To E; Compiling the application logic  Once the application logic is completed, using MLK-II compiler the application logic will be converted into machine language.  This will be loaded into the CPU of MLK-II through MLK-II maintenance tool using software upload command.

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Installation  Once the number of MLK-II equipment & Relays are calculated, number of racks required to be calculated.  The racks are to be placed in such a manner that the relay racks are to be kept nearer to power supply room side & panel termination rack nearer to SM room side. Wiring  The Non-vital boards wiring are to be terminated to panel termination rack. The panel is to be connected to panel termination rack through inter connection cable.  The vital boards wiring are to be terminated to Relay rack and then to relay coil / contact.  The CT Rack functions are taken to Relay rack through inter connection cable.  The various supplies available on IPS are brought to Relay rack, MLK-II rack, etc. according to the requirement and provision made on each rack through power wire.  Serial cables are used to connect between MLK-II equipments, VDU & Maintenance PC with MLK-II equipments.

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Testing Once the wiring is completed, the following test are conducted before commissioning the station.  Bell test – to ensure the correct continuity  Wire count test – to ensure unwanted wires are not present in the system.  Simulation test – to ensure the interlocking is made as per the control table requirement. Commissioning  Once the simulation test is completed and ensured, the indoor equipments are connected to the outdoor gears directly and tested from the panel for proper working of station interlocking.  Once the operations are found satisfactory, the equipment is handed over to traffic for regular operation and ensures commissioning is completed. Hot stand by The purpose of Hot standby is to increase the availability of the system for traffic during the failure of indoor interlocking in one of the equipment.

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MLK-II Hot standby system Hardware  In MLK-II for each station two sets of equipments are used to achieve hot standby function and named as System A & System B.  MLK-II hot standby uses 100% hardware redundant including I/O boards. All Vital & Non-vital both inputs & outputs are connected in parallel to the common equipments to achieve when one equipment fails the other system to retain the interlocking status without any interruption to the signalling. (smooth changeover)  All vital inputs, Non-vital I/Os are connected through 1 in 2 out terminals to take the same inputs & to drive the same indications on the panel.  All vital outputs are connected through diode terminals to common output relay coil to avoid any reset happening due to other system output voltage available in the terminal. Software  The interlocking portion of application logic is common for both Systems A & B.  All the Vital & Non-vital inputs received by both systems get compared using serial bits for input status at all the time to ensure both systems receiving same inputs and to avoid any processing of wrong outputs.

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 Similarly, the outputs processed are also get compared using serial bits before delivering the final output to avoid any mismatch in output.  The standard configuration for an hot standby system is shown in figure below. MLK-II Hot standby configuration

Operator VDU

SYSTEM A

Maintenance VDU

SYSTEM B

Panel

Vital Input & Output

(Output via Diode terminal)

Relay Rack Serial Parallel

Fig No. - 12 Factors considered  Being as physical inputs and wiring, any wire cut in one system will made to behave in the following manner:  Vital Input : In case of wire cut in one system, the equations are made to kill the other system and to retain failure for the particular input related routes.  Non-vital Input: In case of wire cut in one system, the equations are made to kill the same system and to make the availability of interlocking through healthy system.

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 Any physical wire cut in outputs will not lead to system shut down / kill. The vital output contacts are read back on the non-vital input through relay contacts to detect that the false feed given to any vital output related relays. In case of false feed, both systems will reset and reason for reset will be recorded in the system error log. Maintenance  MLK-II based SSI contains standard windows based Microlok-II Maintenance tool package loaded in the Maintenance VDU.  The various facility available on MLK-II maintenance tool and its purposes are below. ♦ Free run variable : By selecting this, user can visualize all the relay names that are used in the application logic and their status. ♦ User Data Log: The relay names that are entered in the Log bits section of User data log to monitor its changes will be stored in the memory. User can down load the information from CPU and can analyze the cause of failure. ♦ System Event Log: By selecting this option, user can see the events that are happened in the system such as Reset, Serial communication establishment time, etc. ♦ System Error Log: By selecting this option, user can see the errors that are present in the system such as Board failures, system killed by application logic,etc.

