Signalling in 25 KV AC Electrified Areas

Voltage created in conductors due to factors like the length of parallelism with electrified tracks and soil conductivity.

The ability of a train driver to see a signal.

Technical drawings demonstrating the allowed and disallowed areas for signal posts based on track types (tangent, curves with different elevations).

The standard size limits of signal posts for safety.

Railway sections with overhead electrical systems.

Installation and positioning of signal posts, observing clearances.

A group that checks the visibility of signals to ensure safe train operation.

Protecting cable sheaths from influencing electric fields to minimize induced voltage.

Signalling equipment must function correctly even with traction current and in faulty conditions, preventing false signals and ensuring train safety.

Visibility of signals, electrical clearances from overhead lines, traction return current, and electromagnetic induction.

OHE structures must be designed to maximize signal visibility.

Signals must have enough space from live overhead lines to avoid electrical issues.

Minimized by using underground cables to insulate circuits from outside electrical fields.

Causes voltage variations in parallel conductors like rails, return conductors, cable sheaths, and signalling circuits.

Used to maintain safe electrical distances when signals are too close to live OHE for wires.

Electrical connections for overhead lines that are needed for proper operation of Signal & Telecommunication (S&T) equipment.

Diagrams 22-D1, 22-D2, and 22-D3 show clearances for double-wired catenary systems, excluding anchor spans, turnouts, areas 3 meters from masts, and loco sheds/inspection pits; also excluded are areas with feeder lines near masts, boosters, and return conductors.

Typically 5.60 meters above supports for broad gauge.

Usually 7.05 meters at the highest point for broad gauge.

In tunnels and under bridges, clearances can be reduced to 4.58 meters for the contact wire; the catenary is lowered or terminated accordingly.

No one should approach live overhead line parts (O.H.E) closer than 2 meters.

Signal posts within 2 meters of live conductors must have iron screening, or caution boards, if screening is not feasible.

Protective measures are taken when signalling staff work near 25 kV live conductors. This is done by constructing or providing safety screens or signage indicating caution.

If iron screening is not possible, a caution board must be placed 3 meters above rail level on signal posts.

Tools and equipment must remain at least 2 meters away from live electrical equipment and return conductors, which are considered live.

Signal locations (22-D4/22-D5) on Broad Gauge tracks need specific minimum heights and distances from the track to prevent electrical interference.

Neutral sections should be placed away from stop signals, level crossings, and preferably on tangent tracks, to ensure train safety and prevent stalling.

The distance between a neutral section and stop signals varies depending on gradient. 1600 meters for up to 1 in 300 gradient, and 2500 meters for steeper gradients up to 1 in 200. Distance must ensure sufficient train speed before or after signal.

PTFE-type short neutral sections should be positioned 400 meters after or 200 meters before the stop signal on level tangent tracks.

If complying with neutral section guidelines is difficult/expensive, the Chief Electrical Engineer can authorize alternative arrangements that are safe and reliable, but must comply with gradient rules.

SSE/JE (Signal) personnel must instruct staff on safety procedures around live equipment and ensure their compliance with safety rules.

Electrical engineers prioritize safety when locating signals and neutral sections, considering factors like train speed and track conditions.

Signals are typically placed on the left side of the track they control. In special cases, they may be on the right.

Signals must be clearly visible, so extra care is taken to avoid obstructions like traction masts and structures.

Spacing of traction masts around signals follows strict rules to ensure good visibility.

Signal posts must be tall enough to be seen easily.

Signals on curves or near obstructions need special attention to ensure good visibility.

Signal posts and fittings must be positioned within defined limits to avoid interfering with the track.

Special signals that show the direction a departing train will take.

The center line of a red signal must be approximately 3.65 meters above rail level, and the entire signal (without a route indicator) should not exceed 5.2 meters.

Signals located between tracks require a clear space of at least 600 meters behind them for OHE structures and portal drop arms.

If a portal drop arm is unavoidable near a signal, the signal must be mounted on an offset bracket. Extra study is also needed for the drop arm placement.

If the signal's visibility is inadequate, speed restrictions may be imposed, and actions must be taken to re-establish a clear line of sight.

Signalling equipment needs to operate flawlessly despite the presence of traction current and potential faults to ensure safe train operations.

Special clearance regulations apply for signals in areas with high-rise overhead equipment (for double-stack containers or three-tier cars).