Power Supply Arrangements at Sub-Stations
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Questions and Answers

What is the primary voltage for the feeders that are used to support the overhead equipment for traction?

  • 25 kV (correct)
  • 27.5 kV
  • 23.75 kV
  • 30 kV

    • What is the permissible voltage variation range for the bus bars at the grid sub-station?

  • $27,500 V$ to $23,750 V$ (correct)
  • $23,000 V$ to $29,000 V$
  • $20,000 V$ to $27,500 V$
  • $25,000 V$ to $30,000 V$

    • How is the single-phase traction load managed to prevent unbalance in the 3-phase grid system?

  • By cyclic tapping across different phases (correct)
  • By reducing the voltage to lower levels
  • By using transformers
  • By using only one phase for traction

    • Which component ensures that the voltage does not exceed 27.5 kV at the feeding post?

    <p>Transformer settings</p> Signup and view all the answers

    What is the maximum allowable instantaneous voltage unbalance at the point of common coupling in the grid supply system?

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

    What type of operation is the traction sub-station designed for?

    <p>Remote operation</p> Signup and view all the answers

    What connects one end of the secondary winding of the transformer at the sub-station?

    <p>Buried rail</p> Signup and view all the answers

    What is the maximum speed allowed when the runners of the section insulator assembly are not installed in the first one-third of the span?

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

    What kind of structures are used to ensure mechanical independence of the overhead equipment (OHE) for each track?

    <p>Independent structures</p> Signup and view all the answers

    What is the maximum speed potential for an OHE designed with a span of 72 m and a tension of 1000 kgf in both contact and catenary wires?

    <p>160 km/h</p> Signup and view all the answers

    What precaution is necessary when approaching an unwired track with an electric locomotive?

    <p>A diesel engine must be used to pull the locomotive</p> Signup and view all the answers

    What should a driver be ready to do when approaching a neutral section indicated by warning boards?

    <p>Open the DJ (Disconnector Junction)</p> Signup and view all the answers

    What is indicated about electric traffic during a power block on both OHE sub-sectors?

    <p>Electric traffic must be suspended until power is restored.</p> Signup and view all the answers

    What is the purpose of static type voltage regulators in the railways?

    <p>To maintain voltage fluctuations within + 5%.</p> Signup and view all the answers

    Where are static type voltage regulators typically installed?

    <p>Inside dedicated kiosks or rooms based on load positions.</p> Signup and view all the answers

    What is the duty of the Traction Power Controller (TPC) during his shift?

    <p>To monitor and maintain continuity of power supply.</p> Signup and view all the answers

    What kind of emergency provision can be found at large stations?

    <p>Standby diesel generator sets installed by S&amp;T.</p> Signup and view all the answers

    How often is the Remote Control Centre (RCC) manned?

    <p>24 hours a day.</p> Signup and view all the answers

    What is the maximum duration a power block is likely to last?

    <p>One hour at a time.</p> Signup and view all the answers

    Which of the following personnel is in charge of switching operations on the railway system?

    <p>The Traction Power Controller (TPC).</p> Signup and view all the answers

    What arrangement is suggested for authority communication during a power block?

    <p>Close liaison with Section Controllers.</p> Signup and view all the answers

    What is the purpose of staggering the contact wire in OHE systems?

    <p>To allow the pantograph to sweep across the current collecting strips.</p> Signup and view all the answers

    What defines a regulated OHE system?

    <p>It incorporates automatic tensioning mechanisms.</p> Signup and view all the answers

    How far apart are uninsulated overlap spans in OHE systems?

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

    What is the role of section insulators in OHE systems?

    <p>To isolate adjacent elementary sections from each other.</p> Signup and view all the answers

    Why are insulated overlaps provided in OHE systems?

    <p>To prevent arcing and ensure safety.</p> Signup and view all the answers

    What is the maximum distance OOHE conductors can be terminated with an overlap?

    <p>1.5 Km.</p> Signup and view all the answers

    What factor typically dictates the spans adopted for catenary support intervals?

    <p>Degree of curvature.</p> Signup and view all the answers

    What happens when pantographs transition between OHE systems?