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♦ Merged Events Log: This will provide the combination of all the 3 logs information in graphical manner. ♦ Set time of Day clock: Using this option, the present date & time of MLK-II can be set to monitor the Logs with exact date & time. ♦ Software upload: The compiled version of MLK-II application logic is to be uploaded in to the CPU through this option. ♦ Reset Microlok-II: Using this, the MLK-II can be reset. In case of MLK-II is gone to sleep mode due to hardware failure, the CPS can be made up by using this option. ♦ System Configuration: This option is required to disable the boards to test the hardware, adjust time delays during testing, etc. ♦ Serial Message Monitor: By selecting this option, the communication ports status can be checked for their healthiness. ♦ Software down load: From the CPU compiled version of present working application software can be down loaded.

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Other Maintenance related to SSI  The equipment should be kept clean from dust.  All wires that are terminated on the terminals are to be checked visually and any loose connection that are found to be tightened.  The batteries that are used with IPS are to be maintained properly, as per Railway practice.  The User Data log information is to be down loaded from CPU & to be stored in Hard disk atleast once in a week. After checking that file is saved properly, the data log is to be cleared. 7.2

Two out of Two SSI system

In two out of two systems, two processors receive the command and process it for output generation. The output command is compared first and if matches then only output is energised. There are so many systems available world-wide which has different architecture and modules depending upon manufacturer to manufacturer. Here we are describing the indigenous system developed jointly by RDSO, DOE and IIT, Delhi.

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Indigenous system consists of following      

 

CPU card ( 2 nos.) Relay read interface card (RI) Voltage monitor card (VM) Comparator card (COMP) Relay driver card (RD) Panel processor a) CPU Card b) Relay read interface card c) Indication driver card Data logger Maintainer’s terminal Operator’s panel. Panel Processor CPU 1

Operators Panel CPU 2

Field Inputs

Read Interface

System Bus

Voltage Monitor

Comparator

Relay Driver

Field Inputs

Fig No. - 13

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Empty slot

spaceEmpty card

spaceEmpty card

COMP - 6

COMP – 5

COMP – 4

COMP - 3

COMP – 2

COMP – 1

space Empty card

spaceEmpty card

MULTI OUTPUT DC/DC CONVERTOR

Empty card

RICARD-5

RICARD-3

VKCARD

PRO-2

PRO-1

RICARD-2

RICARD-1

RICARD– 4

space Empty card

DC-DC CONVERTOR

EMPTY SPACE MULTI OUTPUT DC/DC CONVERTOR UNIT EMPTY SPACE

Fig No. - 14

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spaceEmpty card

spaceEmpty card

spaceEmpty card

RD - 6

RD – 5

RD – 4

RD - 3

RD – 2

RD – 1

space Empty card

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SOLID STATE INTERLOCKING SYSTEM

EMPTY SPACE + 10 V

+5v 0.75 A

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Hardware details CPU card This is the main processing card of the system and uses Intel 8086/8088 microprocessor. There are two type CPU cards in the system. Processing is done independently in each of the two cards. The system follows two out of two logic. Read Relay interface Card This card acts as an input interface to the system from the input relays. The input to the system comes from various fields relays like track circuits, point status relays, signal lamp proving relays, button inputs from the operator’s panel and read back of output relays. This card also isolates the system from the field relays circuits. Provision has been kept for testing of malfunctioning of the system in reading the status of the relays. Each card can read 48/64 input relays. Inputs are isolated using opto couplers. Comparator card This card is use for executing the two out of two logic. The main function of the card is to compare the output of the two CPU cards and give appropriate signals to the relay driver card. Each card caters 8 channels.

