Electrical Signaling Circuits Testing and Inspection

Testing Instruments

• Suitable instruments like Multi-meter, Volt meter, Ammeter, Ohmmeter, Frequency meter, Bell tester, Earth Tester, Earth leakage detector, Cable fault locator, Cable route tracer, Relay contact testing/cleaning kit, etc. should be used in the testing of electrical signalling circuits.
• Calibration of these instruments should be checked periodically.

Physical Inspection of the Installation

• Check that the work has been carried out in accordance with the approved plans and that equipment is of proper type and in good condition.
• Check the following aspects during site inspections:
  • Signals, location boxes and other outdoor equipment are as per approved plans and in good condition.
  • Arrangements for proper ventilation, where provided, are not choked.
  • Each location contains all the apparatus required as per approved plans, and the apparatus is of approved type.
  • The location of insulation joint, jumper wiring, traction bonding in electrified areas, point machines, switch locks, and other apparatus is as per approved plans and their condition is satisfactory.
  • The electrolyte, inter-connections between cells, cell voltage, etc. are in the required condition as per relevant specifications or instructions.
  • Each wire is tagged or marked where feasible so that it can be identified at each end, and the nomenclature on the tag corresponds to that on the wiring diagram.

Earthing

• Earthing shall be provided at the lever frame and other metallic frames of the cabin.
• Earthing shall be provided at every location box where cables terminate.
• Earthing shall be provided at each signal.
• Wherever possible, the common earthing system shall be provided for closely located location boxes, signal posts, etc.
• Separate earth is required for equipment requiring functional earth only.
• Sheath & Armour of Main cables to be earthed. Armour of OFC shall be earthed at both ends.
• In case of signals falling within 2 meters from the electrified track, the protection screen shall be connected to an earth.
• There shall not be any possibility of simultaneous human contact with metallic bodies connected to different earths, where it is not possible to provide suitable spacing or partition between various metallic objects referred to above, they shall be connected to a common earth.
• Common/Equi-potential earth for modern electronic equipment such as EI, DAC, Datalogger, etc. to be used in Relay room. Earth value shall not be more than one ohm and shall be measured annually during dry season.

Power Supply Arrangements

• Power supply systems for Signalling Installations shall be as per Chapter 16.

System Integrity Testing (SIT)

• System Integrity Testing (SIT) is a complete testing involving both Indoor & Outdoor signalling equipment for functional working & safety to be done in a new installation, at every interlocking alteration or periodically once in five years.
• The signalling installation as a whole must be tested with detailed operational, functional and safety tests as per approved Control Table/Route Chart and Signalling & Interlocking Plan.

Precautions during Testing

• Following precautions shall be taken during testing and checking so that:
  • No signal taken 'OFF' for a train movement is thrown to 'ON' in the face of the train.
  • No signal which will create a conflicting or unsafe movement is taken ‘OFF’.
  • No point and isolation in a route set for a train movement is disturbed.
  • No track relay of an occupied track circuit is energised.
  • No voltage higher than permissible levels is applied to the equipment.
  • There should be no risk of electric shock to testing or operating personnel.

Maintenance of Outdoor Signalling

• Insulation tests on Cables shall be done as per Chapter 15 of SEM.
• Cleanliness of LED Lenses: Polycarbonate Lenses of LED lamp shall be kept clean, and housing shall be kept clean and opening in inclement or stormy weather avoided.
• Replacement of Defective LED lamps must be immediate, and new lamp shall be pre-tested as per approved instructions before putting into use.

Earthing for Outdoor Signalling Equipment

• Earths are of two types: Functional Earth and Protective Earth.
• Perimeter Ring Earth (PRE) shall be provided around building housing signalling equipment.
• Chasis of all S&T equipment shall be bonded to BRC (Bonding Ring Conductor) provided inside the Power Equipment Room or Signal Equipment Room.
• Earthing shall be provided as per approved specifications, drawings and code of practice issued by RDSO.
• The maximum earth resistance shall be specified as per OEM & RDSO recommendations.
• Earthing of cables, equipment, buildings, and structures is done for one or more of the following purposes: Lightning & surge protection of equipment, Earthing of metal screens of telecommunications cables and equipment for reducing Electromagnetic interference, and Human safety.

