Electric Railway Systems Overview
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Questions and Answers

What is the main purpose of a neutral section in overhead equipment?

  • To provide a resting area for electric trains
  • To separate the areas fed by adjacent substations (correct)
  • To allow locomotives to pause and recharge
  • To increase voltage supply to the overhead equipment

    • Why are warning boards provided in advance of a neutral section?

  • To alert passengers about upcoming stops
  • To indicate a change in train speed limits
  • To signal the end of a feeding post
  • To remind the loco pilot to open the circuit breaker (correct)

    • How many interrupters are typically provided at each Sub-Sectioning Post (SSP) in a double track section?

  • Three (correct)
  • Two
  • Four
  • One

    • What equipment is installed at switching stations to protect against voltage surges?

    <p>Lightning arresters</p> Signup and view all the answers

    What should a train do when approaching a neutral section?

    <p>Coast through it without stopping</p> Signup and view all the answers

    What is the function of Auxiliary transformers at switching stations?

    <p>To supply ac at 240 V, 50 Hz for essential systems</p> Signup and view all the answers

    Where should neutral sections be located for optimal operation?

    <p>On level tangent tracks, away from signals and crossing gates</p> Signup and view all the answers

    Which of the following provides monitoring for power supply to sub-sectors?

    <p>Potential transformers</p> Signup and view all the answers

    What does the first letter in the code for electric locomotives denote?

    <p>The gauge</p> Signup and view all the answers

    Which letter is used to denote locomotives suitable for mixed traffic services?

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

    What type of pantograph is commonly used by Indian Railways for electric locomotives?

    <p>AM 12</p> Signup and view all the answers

    What is the maximum operational speed suitable for the pantograph described in the content?

    <p>140 km/h</p> Signup and view all the answers

    What is the typical equivalent copper section for catenary and contact wires together?

    <p>157 mm2</p> Signup and view all the answers

    Which code letter represents locomotives meant exclusively for freight services?

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

    Which equipment is used for collecting power from overhead contact wires in electric locomotives?

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

    What is the maximum permissible current on a single track due to the size of the overhead equipment?

    <p>600 A</p> Signup and view all the answers

    What is the normal height of the contact wire for regulated overhead equipment above rail level?

    <p>5.60 m</p> Signup and view all the answers

    What technology is used to raise and lower the pantograph?

    <p>Pneumatic servo motor</p> Signup and view all the answers

    For unregulated overhead equipment in areas with a temperature range of 4°C to 65°C, what is the height of the contact wire?

    <p>5.75 m</p> Signup and view all the answers

    What classification is given to electric multiple units (EMUs)?

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

    Which of the following pantograph features improves operational speed potential?

    <p>Independent pan heads</p> Signup and view all the answers

    In the context of overhead equipment, what material is used for the contact wire?

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

    What is the purpose of using carbon strips in pantographs?

    <p>To improve contact wire life</p> Signup and view all the answers

    What is the maximum span used for supporting overhead equipment on straight tracks?

    <p>72 m</p> Signup and view all the answers

    At what maximum interval are catenary systems normally supported on straight tracks?

    <p>72 m</p> Signup and view all the answers

    What is the diameter of the droppers supporting the contact wire?

    <p>5 mm</p> Signup and view all the answers

    How far apart are droppers spaced for the contact wire?

    <p>9 m</p> Signup and view all the answers

    What is the minimum height of contact wire under over-line structures for broad gauge (BG)?

    <p>4.65 m</p> Signup and view all the answers

    What design change is necessary for pantographs using carbon strips compared to those using steel strips?

    <p>Improved flexibility in vertical and horizontal movement</p> Signup and view all the answers

    What is the approximate speed potential of pantographs designed for carbon strips?

    <p>250 km/h</p> Signup and view all the answers

    What is the life expectancy of main contacts in Vacuum Circuit Breakers (VCB) as compared to Air Blast Circuit Breakers?

    <p>1 lakh operations</p> Signup and view all the answers

    Which of the following is an advantage of Vacuum Circuit Breakers over Air Blast Circuit Breakers?

    <p>Reduced maintenance costs</p> Signup and view all the answers

    What role does the regulating winding in a traction power transformer serve?

    <p>It chooses the appropriate voltage for traction motors</p> Signup and view all the answers

    What is the primary purpose of staggering the contact wire in the pantograph system?

    <p>To ensure uniform wear of current collecting strips</p> Signup and view all the answers

    How far does the pantograph sweep across the contact wire on straight runs?