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Relay driver card This card acts as an output interface of the system to the field gear controlling relays for points, signals, level crossing, crank handles etc. are driven by this card. Each card can drive 8/12 relays. In order to isolate electronic circuitry from field equipment, transformer isolation is provided. In new design relay driver card incorporate comparator card function itself. Voltage monitor card The purpose of this card is to monitor various voltage levels in the system. There are 4 Vcc supplies in the system. Change in the operating voltage of the ICs can severely affect the performance of the system. VM card detects any deviation from the allowed safe operating condition. In case of any fault in the system, SSI is brought to a safe shut down by switching off shut down relay thereby withdrawing power from relay driver output. Software details The Solid State interlocking consists following: a) System software is universal and independent of yard layout. b) Yard data derived from the locking table / selection table of the given yard. The SSI system Solid State Interlocking CAMTECH Handbook No.ST-34

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software can be broadly divided into following parts. Input Read Module This part of the software reads the input information coming from the interface relays and operating panel. After proper debouncing, the data is stored in the memory. Panel Processor module This part of the software reads the panel command coming from the operating panel and decides the action to be taken for these commands, e.g. Route setting, point operation etc. Route controller module This part of the software receives commands from the panel processor and decides the action to be taken for these commands, e.g. route setting, point operation etc. Signal controller module This part of the software receives commands from the route controller for the signal clearance. It checks the signal aspect chart, condition of the signal ahead and decides the aspect for the particular signal. Depending on the decision taken, command for picking up the aspect control relays viz., HR, HHR, DR is given by this software. This part of the software is also responsible for checking the reconciled status of the Solid State Interlocking CAMTECH Handbook No.ST-34

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signal viz-a-viz last command given for signal clearance. Point and Slot Controller Module This part of the software accepts the commands coming from the panel processor as well as from the route controller (in case of automatic route setting facility), examines whether the point operation is permitted by the interlocking and issues command for picking up of the point operation relays i.e. WNR/WRR. Track locking of the point is also checked. This is also responsible for logical locking of the point in the route and makes the reconciled status of the point viz last command given to the routine. The controlling relays WNR/WRR are energised only for the required time and after setting of the point these relays are de-energised. Ground frames, crank handles and level crossings are also controlled by this routine. Supervisory Routine Module In this hardware, two microprocessors have been used for safety reasons. The supervisory routine ensures safety of operation by self-checking of the CPUs and other associated hardware. CPU self-checks include RAM/ROM check. The other hardware is checked for proper addressing / accessing of the data and correctness of the data. In case of a major failure is detected in the CPU / associated hardware, safe shutdown of the whole system is performed. The failure is indicated on the Solid State Interlocking CAMTECH Handbook No.ST-34

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display panel, so that the maintainer can take up corrective action such as replacement of a card. Thereafter, the system can be re-started after rectifying the fault and pressing the reset and restart button. Counter have been provided for registering resetting operations. 7.3

Two out of Three SSI system

The system consists of following sub system    

Central Interlocking Unit (CIU) Panel processor module and operator’s control cum indication panel Object controller (OC)

Central Interlocking Unit (CIU) The central interlocking unit consists of processor (3 nos.), power supply modules ( 2 nos.), communication module as under: a) Processor module (3 nos.) System is designed with triple redundant processor modules, which is normally work in 3 out of 3 mode. Processor modules continuously check its own health as well as health of other modules and ensure proper working of all components used in the card. It also check the voltages to various modules. In case of fault in one CPU module, concerned module is isolated and system work in 2 out of 3

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mode. In case of fault in two CPU modules then system will shutdown. b) Two powers supply modules (DC DC Converter) to ensure high availability. c) Two vital communication modules working on two different communication cables in hot standby mode for failsafe communication with object controller (s). The communication protocol shall meet the requirement of CENELEC specification EN 50159. d) Non vital communication module for communication with panel processor. e) Power supply for CIU 24 volts DC +30% - 20% The equipment is a processor based working on 2 out of 3 architecture with sufficient ports for interfacing with: a) Panel processor(s) with in 800 meters. b) Object controller(s) up to 15 kms radius c) Other EI equipments for block working block equipments of suitable design kept up to 15 kms. d) Data logger e) CTC f) ETCS (AWS) g) Printer h) Maintainer terminal

