Signalling in 25 KV AC Electrified Areas
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Questions and Answers

Signalling equipment must function normally despite the presence of traction current.

True

No traction mast should be located less than 5 meters in advance of the signal post.

False

Electrostatic induction is completely eliminated when using overhead electified (OHE) structures.

False

The height of the centre line of the red signal should be approximately 3.65 meters above rail level.

<p>True</p> Signup and view all the answers

Visibility of signals in AC electrified areas is solely dependent on the surrounding environment.

<p>False</p> Signup and view all the answers

Return current through rails and conductors can influence induced voltage levels.

<p>True</p> Signup and view all the answers

Signals located between tracks can have OHE structures provided in the same track space within 600 meters in rear of the signals.

<p>False</p> Signup and view all the answers

Only traditional incandescent signals shall be utilized in electrified areas.

<p>False</p> Signup and view all the answers

Portal drop arms are allowed to be located within 600 meters before the signal as long as they do not infringe with the track schedule.

<p>False</p> Signup and view all the answers

The signal post should be lower than the OHE mast when positioned on tangent tracks.

<p>False</p> Signup and view all the answers

Electrical clearances of signals in electrified areas should always be maintained without provision for protective measures.

<p>False</p> Signup and view all the answers

The site for signals on curved tracks should be examined individually by a committee.

<p>True</p> Signup and view all the answers

Electro-magnetic induction causes varying currents and voltages in conductors parallel to the track.

<p>True</p> Signup and view all the answers

The length of parallelism between cable conductors and electrified track has no effect on induced voltage.

<p>False</p> Signup and view all the answers

The maximum height for a signal without a route indicator is 6.0 meters above rail level.

<p>False</p> Signup and view all the answers

Special studies must be conducted if a portal drop arm is located in rear of the signal itself.

<p>True</p> Signup and view all the answers

The maximum permissible induced voltage for human safety is restricted to 600 V.

<p>False</p> Signup and view all the answers

The maximum length of direct feed of signal on a single track using unscreened cable is 180 m.

<p>True</p> Signup and view all the answers

Double track systems using unscreened cable can have a maximum length of 250 m.

<p>False</p> Signup and view all the answers

Controlling relays must be located at the site when a signal exceeds the prescribed distance.

<p>True</p> Signup and view all the answers

Signal feed systems must operate at 60 Hz to align with regulations.

<p>False</p> Signup and view all the answers

The value of the factor of safety considered for the maximum permissible induced voltage is 2.0.

<p>False</p> Signup and view all the answers

The purpose of limiting the distance between signal control relays and the signal is to prevent illumination of lamps under adverse conditions.

<p>True</p> Signup and view all the answers

All relay types listed can withstand an induced voltage below the maximum permissible limit.

<p>True</p> Signup and view all the answers

If the distance between two insulators on the same rod exceeds 300 meters, additional insulators are not required.

<p>False</p> Signup and view all the answers

The operating rod of locally worked points must have an insulator to ensure insulation from the rail.

<p>True</p> Signup and view all the answers

The clearance between the insulator and the adjacent rod roller may be minimal and does not need to permit movement.

<p>False</p> Signup and view all the answers

When a rod crosses the track, it must maintain a minimum height of 40 mm from the bottom of the rail.

<p>True</p> Signup and view all the answers

All insulators in a run can be provided between different sets of rollers and guides.

<p>False</p> Signup and view all the answers

Railway personnel do not need to take precautions when working near 25 KV A.C traction.

<p>False</p> Signup and view all the answers

The distance between any overhead equipment mast and the point rods should be at least 40 mm.

<p>True</p> Signup and view all the answers

Presence of return currents in the rails poses no risk to railway personnel.

<p>False</p> Signup and view all the answers

The staff responsible for the operation of the Signalling equipment must check whether all signalling equipment is functioning normally.

<p>True</p> Signup and view all the answers

If any equipment is found to be functioning abnormally, its operation can continue without immediate suspension.

<p>False</p> Signup and view all the answers

An authorized representative must submit a Certificate after ensuring that everything is working correctly.

<p>True</p> Signup and view all the answers

The checklist for works to be completed is issued by the Chief Engineer of the Signal and Telecom department.

<p>False</p> Signup and view all the answers

Existing DC track relays must be replaced with AC immunized relays as part of the anti-theft measures.

<p>True</p> Signup and view all the answers

A clearance certificate from DOT is not necessary prior to the 2.2 KV anti-theft energisation.

<p>False</p> Signup and view all the answers

The working clearance needed for signalling installations should be at least 2 meters from any live conductor.

<p>True</p> Signup and view all the answers

Insulated tools must be provided to maintenance staff for safety during their work.

<p>True</p> Signup and view all the answers

The minimum height for masts before a signal without approach should be 3.25 m for distances beyond 400 m.