    <p>200 mm</p> Signup and view all the answers

    What is a key difference between uninsulated and insulated overlap spans?

    <p>Uninsulated spans are 200 mm apart.</p> Signup and view all the answers

    What type of OHE system is typically used for main lines?

    <p>Regulated OHE</p> Signup and view all the answers

    At what maximum speed should section insulators be installed if their runners are facing the direction of travel?

    <p>80 km/h</p> Signup and view all the answers

    What typically bridges the electrical discontinuity at insulated overlaps?

    <p>Interrupters or isolators</p> Signup and view all the answers

    What is the distance between two contact wires in uninsulated overlap spans?

    <p>200 mm</p> Signup and view all the answers

    Why is automatic tensioning not used for certain lines?

    <p>In the interest of economy</p> Signup and view all the answers

    What is the function of section insulators in the OHE system?

    <p>To insulate one section from another</p> Signup and view all the answers

    What is a consequence if the section insulator assembly is not installed properly?

    <p>Potential arcing when passing tracks</p> Signup and view all the answers

    What character in the classification code for electric rolling stock indicates the system of power supply?

    <p>The second letter</p> Signup and view all the answers

    Which pantograph design is specifically mentioned as being suitable for operation up to 140 km/h?

    <p>AM 12 pantograph</p> Signup and view all the answers

    What does the letter 'U' represent in the classification of Multiple Unit Stock?

    <p>Multiple units</p> Signup and view all the answers

    Which pantograph improvement is mentioned as a way to enhance the life of the contact wire?

    <p>Integrating carbon strips for current collection</p> Signup and view all the answers

    What is the significance of the letter 'G' in the classification of electric locomotives?

    <p>Indicates freight service locos</p> Signup and view all the answers

    What is the primary function of a feeding post in the electric traction system?

    <p>To control supply to individual lines from the grid</p> Signup and view all the answers

    How are sectioning and paralleling posts utilized in the overhead equipment system?

    <p>To parse different zones fed from various phases</p> Signup and view all the answers

    What feature allows for the isolation of the overhead equipment at closer intervals?

    <p>Sub-sectoring with interrupters</p> Signup and view all the answers

    What essential component is provided at sections of the overhead equipment for maintenance purposes?

    <p>Earthing devices in off position</p> Signup and view all the answers

    What is the role of bridging interrupters located at sectioning and paralleling posts?

    <p>To allow power to continue from one feeding post despite interruptions</p> Signup and view all the answers

    What typically determines the spacing of traction sub-stations along electrified routes?

    <p>Intensity of traffic and load</p> Signup and view all the answers

    For localized shutdown of power supply during maintenance at watering stations, which equipment is used?

    <p>Manually operated interrupters</p> Signup and view all the answers

    What mechanism is used for ensuring rapid isolation of faults on the overhead equipment?

    <p>Sectioning at regular intervals</p> Signup and view all the answers

    What is the equivalent copper section for the catenary and contact wires together in certain sections of Waltair-Kirandul?

    <p>200 mm2</p> Signup and view all the answers

    What is the permissible current on a single track due to the equivalent cross-sectional area of overhead equipment?

    <p>600 A</p> Signup and view all the answers

    What is the maximum height for regulated overhead equipment above rail level for normal conditions?

    <p>5.60 m</p> Signup and view all the answers

    How far apart should the droppers supporting the contact wire be spaced?

    <p>9 m</p> Signup and view all the answers

    What type of wire is used for the contact wire in tramway type overhead equipment?

    <p>Grooved hard drawn copper contact wire</p> Signup and view all the answers

    What is the maximum span for supporting the catenary system on straight tracks?

    <p>72 m</p> Signup and view all the answers

    At what height can the contact wire be set in areas with a temperature range of 15°C to 65°C?

    <p>5.65 m</p> Signup and view all the answers

    What diameter is specified for the droppers supporting the contact wire?

    <p>5 mm</p> Signup and view all the answers

    What design does the cantilever type bracket assembly support the OHE from?

    <p>I section steel masts</p> Signup and view all the answers

    Which temperature limit is used for determining the permissible current on a single track?

    <p>85°C</p> Signup and view all the answers

    What is the distance the pantograph sweeps across the contact wire on curved runs?

    <p>300 mm on one side</p> Signup and view all the answers

    What is the primary function of the section insulator assembly in the OHE system?

    <p>To insulate the OHE of one elementary section from another</p> Signup and view all the answers

    What is a characteristic feature of uninsulated overlap spans?