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Panel processor & control cum indication panel ♦ Panel

a)

b) c) d)

processor

Panel processor is to be kept near the operator’s panel. It is processor-based equipment to process operator’s control commands in the form of potential free contacts of panel button(s)/switch (s)/ key(s) and transmit to CIU on serial communication. The input reading mechanism is isolated from equipment supply and operate on an isolated 24VDC. Whenever an input is found present, it is debounced twice before accepting it as valid input and before transmission to CIU. The transmission of serial communication is on request from CIU. At any given time not more than two button contacts and 3 contracts( in groups) is required to be transmitted from panel processor. Receive indication for field gears from CIU and drive respective indication lamp (LED’s) on local control panel. Display health and error indications related to itself, CIU and object controller. Following modules is provided in the panel processor: Processor modules i) Input modules ii) Indication driver modules iii) Power supply DC DC converter

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iv)

e)



Communication module for communication with CIU The panel processor have ports to interface with i) CIU ii) CTC

Control cum indication panel: Control cum indication panel is to be domino type with push buttons. It is provided with push buttons for operation of points, clearing of signals, releasing of crank handle/ ground frames/gate controls, cancellation of routes and other functions as covered in RDSO specifications clause 3.0 of IRS: S36.



Object Controller i)

It is a processor based equipment with 2 out of 2 architecture. The equipment work as a slave unit of CIU through duplicated serial communication and placed within 15 Kms radius from CIU. It drives the field gears and take feed backs from various field gears. Object controller is normally provided in the field locations, however at small stations it may be provided near the CIU. In case of communication failure between CIU and OC (Object Controller), all the outputs are withdrawn to safe state with in 500 milli.sec.

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ii)

Object controller consists of following modules: a) b) c) d) e) f)



46

Point modules Signal modules Relay modules Input modules Dual communication modules Power supply modules

Output functions of object controller a) to directly drive the colour light signal(s) b) to directly drive point machine(s) and c) to directly operate electromagnet relay(s) of QN type ( for ground operated points, level crossing and slotting)



Input functions of object controller a) Serial communication from CIU to receive the command to drive the required field equipment( Signal/ Point/Relay and or health signal). b) Transmission of status of the field gears to CIU. c) To read external inputs. d) The following parameters are to be ensured for reading an external input;  It should sense potential free contacts through an isolated supply of same voltage as the working voltage of the system.

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















47

The input detection mechanism should be optically isolated to have a physical isolation to internal circuits. The system should be able to read the DC Positive and Negative from an external input to have a double cutting feature. Whenever an input is found present, it must de-bounced a minimum of 3 times or more @ 20 milli-seconds before accepting it as valid input and onward transmission to CIU. Once an input is accepted, it should be treated as absent when it is not available twice @ 20 milli-seconds (min.) and 50 milli-seconds (max.) for onward transmission to CIU. A fail safe test should be performed on every input to test the performance of all components used in detection mechanism by any one of the methods:-

Using a toggle test on each input which is found present, by turning it to absent internally at input level or Using a short circuit test on each input that is found present, by turning it to absent internally at input level. The short circuit should not directly come across input potential and should be through a protection mechanism or Removing the bus bar supply to read the potential free contacts and reading the input as absent or

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Any other method acceptable to purchaser to ensure the fail safety. e) The following parameters are to be ensured while reading a feed back of an output for signal controller

 



The AC current to each lamp should be perfectly sensed through a current transformer for aspect to be lit. The DC current may be measured by resistance drop method. In both the cases the potential should be transformed in to a digital input using Analog-Digital converter or voltage to frequency converter and fixing the acceptance or rejection of input through software as per the working ranges given in signal controller.