Installation of Signalling Equipment

• Imperfect joints in soldering can be caused by a soldering iron that is not hot enough, not holding the iron on the connection for long enough, unclean terminals or wires, or using solder with an improper composition or fluxing agent.
• Newly soldered connections should not be disturbed until the solder has cooled.

Wire Termination

• When terminating wires, care should be taken to bend the wires in a clockwise direction.
• Wire strippers should be used, and cutting pliers should not be used.
• Washers and check nuts should be used when fastening.
• No more than two wires should be terminated on one terminal.
• Multi-strand wires should be terminated on terminal lugs and covered with insulation sleeves.
• Crimping tools of appropriate design should be used, and proper soldering should be ensured.

Installation of Colour Light Signals

• Colour Light Signals should be multi-unit and equipped with LED lamps.
• The location and spacing of signals should be in accordance with approved plans and codal provisions.
• The signal should be located to provide a clear view to the Loco pilot of an approaching train and should be as close to the track as possible.
• The signal should have a minimum visibility as indicated in para 7.1.11.

Point Machines and Notches

• Electric Point Machines should be provided with suitable gaskets, and wire entrances should be sealed to make them water-tight and dust-proof.
• All extra openings should be closed as far as possible.
• Locking: Electric Point Machine covers should be locked, and the cover provided for insertion of crank handle should also be locked with a separate key.
• Notches in Stretcher Blades should not be tampered with or reconditioned. Worn-out slides should be replaced with new ones.

Testing of Relay Interlocking

• Testing of Relay Interlocking involves operating point No. 2 to reverse position and clearing the signal route No. 2WBI by operating the signal switch/button.
• The point should remain locked, and then the point knob should be restored to reverse.
• De-energise 2RWKR, and signal 2WBI should go to 'ON'.
• Restore the signal switch/button to normal, and when point No. 2 is free, shunt the track 2T.
• Turn the point knob 2 from reverse to normal, and the point should remain locked.

Lubrication and Maintenance

• All gearing and bearings should be properly lubricated according to manufacturer's instructions.
• Commutators should be kept clean, smooth, and have a bright appearance.
• Brushes should be kept clean and properly bedded on the commutator.
• All cables and connections should be checked for intactness.
• Adjustment of Contacts should be clean, free from pitting, and in proper adjustment.
• Rain water drainage arrangements should be checked, especially prior to and during rainy season.
• Fixing nuts and screws of newly installed point machine often tend to get loose, and care should be taken to attend to them and readjust where required.

Testing of Point Machine

• Each sectional JE/SSE (signal) should test the point machine and do adjustments of the machine by conducting obstruction test as per para 19.3.6 & Annexure 19-MS2.

Maintenance of Electrical Point Detector (EPD)

• Maintenance schedule as shown in Annexure: 19-MS3 should be followed.

Earthing for Outdoor Signalling Equipment

• There are two types of earths: Functional Earth and Protective Earth.
• Perimeter Ring Earth (PRE) should be provided around the building housing signalling equipment.
• Chasis of all S&T equipment should be bonded to BRC (Bonding Ring Conductor) provided inside the Power Equipment Room or Signal Equipment Room.
• Earthing should be provided as per approved specifications, drawings, and code of practice issued by RDSO.
• The maximum earth resistance should be specified as per OEM & RDSO recommendations.
• Earthing of cables, equipment, buildings, and structures is done for one or more of the following purposes: Lightning & surge protection of equipment, Earthing of metal screens of telecommunications cables and equipment for reducing Electromagnetic interference, and Human safety.