Railway Electrification Principles

If clearance isn't achieved, use earthed metallic screens or warning boards.

A conductor that carries current from the tracks to a substation in a booster transformer system.

Based on IS: 875-1964 (updated 1971). Wind pressure varies by zone (Green, Yellow, Red).

A device that keeps the tension of overhead line conductors constant, regardless of temperature changes.

The horizontal distance between the traction mast and the center of the track.

Green (light), Yellow (medium), Red (heavy) zones determine wind pressure values.

The horizontal distance from the catenary's suspension point to the mast.

Consider projected area of rolled sections (150%), fabricated structures (150%), and conductors/circular members (2/3rd).

Checked under two conditions: (a) 35°C, full wind pressure; (b) 4°C, 20% governing wind pressure.

The distance between supporting masts for overhead equipment.

Use steel tape. On curves: outer rail (odd tracks), inner rail (even tracks). On single tracks: outer rail.

The horizontal distance of the contact wire from the vertical plane through the pantograph's center.

Use documents (Drg. Nos.) for conventional, regulated tramway, and composite OHE.

The horizontal distance of the catenary suspension bracket from the vertical plane through the track.

A device in the contact wire that electrically isolates sections while allowing continuous pantograph contact.

Maximize span length while maintaining permissible stagger. Consider curvature, equipment blow-off, sway (pantograph), mast deflection.

A general term for outdoor equipment controlling power delivery to overhead equipment.

A supply post where 25 kV feeder lines from a substation connect to the overhead equipment.

A supply post mid-way between two feeding posts for switching and combining power.

A supply post with a sectioning and paralleling interruptor.

A supply post with a sectioning interruptor, for single line sections.

Choosing the appropriate mast type for overhead line equipment (OHE) based on wind pressure, OHE type (conventional or composite), and specific location characteristics.

Documents specifying which mast types are suitable for different OHE applications and wind pressure zones.

Overhead line equipment with a specific catenary and contact wire configuration.

OHE that uses an aluminum alloy catenary.

Categories defined by wind force, which determine the appropriate mast strength.

A type of mast that can be substituted for K-series masts.

The location of the mast's placement.

Predetermined distances used for standard mast placements.

Bridges exceeding 150m in length.

Maximum bending force the mast can withstand without structural failure.

OHE masts should not be placed in front of station entrances.

Avoid placing masts opposite trolley refuges, near culverts, subways, and bridges shorter than 50m.

OHE masts must be situated at least 10 meters beyond a signal post; or 30 meters if in front of a signal post.

Masts should be placed far enough from level crossings and the back of bridge abutments; usually at least 10m away.

Sections with more than two tracks need independent masts if track centres are good or tracks can be moved; otherwise, portals are used.

When conditions are not ideal, prefer the side with better stability for placing masts.

In tunnels, OHE cantilever support stubs should be provided on both sides; for restoration if one side is damaged.

Bridge masts need core holes on both sides of all piers (as per document RE/31/0590/63) for proper erection; fill unused holes with sand and concrete slab.

Special precautions are needed for wiring on petroleum sidings (as per given documents).

Overhead equipment is supported from masts using bracket assemblies, which are typically swiveling for adjustment.

Cantilever arrangements depend on factors such as contact wire height, obstacles, distances, and track design.

Platform cantilever arrangement follows guidelines from Documents ETI/.OHE/G/-2104, Sheet 2.

A bracket assembly of a special design, used on bridges and tunnels, after a clearance study.

Bracket assemblies are designed for suspension distances up to 3.5 meters. If the distance is more, the bracket chair from drawing numbers ETI/OHE/P/3050 and RE/33/P/3100 must be used.

In environments like tunnels, coastal areas, or near industrial facilities (chemical, fertilizer, cement plants, steam loco sheds, etc.), long creepage path (1050mm) insulators are used on cantilever assemblies.

Standard mast setting is 2.50 meters from the tangent track centerline. It can be reduced to a minimum of 2.36 meters in special cases (yards, cuttings, bridges) with Chief Electrical Engineer's approval.