Advantage of Object controller a) Saving of cable b) Reduces no. of relays c) Reduces power consumption

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Supervisory function Supervisory module checks/ check proper levels of system voltage(s) at critical points to ensure proper working of all components used in the system. It also checks the health of compete object controller system. Any error in system or hardware fault leading to unsafe conditions, will withdraw all output commands and remove the source supply to outputs modules.



Features of Signal Module It is possible to operate two signals by a signal module. It is capable to control 8 electric signal lamps. Two of these lamps are designated as ON aspect lamp and others as OFF aspect lamp(s).  Output i) ii)

iii)

A LED electric signal lamp operating at 110 V AC and current of 125mA nominal subject to a maxi. 200mA. The circuits for ON aspect is so designed that due to any failure of object controller or communication failure between CIU and OC concerned, ON aspect lights up and power supply to all OFF aspects should withdrawn. The circuit for OFF aspect is so designed that it should remain lit till processors are active and getting command from CIU continuously in each cycle. OFF aspect should extinguished without fail in case of any

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♦ Processors getting faulty ♦ No communication from CIU iv)

Whenever an OFF aspect is not lit due to any reason, ON aspect must light up without fail. The overload protection is provided for each output and if output current is beyond the specified limits then overload protection circuit comes in action an alarm is generated in CIU.

 Input a) Each aspect has taken as lit at 90 mA and once taken as lit and as not lit when current drops below 60mA.When the current exceeds 200 mA the command to the lamp is withdrawn and lamp of next more restrictive aspect will lit up. This fault will be reported to central interlocking unit. b) The facility to read back the potential @ 1224 V DC from actual signal head condition is provided.  Cascading of aspects



Whenever the lamp of an OFF aspect is not lit after the specific command or over current is detected, the power to output circuit is withdrawn and information sent to CIU as well as generate the local command to switch on the ON aspect till command to lit another aspect is received. Point Module

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It control the power to 4 different point machine for each of them with two different settings i.e. Normal and Reverse. On completion of operation end of operation feed back is received from point machine and communicated to CIU, which in turn withdraws point operating command.  Output i)

Each point machine operates at 110 V DC and maxi. Current 7.5 amps. It is presumed that a point machine may take a momentary current of upto 15 amps. for a short duration of 100 milli. Seconds. ii) For safety reasons every point command consist of: a) First command for either Normal or Reverse setting to actuate solid state contactor followed by b) Second command to operate the point motor by operating a common electromagnetic relay(contactor relay, WR). This command will be transmitted from CIU on getting feedback for the first command. iii)

The overload protection is provided for each output and if output current is beyond the specified limits, overload protection circuit comes in action an alarm is generated in CIU.  Input The feed back from a point is always in terms of DC supply of 24 V DC and each point may have 2 or 3 input namely: Solid State Interlocking CAMTECH Handbook No.ST-34

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52

NWKR for normal setting of point RWKR for reverse setting of point ZWKR for end operation of point

In addition to above the contactor relay's (WR),front contact feed back is provided. 

Relay Module To derive 8 nos. of 24VDC relays each with coil load between 215 Ω to 400 Ω isolated 24 V DC is use to energise output relays. Each such relay will be read back in to the system by reading external 24 V DC Power supply over its front contacts.



Input Module It reads 12 nos. of external input from 24 V DC power supply.

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8. Maintenance of SSI system Maintainer must have a thorough understanding of these systems, general operating system. Maintenance must be performed by properly qualified and trained persons. However a detailed knowledge of microprocessor based logic and system is not required. 8.1

General Maintenance i) ii) iii) iv) v) vi)

Make sure that all the equipments are properly fixed in rack with the help of screws. Ensure that earth is properly connected with SSI system rack and thick wire used for earth connection. Ensure that power supply to DC DC converter is given through fuse and rating of the fuse is between 7-10 amperes. Ensure that power supply at DC DC converter end is between 21.6 to 31 volts DC when charger is in OFF condition. Ensure that AC ripple of battery charger is less than 50 mV. Ensure that all relays are fixed and clamped properly.