    <p>They can cause sparks if not designed correctly.</p> Signup and view all the answers

    What is the length of overlap in insulated overlaps in OHE systems?

    <p>500 mm.</p> Signup and view all the answers

    At what speed are section insulator assemblies designed to be effective?

    <p>120 km/h.</p> Signup and view all the answers

    What is the primary purpose of the Emergency Control Circuit?

    <p>To facilitate quick communication between traction maintenance gangs and TPC.</p> Signup and view all the answers

    Where are emergency telephone socket boxes installed?

    <p>Along the track at specific intervals and near important posts.</p> Signup and view all the answers

    Which of the following is NOT a purpose of walkie-talkie sets in maintenance depots?

    <p>To interact with passengers.</p> Signup and view all the answers

    Who primarily operates the Emergency Control Circuit?

    <p>TPC (Traction Power Control).</p> Signup and view all the answers

    What is the role of Hot Line Communication?

    <p>To establish a connection between headquarters and electric loco sheds.</p> Signup and view all the answers

    What interval is recommended for placing emergency telephone socket boxes along the track?

    <p>Every 0.75 to 1 km.</p> Signup and view all the answers

    Which of the following is a function of the independent inter-communication circuit?

    <p>To facilitate local communication among Section Controllers and Chief Controller.</p> Signup and view all the answers

    Which personnel are equipped with portable emergency telephones?

    <p>Train crew, maintenance gangs, and Station Masters.</p> Signup and view all the answers

    What is a key benefit of providing walkie-talkie sets in maintenance depots?

    <p>Improving efficiency and productivity during maintenance and breakdowns.</p> Signup and view all the answers

    Which of the following roles is NOT involved in the Hot Line Communication circuit?

    <p>Traffic Control Officers.</p> Signup and view all the answers

    What is the standard capacity of the transformers typically installed at traction sub-stations?

    <p>21.6 MVA (ONAN)/30.2 MVA (ONAF)</p> Signup and view all the answers

    Which arrangement describes when the Railway owns certain circuit breakers at sub-stations while the Supply Authority manages all other equipment?

    <p>Railway owns feeder circuit breakers but not transformers</p> Signup and view all the answers

    How is continuity of power supply ensured at traction sub-stations?

    <p>Through dual power sources or double circuit transmission line</p> Signup and view all the answers

    What is a typical distance between traction sub-stations along electrified sections?

    <p>35 to 50 km</p> Signup and view all the answers

    Which of the following explosion prevention measures is commonly installed at traction sub-stations?

    <p>Rapid fault isolation equipment</p> Signup and view all the answers

    How does the Railway receive its power supply if it runs its own transmission lines?

    <p>From a single 3-phase power supply point near the grid sub-station</p> Signup and view all the answers

    What is the role of the Traction Power Controller regarding the 25 kV feeder circuit breakers?

    <p>To operate feeder circuit breakers remotely</p> Signup and view all the answers

    What is the main function of the Emergency Control Circuit in the railway system?

    <p>To facilitate the communication between traction maintenance gangs and TPC during emergencies</p> Signup and view all the answers

    Which personnel are typically provided with portable emergency telephones?

    <p>Train crew, maintenance gangs, and Station Masters</p> Signup and view all the answers

    What interval is recommended for the placement of emergency telephone socket boxes along the railway track?

    <p>Every 0.75 to 1 km</p> Signup and view all the answers

    What purpose do walkie-talkie sets serve in maintenance depots?

    <p>To enhance communication during power blocks and maintenance activities</p> Signup and view all the answers

    What does the Hot Line Communication circuit primarily connect?

    <p>Divisional HQ traction loco controller to electric loco sheds and senior officials</p> Signup and view all the answers

    What is the purpose of a 'Neutral Section' in the overhead equipment system?

    <p>To ensure that pantographs do not bridge different phases</p> Signup and view all the answers

    What is referred to as a 'sub-sector' in the overhead equipment management?

    <p>A section that can be isolated by opening interruptors alone</p> Signup and view all the answers

    Why are warning boards placed in advance of the neutral section?

    <p>To alert drivers to open the locomotive circuit breaker</p> Signup and view all the answers

    What are 'interruptors' used for at feeding posts?