    <p>They are permanently connected by suitable jumpers.</p> Signup and view all the answers

    What is the typical separation distance between two contact wires in uninsulated overlap spans?

    <p>200 mm</p> Signup and view all the answers

    What is the maximum speed at which section insulators should be installed if their runners overlap and are facing the direction of travel?

    <p>80 km/h</p> Signup and view all the answers

    For what type of lines is unregulated OHE typically used?

    <p>Isolated, large yard lines and unimportant lines</p> Signup and view all the answers

    What is the distance at which the overlap of OHE conductors is generally terminated?

    <p>1.5 km</p> Signup and view all the answers

    What device is typically used to bridge electrical discontinuity at insulated overlaps?

    <p>Isolators or interrupters</p> Signup and view all the answers

    What ensures uniform wear of the current collecting strips of the pantograph?

    <p>The staggered contact wire design</p> Signup and view all the answers

    What adjustment is made to the height of the conductor at overlaps?

    <p>It matches the height of the pantograph.</p> Signup and view all the answers

    What precaution should be taken when closing bridging interrupters?

    <p>They should be closed only after the rules are followed.</p> Signup and view all the answers

    Which statement accurately describes a Neutral Section?

    <p>It separates areas fed by adjacent substations for safety.</p> Signup and view all the answers

    What is the function of an Auxiliary transformer at switching stations?

    <p>To provide 240 V, 50 Hz for signaling and lighting.</p> Signup and view all the answers

    What type of equipment is provided to protect against voltage surges in a sub-sector?

    <p>Lightning arresters.</p> Signup and view all the answers

    Why are remote control equipment and batteries housed in a masonry cubicle?

    <p>To isolate from weather and environmental elements.</p> Signup and view all the answers

    What is a requirement for the location of neutral sections?

    <p>On level tangent tracks far from distractions.</p> Signup and view all the answers

    What is the purpose of warning boards before a neutral section?

    <p>To inform the Loco pilot to open the circuit breaker.</p> Signup and view all the answers

    How many interrupters are typically provided at a Sub-Sectioning Post (SSP) for double track sections?

    <p>Three, connecting up and down tracks.</p> Signup and view all the answers

    What feature distinguishes Sub-Sectioning Posts (SS) from Sub-Sectioning Posts (SSP)?

    <p>SSs allow sectioning but not paralleling.</p> Signup and view all the answers

    What is the role of potential transformers at switching stations?

    <p>To monitor power supply to each sub-sector.</p> Signup and view all the answers

    Study Notes

    Bridging Interrupters

    • Bridging interrupters are normally open and should only be closed with special precautions.
    • Interrupters are designed to prevent the pantograph of an electric locomotive from bridging different phases of the 25kV supply.

    Sub-Sectioning and Paralleling Posts (SSP)

    • SSPs are located between each feeding post and adjacent sub-sectioning post.
    • SSPs connect adjacent sub-sectors of up and down tracks in a double track section.

    Sub-Sectioning Post (SS)

    • SSs are located only occasionally.
    • SSs are similar to SSPs but do not have paralleling capabilities.

    Neutral Section

    • A neutral section is a short, insulated and dead section of overhead equipment.
    • Neutral sections separate areas fed by different substations or feeding posts.
    • Neutral sections are located on level tangent tracks.
    • Loco pilots must open the locomotive circuit breaker and coast through the neutral section.

    Important Equipment at Switching Stations:

    • Lightning Arresters: protect each sub-sector against voltage surges.
    • Auxiliary Transformers: provide a 240V, 50Hz AC supply for signaling and operational lighting.
    • Potential Transformers: monitor the supply to each sub-sector.
    • Remote Control Equipment: accommodate control panel, telephone, batteries, and battery chargers.

    Overhead Equipment

    Catenary and Contact Wires:

    • Catenary wire is made of stranded cadmium copper (65mm2) or stranded aluminium alloy (116mm2).
    • Contact wire is made of grooved hard drawn copper (107mm2) and is suspended from the catenary by droppers.
    • The combined cross-sectional area of catenary and contact wire is 157mm2.
    • The current permissible on a single track is approximately 600A.
    • Some sections have an equivalent copper cross-section of 200mm2.

    Height of Contact Wire:

    • Regulated OHE contact wire height is 5.60m above rail level.
    • Unregulated OHE contact wire height is 5.75m or 5.65m based on temperature ranges.
    • Height can be reduced (4.65m BG, 4.02m MG) under over-line structures.

