CH 22 Section 4-7 Signaling Circuits PDF

Section 4: Signaling Circuits in RE area 22.4.1 As a rule, no aerial circuits shall be retained in the electrified zone. In every case, the length of parallelism and the distance of Block Wires from the nearest electrified track shall be checked to ensure that the maximum induced...

Section 4: Signaling Circuits in RE area 22.4.1 As a rule, no aerial circuits shall be retained in the electrified zone. In every case, the length of parallelism and the distance of Block Wires from the nearest electrified track shall be checked to ensure that the maximum induced voltage does not the exceed 60 volts limits prescribed by CCITT. 22.4.2 Barring block-instrument circuits, no other earth-return circuit shall be permitted in A.C electrified territory. Block instruments, however, shall be suitably protected by a filter of approved design as explained in Chapter 18 of SEM. 22.4.3 The following electrical signalling equipment are not safe to withstand AC induced voltage. The coils of this equipment can only be used inside a cabin or a location box or internal circuits only. The coils of these equipment shall be worked from a separate battery/DC-DC Converter and this battery/DC-DC Converter shall not be connected to any external circuits going outside the cabin/location box. (a) Luminous Indicators. (b) Telephone type relays. (c) Electrical Lever Locks. (d) Door Coil of IRS Block Instrument. (e) 250 Ohm D.C. neutral Line Relay. (f) Rotary Key Transmitter. (g) D.C. Neutral Polar Relays. 22.4.4 All Batteries and the wiring in the equipment, location box or cabin shall be well insulated from the ground. PVC insulated wires to an approved specification (IRS- S-76) shall be used for wiring in location boxes and cabins. 22.4.5 Separate Batteries/DC-DC Converters shall be provided for external and internal circuits. 22.4.6 When more than one cable is laid between two locations or cabins, it shall be ensured that as far as possible, all wires pertaining to any individual circuit are within the same cable. 22.4.7 Polarized Relays using permanent magnet shall not be used in any external circuit in 25 KV AC electrified areas as the permanent magnet in the relay tends to lose its magnetic properties due to continuous application of induced voltages. Competent authority shall authorise any exception in specific cases. 22.4.8 The relays, which release an interlocking, shall be slow acting so that the interlocking is not released inadvertently by voltage variations of short duration. Time delay may be of the order of 0.6 to 0.8 seconds. 22.4.9 All external circuits in AC. electrified area shall work with double cutting. Chapter 22: Requirements Of Signalling In 25 KV AC Electrified Area Page 479 of 530  Section 5: Outdoor Signalling Circuits in RE area 22.5.1 Maximum Length of Parallelism (a) The length of any signalling line circuit must be limited to ensure that the induced voltage from the traction system does not exceed 400 Volts under normal conditions. If necessary, line circuits must be sectionalized. Where line circuits leave line side enclosures or buildings in different directions, this could give rise to a continuous circuit of such length that the limits of induced voltage above could be exceeded. In such cases a sectionalized power supply unit should be provided for each direction. (b) The induced voltage in the underground-Unscreened cable shall be reckoned as 116 Volts/km on single line and 95 Volts/km on Double Line under normal conditions when the catenary current of 800 amperes for single line and 1000 amperes for double line. (c) When such circuits are terminated on relays/equipment their immunity shall not be less than 400 V AC. Length of feed cable terminated on relay shall be suitably reduced depending upon its AC immunity. (d) The length of DC Circuits on Line Relays with unscreened cable shall be restricted to- Type of Relay AC immunity Maximum permissible length on* level in volts Single Line Double Line QNA1/QNNA1/QNA1K 1000 2.1 km 2.8 km K50 B1 170 1.0 km 1.2 km K50 B1-A2 450 2.1 km 2.8 km K50 130 750 meters 900 meters AC Immunized neutral 750 2.1 km 2.8 km relay (IHC Make) * Maximum permissible induced voltage is restricted to 400 V for human safety and factor of safety 1.5 has been considered. Section 6: Signal Feed Circuitry in RE area 22.6.1 Feeding Distance Signal feed system shall be of the 110 V 50 Hz type or any approved type. 22.6.2 The distance between the signal control relays and the signal must not exceed the prescribed limits in electrified zone, measured along the line of way. This