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

    What feature does a sectioning and paralleling post (SP) provide?

    <p>It marks the boundary of two zones with different power phases</p> Signup and view all the answers

    What type of isolators are provided for electric loco running sheds?

    <p>Isolators with earthing device in the 'off' position</p> Signup and view all the answers

    How are 'elementary sections' created in the overhead equipment system?

    <p>Using off-load type manually operated isolator switches</p> Signup and view all the answers

    What does the term 'earthing heels' refer to in the context of overhead equipment?

    <p>Devices used to ground the overhead equipment safely</p> Signup and view all the answers

    What is the expected functionality of manually operated interrupters at watering stations?

    <p>To enable local power disconnection and earthing</p> Signup and view all the answers

    What is the role of the bridging interruptors in the overhead equipment system?

    <p>To allow one feeding post to supply power beyond its sectioning post.</p> Signup and view all the answers

    What type of equipment is typically installed to protect each sub-sector from voltage surges?

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

    How many interruptors are normally provided at each Sub-Sectioning Post (SSP) in a double track section?

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

    Where is the 25 kV AC supply tapped to ensure a reliable supply of 240V?

    <p>At each wayside station for CLS and level crossings more than 2 km from a station</p> Signup and view all the answers

    What is the primary purpose of auxiliary transformers installed at posts?

    <p>To supply AC at 240 V, 50 Hz for lighting and signaling</p> Signup and view all the answers

    What occurs with the bridging interruptors under normal operation conditions?

    <p>They are normally kept open.</p> Signup and view all the answers

    What type of posts are occasionally used for sectioning but do not support paralleling of tracks?

    <p>Sub-Sectioning Post (SS)</p> Signup and view all the answers

    What provides accommodation for remote control equipment and other essential devices?

    <p>Masonry cubicle</p> Signup and view all the answers

    What is typically monitored at switching stations using potential transformers?

    <p>Power supply to each sub-sector</p> Signup and view all the answers

    What is the role of lightning arresters in the sub-sector equipment?

    <p>To protect against voltage surges</p> Signup and view all the answers

    What is the primary purpose of the Traction Loco Control circuit?

    <p>To manage the movements of electric locomotives and EMU stock</p> Signup and view all the answers

    Which circuit is primarily responsible for train movements within a section?

    <p>Train Control/Section Control</p> Signup and view all the answers

    What type of communication does the Traction Power Control circuit focus on?

    <p>Power supply and switching operations</p> Signup and view all the answers

    Which personnel primarily operates the Dy.Control Telephone circuit?

    <p>Deputy Controller</p> Signup and view all the answers

    What is a key benefit of having multiple independent telephone circuits in electrified railway sections?

    <p>To enable quick communication and coordination</p> Signup and view all the answers

    Which circuit is specifically used for continuous monitoring of wagon movements?

    <p>Stock Control Telephone</p> Signup and view all the answers

    Which of the following offices is NOT connected to the Train Control/Section Control circuit?

    <p>Stock Control Offices</p> Signup and view all the answers

    For managing all power supply communications, which circuit is utilized?

    <p>Traction Power Control</p> Signup and view all the answers

    Which of the following statements accurately describes the role of the Section Controller?

    <p>Directing train movements within their jurisdiction</p> Signup and view all the answers

    The connections for the Traction Loco Control circuit include which of the following?

    <p>Electric Loco Sheds and Important Station Masters</p> Signup and view all the answers

    Study Notes

    Power Supply Arrangements at Sub-Stations

    • 25 kV, 50 Hz single-phase power supply for electric traction is derived from the grid system of State Electricity Boards.
    • Sub-stations are located approximately 35-50 km apart (or less depending on traffic and load) along electrified sections.
    • Four primary arrangements exist for power supply:
      • Supply Authorities provide 220/132/110/66 kV EHV at the sub-station.
      • Railways receive 3-phase power from the Supply Authority, maintain their own transmission lines, and operate sub-stations.
      • Supply Authority owns all EHV and 25 kV equipment, except 25 kV feeder circuit breakers owned by the Railways.
      • Supply Authority owns all EHV and 25 kV equipment, except 25 kV feeder circuit breakers operated remotely by the Traction Power Controller (TPC).