Standard mast setting is 2.35 meters from the tangent track centerline. It can be reduced to a minimum of 2.14 meters in special cases with Chief Electrical Engineer's approval.

For portal uprights, masts carrying more than one overhead line equipment (OHE), and head span masts, the setting should normally be less than 3.00 meters (broad gauge) and 2.50 meters (meter gauge).

Curve mast setting is determined by adding curve allowance and 150 mm slewing allowance to the tangent track setting (para 20.1). Different allowances apply for different routes based on speed potential.

For broad gauge main lines on outside curves, the standard setting is 2.50 meters for radii greater than or equal to 875 meters and 2.65 meters for radii less than 875 meters.

A conductor that carries current from the tracks to the substation in the booster transformer system.

A device that maintains constant overhead line conductor tension despite temperature changes.

The horizontal distance from the traction mast's face to the track's center line.

The horizontal distance from the catenary suspension bracket's eye center to the mast's face.

The distance between adjacent supporting masts for overhead equipment.

The horizontal distance of the contact wire from the vertical plane through the pantograph's center.

A device within a contact wire that electrically isolates sections, enabling continuous pantograph contact.

A general term for outdoor equipment controlling power supply to overhead equipment.

A supply post where 25 kV feeder lines from the substation connect to the OHE.

A supply post positioned mid-way between feeding posts, enabling switching and combining power.

Categories (Green, Yellow, Red) defining wind strength for design, influencing load calculation.

Calculating wind load involves considering projected areas of various components (rolled sections, fabricated structures, conductors).

Safety of masts and portals is assessed under two temperature and pressure conditions for design.

Precisely measuring the distance between supporting masts, using a steel tape or other tools.

Using specified drawings (e.g., ETI/OHE/G/00202) for different overhead line equipment types.

Maintaining maximum span length while meeting limits on stagger, ensuring overhead equipment remains stable and functional.

For areas where clearances can't meet standards, use earthed metallic screens or warning signs.

Structural design based on IS: 875-1964 (and 1971 amendment).

The preferred spacing of overhead equipment under over-line structures, measured in meters.

Table showing preferred spacing values based on span length under over-line structure, in meters.

Distance between overhead equipment supports (masts).

Maximum allowable span length for adjacent spans.

A structure that is positioned over an existing overhead line.

Table showing recommended spacing values for various span lengths.

When encumbrance cannot be increased from the recommended value to 1.40 meters in a single span.

Carries current back to the substation from the tracks in a booster transformer system.

Run as close as possible to overhead equipment for maximum compensation.

Must maintain a minimum 400mm clearance from overhead equipment, accounting for worst-case scenarios.

A minimum 150mm distance from earthed structures for steady-state conditions.

Requires 80mm of distance from an earthed structure to accommodate movement.

Run straight through over bridges if possible, maintaining standard clearances and avoiding platform obstructions.

In areas with complex tracks, the return conductor placement is based on individual case studies.

Typically connected to masts where they are linked to the rail, sometimes anchored back-to-back.

At booster stations, use cut-in insulators for each track, with connections to booster transformers per drawings.

Midpoint of return conductor should be connected to a buried rail adjacent to booster transformers or feeding posts, following RDSO drawings.

When the midpoint of a section isn't near feeding or sectioning posts, two rail links must be placed in front of feeding and sectioning posts on either side of an insulated area. The midpoint is not connected in these cases.

A 10 kVA single-phase transformer providing 230 V power to substation equipment, yard lighting, and signals.

10 kVA, but multiple transformers may be used for larger stations or yards.

Protected by a 25 kV dropout fuse on the primary side and a 63 A rewireable DC fuse on the secondary side.

Mounted on a steel platform on the OHE mast, connected to the 25 kV OHE using aluminum bus-bars or copper jumpers.

A 100 kVA, 25 kV/230 V transformer used in substations for single-phase oil centrifuging/filtration.

Traction masts are connected to non-track-circuited rails, particularly portals (one upright) and head spans (both masts).

Rail bonds connect running rails across rail joints.

Connect rails of the same or adjacent tracks.