Solid State Interlocking- Preparation of Estimate and Schedule

1. Solid State Interlocking-Preparation of Estimate and Schedule Ashok Kumar Manager/S&T Rites Ltd. ashokdudeja2001@gmail.com

2. Consideration of yard for SSI • The outdoor arrangement is same in most of the cases for a station with SSI or without SSI. • The signalling functions which control field gears is taken as vital outputs • The signalling functions which are received from field are vital inputs • Also some inputs/outputs connected to block instruments are vital • The key-in position of Crank handle is also a vital input

3. Consideration of yard for SSI • All the control commands coming from panel are taken as Non-Vital inputs. • The indications, counters, buzzers etc are taken as Non-Vital outputs

4. Power Supply Arrangements Depending on the type of SSI being installed the power supply arrangement will differ for different make of SSIs. For example – Microlok II uses 24v DC Other manufacturers may use different voltages like Siemens and AZD Praha Accordingly the requirement of power for the SSI working to be catered in the IPS or separately created

5. Assessment of Interface with SSI Vital and Non-vital I/O bit calculation Vital and Non-vital board calculation System configuration and serial communication Power calculation Interconnection of various racks and interlocking equipment Manuscript of complete wiring diagram

6. Vital Input and Output PCBs No of Vital Outputs per output card No of vital inputs per card Suitable for 12V , 24V or 60V DC application. Spare vital inputs and outputs

7. Non-vital Input/output PCB Each Non-vital I/O PCB has 32 inputs and 32 outputs in one PCB. Suitable for 12V or 24V DC application. Non-vital inputs are Panel push buttons and keys. Non-vital outputs are Panel indication LEDs, counters and buzzers.

8. Calculation of Vital I/O Bits Gather following information from Interlocking plan: Type of signals, no of aspects, Points / Cross over and type of control / operation Motor points / Hand operated points Level crossings, siding control and crank handles Track circuits Axle counters Block working and controls from and to the block instruments

9. Calculation of Non-Vital I/O Bits Collect the following information from Panel Diagram: Number of push button controls/knob controls and key controls. (if knobs are used one bit for normal and one bit for reverse position to be considered) Number of indications, counters, buzzers, bells etc All output relays controlled by SSI are required to be read back as per RDSO specification From this information collected from “Signalling Plan” and “Panel Diagram” Vital I/O and Non-Vital I/O bits can be calculated respectively.

10. Example of I/O Bits:

13. Calculation of Boards After finding out final quantity of Vital and Non-vital I/O bits, quantity of various boards can be derived : • Calculation of Vital Input, Output cards and Non-Vital input, output cards is not significant at initial estimate size, unless the tenderer quotes in the form of cards • It will be difficult to evaluate on the basis of cards • Only the total number of vital inputs/outputs and non-vital inputs/outputs can be projected, so that the requirement of cards is decided by the tenderer, as seen from the above the bits per card vary from manufacturer to manufacturer.

14. Configuration of SSI system • When the station provided with SSI is quite big, then more SSI units are to be provided and synchronised • In that case whether the all the SSI units are to be kept at one place or to be located at appropriate places to be decided • If requirement is to keep the SSI units at respective locations, their synchronising with the use of OFC or twisted pairs

15. Schedule for SSI system- Salient points • The SSI system should meet the latest RDSO specification and all mandatory requirements of the specification need to be complied by the supplier. • While preparing the schedule clear demarcation of work to be done by indoor(SSI) contractor and similarly the demarcation of outdoor contractor. As both indoor and outdoor contractors has to work clubbing outdoor cables to indoor wiring, this is necessary. • Requirement of material for indoor work to be specific and clear. • Requirement of relays for indoor work whether to include in SSI schedule or not to be decided. Where specific type of relays need to be used in that case procurement of such relays to be decided (in case of Siemens, Westinghouse etc)

16. Schedule for SSI system- …..contd • Power supply requirements of the SSI and their arrangement from IPS or individual supply. • Requirement of supplies for reading inputs, driving outputs and interface with panel for indications, buzzers, counters and button input reading to be decided. • Where more than one units are installed, requirement of additional equipment and synchronisation of the units through OFC or twisted pairs. In such cases cable paths need to be different from reliability point of view. • Grounding, Surge protection and Earthing of SSI equipment and measures to control EMI to SSI equipment. • Arrangement for protection from dust.

17. Schedule for SSI system- …..contd • Provision of data logger • Both the Hardware and Software should be to SIL level 4 • Spare capacity for expansion or alterations in the yard upto 20% and facility for future alterations • Training of staff right from maintainer • Sufficient spares for the defect of cards and power supplies as deemed necessary • The Software should be developed to Software engineering standard such as CENELEC with special application to safety critical application

18. Schedule for SSI system- …..contd • Requirement of system architecture • Single Hardware with diverse software • Warm standby • Hot Standby • 2 out of 2 system with • Warm standby • Hot Standby • 2 out of 3 architecture • Requirement of flexibility in application software • Any other requirements as per practice of individual railways

19. The End Thanks