<p>False</p> Signup and view all the answers

Masts should ideally be placed in the same lane as signals for at least 600 m before a signal when signals do not have route indicators.

<p>False</p> Signup and view all the answers

The minimum setting of masts for colour light signals with horizontal route indicators varies based on distance ranges up to 310 m.

<p>True</p> Signup and view all the answers

The height of masts for signals other than distant signals starts at 3.25 m.

<p>True</p> Signup and view all the answers

For colour light signals without route indicators, the minimum setting of masts remains constant regardless of distance.

<p>False</p> Signup and view all the answers

Masts before signals with horizontal route indicators should have a minimum height of 2.75 m for distances up to 250 m.

<p>False</p> Signup and view all the answers

When setting masts for colour light signals with route indicators, at least five different height settings are specified.

<p>True</p> Signup and view all the answers

The minimum height of masts for colour light signals located between tracks should always be 3.25 m.

<p>False</p> Signup and view all the answers

Study Notes

Signalling Requirements in 25 KV AC Electrified Areas

  • Objectives: Ensure signalling equipment functions normally in the presence of traction current, prevent interference from traction systems that could imperil train safety, and protect personnel from electric shock.

Factors Affecting Signalling

  • Visibility: Proper OHE (Overhead Line Equipment) placement during design is crucial for signal visibility. Protective shields are necessary where electrical clearances can't be maintained. Signal layout plans must align with approved signalling plans. Protective wire-mesh screens are required in situations where clearances from live OHE conductors are more than 2 meters

  • Electrical Clearances: Electrical clearances of signals are needed because of live overhead line equipment.

  • Traction Return Current: This current can affect signal operation.

  • Electrostatic/Electromagnetic Induction: These factors influence signals by inducing currents and voltages in parallel conductors. Various factors like conductor parallelism, soil conductivity, cable screening, return current paths, mutual inductances, and current carried by the catenary affect the voltage.

Signal Structures in Electrified Areas

  • Colour Light Signals: Only colour light signals are used in electrified areas.

  • Signal Clearance Diagrams: Specific diagrams (Drg. No 22-D1, etc.) guide signal location and clearance from live parts of OHE based on tangent and curved track configurations with specific super-elevation values.

  • Signal Visibility: Signal locations must ensure visibility for train operators (Loco pilots). Signal sighting committees should verify visibility and make necessary adjustments.

Signal Circuits

  • Aerial Circuits: Avoid using aerial signalling circuits within electrified zones.

  • Earth Returns: Avoid using earth-return circuits in AC electrified areas.

  • Equipment Protection: Electrical signalling equipment that cannot safely withstand AC induced voltage should be used within designated locations, like cabin or internal circuit boxes,and have no external connections. Batteries and wire connections for such equipment must be well insulated from ground.

  • Relay Response (Interlocking): Relays that release interlocking should have a delay (0.6-0.8 seconds) to prevent inadvertent release from voltage fluctuations.

Outdoor Signalling Circuits

  • Parallelism: Maintain circuit lengths that ensure induced voltages from traction systems don't exceed 400 Volts. Sectionalization of line circuits may be required in some cases. Power supply is needed to prevent voltage limits

  • DC Circuits: Length limitations exist for DC circuits based on the type of relay, immunity level, and whether cables are screened.

  • Signal Feeding: Signal feed system should be 110V/50Hz. Maximum length for direct signal feeding is important and is determined in a table.

Point Operation

  • Electric/Mechanical Operation: Point operation might be electric or mechanical. Precautions are required when engaging the mechanism that operates points.

  • Length Restriction & Immunity: The length of electric point operation is restricted based on point machine type and immunity level.

Insulated Rod Joints

  • Insulators: Rod joints should have insulation provided in the lead-out portion, particularly close to the cabin, to prevent transmission of rail voltage and other hazards. Additional insulators are needed between certain sections, or if the distance is greater than 300 meters. Isolated points from tracks are essential.

  • Clearances: Maintained clearances between rail, insulators, rods, and other equipment parts are crucial to avoid electric shocks.

Staff Protection

  • Proximity to Live Conductors: Avoid contact with live conductors (25KV).

  • Return Current: Return currents in rails can create potential differences that are potentially hazardous, and require careful handling and attention.

  • Insulated Tools and Materials: Workers need to use insulated tools and materials for safety during maintenance/repair.

  • Safety Precautions: Specific procedures/rules apply when working on signalling equipment in electrified areas to protect workers from electric shock or other hazards.

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Description

This quiz explores the signaling requirements in electrified areas with 25 KV AC traction systems. Key aspects include ensuring safe operation of signaling equipment, preventing interference from traction systems, and understanding the factors affecting visibility and electrical clearances. Test your knowledge on these crucial topics for train safety.

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