    Span of Supporting Mast/Structures:

    • Spans vary from 72m on straight tracks to 27m on curved tracks.
    • Catenary is supported at a maximum interval of 72m (63m on MG) on straight tracks.

    Stagger:

    • The contact wire is staggered to ensure uniform wear of the pantograph's current collecting strips.
    • Stagger is 200mm on straight tracks and 300mm on curves.

    Overlaps:

    • Overlaps occur at intervals of 1.5km and facilitate smooth pantograph transition.
    • Uninsulated Overlaps: Two contact wires are connected by jumpers with 200mm separation.
    • Insulated Overlaps: Two OHE systems are 500mm apart and are connected by interrupters.

    Regulated and Unregulated OHE

    • Regulated OHE uses automatic tensioning and is used for main lines.
    • Unregulated OHE is used for yards and unimportant lines for economic reasons.

    Section Insulator Assembly:

    • Section insulators isolate the OHE of one elementary section from the next.
    • Section insulators are positioned at cross-overs, allowing current collection to shift between tracks smoothly.
    • Maximum speed for section insulator assemblies with trailing runners is 120km/h.
    • Maximum speed for section insulator assemblies with facing runners or not installed within the first third of the span is 80kmh.

    Electric Rolling Stock

    Classification of Electric Rolling Stock:

    • Locos and EMUs are classified with a three/four letter code followed by a class number.
    • Gauge: W (BG) or Y (MG).
    • Power Supply: A (AC), C (DC), CA (DC & AC).
    • Locos: M (Mixed Traffic), G (Freight), P (Passenger), S (Shunting).
    • EMUs: U.

    Important Equipment of Electric Loco/EMU:

    • Pantograph:

      • AM12 pantograph is used for 25kV AC electric locomotives and EMUs.
      • It uses steel strips for current collection and is operated by a pneumatic servo motor.
      • The suspension is on plungers and is suitable for operation up to 140kmh.
      • Improved pantographs with lower dynamic mass and independent pan heads are used for higher speeds (250kmh).
      • Carbon strips can be used for better lifespan of the contact wire, demanding more flexible pan head design.

    • Circuit Breaker:

      • Air Blast Circuit Breaker: Breaks fault current with a breaking capacity of 250MVA.
      • Vacuum Circuit Breaker (VCB): Introduced in 1985.
        • Simplified design with fewer parts.
        • Self-contained interrupting medium (vacuum).
        • Higher life expectancy (1 lakh operations).
        • Reduced size, weight, and maintenance cost.
        • Faster trip-time (less than 60 milliseconds).
        • Handles fault currents during closing (making capacity of 250MVA).

    • Transformer:

      • Steps down 25kV AC single-phase power from the contact wire.
      • Contains primary, regulating, traction secondary, and auxiliary windings.
      • Regulating winding adjusts voltage for traction motors.
      • Auxiliary winding powers auxiliary motors.
      • Increases the horsepower of the locomotive.

    • Traction Motors:

      • Convert electrical energy to mechanical energy.
      • Usually DC motors used for locomotive propulsion.
      • Connected to the transformer's secondary winding.
      • Control the speed and torque of the locomotive.
      • Can be series-wound or separately-excited.

    • Braking System:

      • Used to stop or slow down the locomotive.
      • Can be electric, pneumatic, or a combination.
      • Electric braking uses traction motors as generators to create resistance.
      • Pneumatic braking uses air pressure to apply brakes to the wheels.

    • Control System:

      • Controls the operation of the locomotive.
      • Includes throttle, brakes, and various electrical switches.
      • Can be manual or automatic.

    Power Supply

    • Electric traction uses a 25kV, AC, 50Hz single-phase power supply.
    • Power is supplied from the State Electricity Boards through traction sub-stations.
    • Sub-stations are located 35-50km apart, with distances varying based on traffic volume and train load.

    Overhead Equipment Sectioning

    • Overhead equipment (OHE) is sectioned to isolate faults and facilitate maintenance.
    • Sections are typically 10-15km long.
    • Each section contains:
      • Switching Stations: Include interrupters rated at 600A to isolate the section.
      • Sub-Sectors: The shortest section that can be isolated by interrupters alone.
      • Elementary Sections: Smaller sections within the sub-sector, isolated by manual isolator switches.

