Signalling Circuits Design Criteria Quiz

Design Criteria of Signalling Circuits

• Detailed designs for interlocking circuits may be required for route setting (entry/exit principle) or non-route setting (individual point operation).
• Designs must meet requirements for 25 kV AC electrified areas (as per Chapter 22 of SEM).
• Designs must align with approved signalling plans, control tables, control panel diagrams, and relay contact analysis/rack arrangements.
• Compatibility with various equipment (e.g., types of electronic interlocking, interfacing features) should be considered.
• Dual OFC in distributed electronic interlocking is desirable for reduced copper cabling and alternate failure paths.
• Designs must adhere to typical templates, RDSO standards, industry best practices, and principles of reliability, availability, maintenance, and safety.

Control Panels

• Illuminated diagrams on control panels must be well-proportioned. Domino panels are preferable where additional facilities are anticipated.
• Areas covered by each track circuit should be distinguished by different colours.
• Operating members (route switches, point switches, etc.) should be placed in geographical order on the illuminated diagram (or a console).
• Installations using individual point operation may be set on an 'entry/exit' principle.
• Route setting installations use two push buttons (one at the entrance, one at the exit).
• Non-route setting types use individual point operation.
• Signal clearing may involve individual push buttons, group buttons, or a common switch for concurrent signals.

Control Panel Indications

• Provision for individual point operation is mandatory.
• Records of emergency point operations (during track circuit failures) must be kept.
• Slotting facilities for connecting cabins, ground frames, and level crossings should be available.
• Cancellation of slot operations should accommodate a delay period for route holding or locked route status.
• Control panel operation must not impact the last operational setting of signalling equipment. Signals should be able to be returned to 'ON' without affecting route settings when the key is removed
• Displays of yard position, and important indications for maintenance personnel.

Point Indications

• Point position is indicated by white/yellow/green lights near switches and white strip lights in the point zone..
• During point operation, the corresponding point light should flash until it locks.
• Indicate locked point position with a small white light near the switch.

Route Indications

• Route setting and locking status is indicated using white lights (minimum two) on each track section.
• Complete route sections are illuminated with white lights when the route is correctly set.
• Route lighting changes to red while a train occupies it, then returns to white when clear.

Signal Indications

• Red light shows "stop" signal 'ON'.
• Yellow light indicates "permissive" signal 'ON'.
• Green/yellow/double yellow light signifies "OFF" signal aspect.
• Flashing green/yellow/red lights indicate signal aspect failure.

Track Circuit Indications

• Red lights (at least two) indicate track circuit occupancy.
• The lights extinguish when the track is unoccupied.

Power Supply Indication

• Indication of various power sources (mains, diesel generator, or catenary) should be given appropriately.

Other Indications

• Approach track circuits are displayed on illuminated diagrams.
• Advance approach warning of trains may include flashing lights and/or audible warnings. An indication should be provided to silence the audible warnings by a pushbutton.
• Signalling aspect/route aspect failure should be indicated by a red light.
• Ensure that a circuit failure results in the display of a most restrictive aspect.
• Control panel displays should show the 'locked' or 'free' status of crank handles.
• Displays should indicate if a CH key is present, and if the control is not taken from the control panel.
• The gate control status should also be displayed on the panel (e.g. Yellow Steady if closed/locked, Yellow Flashing if released but not open, Red Steady when open). Ensure there is a provision for a counter to operate.
• The current and appropriate relay and electrical considerations should be noted for return wires.
• Indicate whether an approved electronic flasher relay (other than mercury type) is provided.
• Clear representation of train detection and route locking criteria is displayed.

Route Setting Type

• The route setting and clearance conditions adhere to specific criteria.
• Ensure all points are set and locked. Overlaps and isolations are similarly addressed.
• Track circuits in the route and overlaps are clear and free from interference/faults.
• Signal stop aspects are not blank.
• Route interlocks are established electronically.
• Approach and dead approach locking for manual stop signals is a mandatory feature.
• Level crossings, ground frames, cabins, and sidings have interlocking mechanisms.

Non-Route Setting Type

• The points in the selected route, along with any required overlap and isolation, are positioned appropriately using switches or pushbuttons in conjunction with a group pushbutton.
• SM key is in.
• The interlocking is free.
• Points including hand-operated points within the route, involving overlaps and isolations (as applicable), are set, locked, and identified promptly.

Route Release Circuits

• Complete route release (including overlaps, if any) should be activated efficiently.
• Route release should be sequential, following signal 'ON' status and operated button/switch.
• Separate circuits exist for the release of individual route sections.
• Sectional route release is implemented for installations with more than a hundred routes. Provisions are made for the automatic release of a route following the authorized passage of a train.
• There are specifications for delays in route release during emergency situations based on the type of approach track occupancy.

Section 6 and 7

• Maintenance and specifications for installation, testing, and maintenance of electronic interlocking.
• Surge and lightning protection for related electrical and electronic equipment is included.
• Earthing specifications for the equipment are included.

Relay Interlocking:

• Relays and relay racks, including their connection and configuration.
• Specific safety characteristics for connections required.
• Installation, maintenance, and periodic/general maintenance requirements and standards.