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9.

Do’s and Don’ts

9.1

Do’s i) ii) iii) iv) v)

9.2

54

Before any types of maintenance, make sure that there is no train in the section. Before removing any card ensure that DC DC converter is off. Before inserting any card, ensure that you are putting the card in its correct slot. Connect the 24 volts +ve and –ve supply as per the power requirement stipulated and specified units. Externally accumulated dust must be removed with vacuum cleaners.

Don’ts

Replace any card when the system is ON. i) Use any kind of solvents, detergents or abrasive cleaners on the card file or internal components. ii) Use vacuum cleaners inside the card file. iii) Switch on the supply without ensuring the correctness or input or the respective LED’s are glowing.

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Error Coding

The system has unique feature of self diagnostic by which any discrepancy in the system is displayed in the form of Alarm / Error. In the case of ALARM the system displays the alarm code but continued to function in normal mode. In the case of ERROR the relevant error code is displayed and the system is automatically brought to a safe shutdown. ERROR/ALARM codes are differs manufacturer to manufacturer. Some of the typical ERROR/alarm codes are given below: ALARM ALARM

Description

1. A 201

Output relay expected to be picked up but it is actually dropped.

2. A 300

Remedy

Check the cabling to the distribution mother board. Check whether the concerned out put has actually picked up. Then the problem is with the relay input card or read back input may not be reaching. Refer the stations input /output map chart for the faulty input card. Replace the same. A push button is Check if any push button is stuck up in the stuck up in the panel. Check pressed whether the RI cards are condition. outputs in the right slots. If not then replace the card .

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ERROR ERROR

Description

1. E503 to 505

Power failure

2. E 480

3. E 507

4. E 508

Remedy

supply Check the +24 v power supply. Check whether the VM relays are mounted properly. If error repeats replace the VM card. Restart push Check for the cabling from the button stuck up push button to the nine pin D type connector. If the error still persists replace the concerned CPU card. Faulty safe shut Check for proper mounting of down circuit in VM card. If error still persists VM card unable replace the VM card. to switch off power supply to VM card Faulty safe shut Check for proper mounting of down circuit in VM card. If error still persists VM card unable replace the VM card. to restore power supply to VM card

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Failure statistics : Failure statistics of SSI microlock on SC Railway as on 31.07.00 Name of Total station failure KYZ 111 SVPM 53 TTU 15 UPD 21 VTM 8 TNR 11 SDM 12 KRV 5 SKM 3 OGL 2

Service months 72 66 58 55 41 40 37 27 13 5

Failure/ month 1.54 0.803 0.25 0.38 0.195 0.275 0.324 0.185 0.230 0.4

Failure/ year 18.05 9.636 3.103 4.581 2.341 3.3 3.89 2.22 2.76 4.8

NO OF STATION=10 FAILURE PER MONTH=241/414 = 0.882 FAILURE PER YEAR = 6.98

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58

Comparison of various SSI architecture

Architecture

Known world wide su ppliers

Single hardware

a)

Dual hardware redundancy

a)

US & S (MLKII) b) Alstom (VPI)

b) c) d) e) f) g)

Triple modular redundancy

Bombardier (EBILOCK 950) AZD Phara (ESSAII) Nippon Signals (EI32) Kayosan Siemens (SICAS S-5) Alstom 9Safe lock) CGL SSI

Alcate (Estwl90) b) Simens (SIMIS) c) Simens (SICAS) d) Alstom SSI e) Alstom (ASCV) f) West race g) Geologic

Software Standard/ validation US MIL 882 C ORE

World wide installation

CENELEC CENELEC RTTI/Japa n German Standard DIN V-19250 RDSO RDSO

Zech Rly Japannes , turkey -doGermany China Thialand Korea India India

a)

Cenelec Cenelec standard BRS BRS SIL4

USA, Australia, Sweden, India Malesia, Bangladesh

Romania Nietherland Germany UK China Thialand Korea India India



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