    Types of Switching Stations

    • Feeding Post (FP): Incoming power is fed from the grid substation. Each feeder supplies OHE on one side of the FP through interrupters.
    • Sectioning and Paralleling Post (SP): Located midway between FP's, marking the boundary between zones.
      • Paralleling interrupter: Parallels OHE for up and down tracks on double-track sections.
      • Bridging interrupter: Allows one FP to feed beyond the SP if its supply is interrupted (remains open unless necessary).
    • Sub-Sectioning and Paralleling Post (SSP): One or more per FP/SP pair.
      • Three interrupters connect adjacent sub-sectors of up and down tracks on double-track sections.
    • Sub-Sectioning Post (SS): Similar to SSP but without paralleling.

    Neutral Section

    • An insulated "dead zone" separating areas fed by different sub-stations.
    • Prevents pantographs from bridging phases while transitioning between sub-stations.
    • Loco pilots must open circuit breakers before entering and after exiting neutral sections.
    • Located on level tangent tracks to avoid stalling during coasting through the section.

    Equipment at Switching Stations

    • Lightning Arresters: Protect sub-sectors from voltage surges.
    • Auxiliary Transformers: Provide 240V, 50Hz AC for signaling and lighting.
    • Potential Transformers: Monitor power supply to individual sub-sectors.
    • Remote Control Equipment: Control panels, telephones, batteries and chargers for interrupters and other equipment.

    Overhead Equipment (OHE)

    • Catenary Wire: Stranded cadmium copper (65mm2) or aluminium alloy (116mm2).
    • Contact Wire: Grooved, hard-drawn copper (107mm2) supported by catenary via droppers.
    • Combined Equivalent Copper Section: 157mm2 for main lines, permitting 600A current.
    • Loop Lines, Sidings, Yards: Only contact wire (107mm2).

    Height of Contact Wire

    • Regulated OHE: 5.60m above rail level (with pre-sag).
    • Unregulated OHE: 5.75m (4°C to 65°C) or 5.65m (15°C to 65°C).
    • Lower heights possible under bridges, requiring special precautions for oversize loads.

    Span of Supporting Structures

    • Straight Track: Maximum 72m (63m for MG).
    • Curved Tracks: Decrees with curvature.
    • Supported by cantilever arms fixed to steel masts or structures.

    Stagger

    • Enables uniform wear of pantograph contact strips.
    • Straight Track: 200mm offset on either side of centerline.
    • Curves: 300mm offset on one side.

    Overlaps

    • OHE conductors terminated with overlaps every 1.5km to ensure smooth pantograph transition.
    • Uninsulated: 200mm separation, conductors permanently connected by jumpers.
    • Insulated: 500mm separation, bridged by interrupters/isolators except at neutral sections.

    Regulated and Unregulated OHE

    • Regulated OHE: Uses automatic tensioning, standard for main lines.
    • Unregulated OHE: Used in isolated yards and unimportant lines, for cost savings.

    Section Insulator Assembly

    • Insulates OHE of adjacent elementary sections, like at cross-overs.
    • Enables smooth current collection during transitions between tracks.
    • Assemblies with porcelain insulators are suitable for speeds up to 120km/hr when placed within the first one-third of the span.
    • Speed limit of 80km/h is required when runners are in the facing direction or section insulator assembly is placed outside the first one-third span.

    Electric Rolling Stock Classification

    • Three-letter code:
      • First letter: Gauge (W for BG, Y for MG).
      • Second letter: Power supply (A for AC, C for DC, CA for AC/DC).
      • Third letter: Service (M for mixed traffic, G for freight, P for passenger, S for shunting).
    • Four-letter code: Add "U" for Multiple Unit Stock (EMUs).

    Examples

    • AC Locomotives: WAG1, WAG2, WAG3, WAG4, WAG5, WAG6, WAG7, WAG9, WAG9M
    • AC/DC Locomotives: WCAM1
    • AC EMUs: WAU1, WAU2, WAU3, WAU4, YAU

    Important Equipment of Electric Loco/EMU

    • Pantograph: Collects power from the contact wire, mounted on the roof of vehicles.
    • AM 12 Pantograph: Widely adopted in India, uses steel strips for current collection and is pneumatically operated.
    • Pantographs for Higher Speeds: Improved design with lower dynamic mass and independent pan heads.
    • Carbon Strips: Increasingly used to enhance contact wire lifespan.

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    Description

    This quiz covers key components of electric railway systems, focusing on bridging interrupters, sub-sectioning posts, and neutral sections. Learn about their functions, locations, and operational safety measures critical for locomotive conductors. Test your understanding of essential railway electrical equipment and infrastructure.

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