will ensure that the voltage induced in the circuit will be inadequate to illuminate the lamps, even under the most adverse circumstances and with one or more earth faults present. Chapter 22: Requirements Of Signalling In 25 KV AC Electrified Area Page 480 of 530 22.6.3 Maximum permitted length of direct feed of signal shall be as per Table given below. Type of Cable 110 Volts feed system Single Track Double Track Unscreened 180 m 220 m 22.6.4 When a signal is located at a distance greater than that specified in para 22.6.3 the signal shall be fed locally by controlling relays located at the location. Such signals may also be remotely fed from the cabin by using a controlling relay at the location. Typical circuit is given in Drg. No. 22-D9. 22.6.5 It shall be ensured that the power transformer for feeding circuits as per para 22.6.2 shall be different from the transformer feeding longer circuits. Section 7: Point Operation & Detection in RE area 22.7.1 Point can be operated electrically or mechanically by rodding. Mechanical operation of point will require special measures for the protection of operating staff. Electric operation shall have restriction on maximum length between point control relays and point machine depending upon their immunity level. 22.7.2 Electric Operation of Point (a) Point detection and point detection repeat circuits shall use ac-immunized relay. (b) The maximum permissible length for various types of commonly used Point Machines is as under: Maximum permissible parallelism in meters Type of AC immunity between Point Contactor and Point Motor Machine level in volts Single line Double line As per 160 910 1100 IRS S-24 400 2200 2800 Factor of safety is 1.5 (c) 3 phase point machine is inherently immune to induced voltage and therefore can be used for operating point to any length subject to its own operating limitation. Chapter 22: Requirements Of Signalling In 25 KV AC Electrified Area Page 481 of 530 22.7.3 Rod Runs in RE Areas The point rods in A.C electrified areas are subject to a certain amount of induced voltage. In addition since the rods are in contact with the rails at some point or other, the rail voltage, which can be quite high in case of faults, is transmitted through them to the lever frame. Insulators shall, therefore, be provided on the rodding as per instructions in para 22.7.4 for protecting the Operating & Maintenance Staff from the effects of these voltages. 22.7.4 Insulated Rod Joints for RE (a) The insulated rod joints shall be as per approved drawings. (b) Each rod shall be provided with an insulator in the lead out as close to the cabin as possible. While providing this insulator, it shall be ensured that there is no possibility of a contact between the insulated portion of one rod and the un-insulated portion of another rod or signal wires, the rail or O.H.E mast. (c) An additional insulator shall be provided between the last adjustable crank and the point or the lock bar. The purpose of this insulator is to prevent the rail voltage being passed on to the main run of rods. (d) If the distance between the two insulators at either end is greater than 300 meters, additional insulators shall be provided on each rod, so that the distance between two consecutive insulators on the same rod is not greater than 300 meters. (e) Each Point, Trap indicator and lock bar operated by rodding shall be electrically isolated from the track. (f) All insulators in a run shall be provided between the same two sets of rollers and guides, so that there is no possibility of the insulated portion of one rod coming into contact with the un-insulated portion of another rod. (g) The clearance between the insulator and the adjacent rod roller shall be adequate to permit normal movement of the rod. (h) When a rod crosses the track, the top of the rod shall not be less than 40 mm from the bottom of the rail. When steel or C.I sleepers are used, the distance between the rod and the sleeper shall be also not less than 40 mm. Similarly, the distance between any O.H.E mast and the point rods shall not be less than 40 mm. (i) The operating rod of locally worked points on all electrified lines and of similar points taking off from the non-electrified track adjacent to the last electrified line shall also be provided with an insulator so that the point lever or point box is insulated from the rail. (j) When the Engineering department provides the point lever or point box, Engineering department shall provide the insulator on the operating rod. Chapter 22: Requirements Of Signalling In 25 KV AC Electrified Area Page 482 of 530