    Duplicate Power Supply

    • Double circuit transmission lines or dual power sources ensure uninterrupted power supply in sub-stations.
    • Protective equipment isolates any fault in transmission lines or sub-station equipment quickly.
    • Normally, two single-phase transformers (21.6/30.2 MVA capacity) are used to step down the grid voltage to 25 kV and feed traction equipment.
    • 25 kV feeders carry power from sub-stations to feeding posts, controlled by circuit breakers with protective devices.

    Voltage Regulation

    • Permissible busbar voltage variation at the grid sub-station is +10% and -5% (27,500 V to 23,750 V).
    • Transformer tappings regulate voltage at the feeding posts (maximum 27.5 kV).
    • Multiple transformer circuits on the secondary side include a transformer circuit breaker and feeder circuit breaker with associated double pole isolators.

    Feeding and Sectioning Arrangements

    • 3-phase supply systems from power authorities create supply imbalances affecting generators and other equipment.
    • Voltage unbalance at the point of common grid coupling should not exceed 5% (instantaneous) or 3% (continuous).
    • Tapping off single-phase traction power from grid phases at substations (in a cyclic order) helps reduce imbalance.
    • Overhead equipment systems in adjacent sub-stations are electrically separated by "neutral sections."
    • Switching stations and other equipment segment 10-15 km sections of overhead equipment (OHE), facilitating rapid isolation for maintenance.
    • Alternative feeding arrangements are provided for yards and electric loco-running sheds.
    • Automatic switching mechanisms on some sections allow flexible power supply (e.g., for watering stations or for maintenance on OHE).

    Feeding Posts (FP)

    • Each feeder supplies OHE on one side of the feeding post through interruptors.
    • Two-track lines require four interruptors at each post.

    Sectioning and Paralleling Posts (SP)

    • Located midway between feeding posts (marking neutral sections).
    • Connect adjacent substations for better load distribution.

    Sub-Sectioning and Paralleling Posts (SSP)

    • Provided between FP and adjacent SPs, typically with three interruptors.
    • Help to divide sections of OHE into smaller segments.
    • May include interruptors or other switch gear to help divide up the section into sub-sectors.

    Other Equipment at Switching Stations

    • Essential equipment: Lightning arrestors, auxiliary transformers (240 V AC), potential transformers, controls, and communication equipment.
    • All of this equipment safeguards transmission lines and monitors the power grid, protecting against potential damage.

    Power Supply for Signaling

    • 240V AC supply is made available at railway stations and other locations through auxiliary transformers.
    • Locations include the side of tracks, level crossings, and installations.

    Remote Control and Communication

    • Remote Control Centre (RCC) manages circuit breakers and related switch gear in sub-stations.
    • One or more Traction Power Controllers (TPCs) operate switching functions during each shift.
    • Continuous communication between TPCs and Section Controllers maintains power supply and train operations.
    • Telecommunication lines (now largely underground cable/microwave) are necessary to accommodate the electrification.

    Overhead Equipment (OHE)

    • Catenary and contact wire system (cadmium copper/aluminum alloy).

    • Grooved contact wire with a specific cross-section (equivalent copper section of 157 mm²) and is supported by droppers.

    • Looping lines, sidings, yards use a simpler OHE design with lower contact wire specifications than main lines.

    • Contact wire height varies based on temperature and gauge.

    • Spans for structures supporting OHE vary based on track straightness; larger spans used in straight sections/smaller spans in curved sections.

    • The contact wire is properly staggered to ensure consistent pantograph contact/uniform wear.

    • Two types of overlap spans.

    Special Warning Signals

    • Visual cues indicating neutral sections (and when they're being used), helping drivers to operate safely and smoothly.
    • Warnings are used for unwired tracks, or when the OHE ends.

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    Related Documents

    Indian Railways AC Traction Manual Volume 1 PDF

    Description

    This quiz explores the various power supply arrangements at sub-stations, specifically focusing on electric traction systems. It covers the distances between sub-stations, the roles of supply authorities, and the strategies for ensuring a reliable power supply. Gain insights into the technical aspects that keep the electric railways running smoothly.

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