Power Supply Arrangements at Sub-Stations
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What type of power supply is primarily used for electric traction?

  • 25 kV, AC, 50 Hz single phase (correct)
  • 25 kV, AC, 60 Hz single phase
  • 30 kV, AC, 50 Hz single phase
  • 20 kV, DC, 50 Hz three phase

    • What is the distance range between traction substations?

  • 25 to 30 km
  • 60 to 70 km
  • 35 to 50 km (correct)
  • 10 to 20 km

    • Which of the following arrangements is NOT mentioned for power supply at traction substations?

  • Shared ownership of feeder circuit breakers
  • Remote control operation of all equipment (correct)
  • Railways owning and operating all equipment
  • 3-phase power supply from a single grid point

    • How many single phase transformers are typically installed at each traction substation?

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

    What is the standard capacity for transformers installed at traction substations?

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

    What mechanism is used to ensure continuity of power supply at traction substations?

    <p>Double transmission line or two power sources</p> Signup and view all the answers

    What action is taken if a fault is detected in the transmission lines or substation equipment?

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

    What is the primary role of the Traction Power Controller (TPC)?

    <p>To control switching operations and maintain power supply continuity</p> Signup and view all the answers

    What kind of telecommunication lines are used along the tracks to avoid interference?

    <p>Under-ground cables and microwave transmission</p> Signup and view all the answers

    Which telephone circuit is primarily controlled by the Section Controller?

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

    How are the telephone circuits in electrified sections designed for emergency situations?

    <p>Several independent channels for quick communication</p> Signup and view all the answers

    What type of personnel operates the Dy.Control Telephone Circuit?

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

    What is the primary function of the transformers used at substations?

    <p>To step down the grid voltage to 25 kV</p> Signup and view all the answers

    What is the permissible variation of bus bar voltage at grid substations?

    <p>+10% and -5%</p> Signup and view all the answers

    What is the relationship between the single phase traction load and the supply system?

    <p>It causes unbalance in the supply system</p> Signup and view all the answers

    What is the maximum allowable continuous voltage unbalance at the point of common coupling?

    <p>2%</p> Signup and view all the answers

    What is installed on the secondary side of the transformer for operational flexibility?

    <p>One transformer circuit breaker and one feeder circuit breaker</p> Signup and view all the answers

    Which of the following statements about the traction substation is true?

    <p>It is designed for remote operation</p> Signup and view all the answers

    What equipment is used to control each feeder from the substation?

    <p>A single pole circuit breaker equipped with protective devices</p> Signup and view all the answers

    What is done to ensure the secondary winding voltage does not exceed 27.5 kV at the feeding post?

    <p>Tappings are adjusted on the secondary winding</p> Signup and view all the answers

    Why is solid earthing used at the traction substation?

    <p>To provide fault current return path through the rails</p> Signup and view all the answers

    What is the purpose of providing a Neutral Section between two substations?

    <p>To prevent electric locomotives from bridging two phases.</p> Signup and view all the answers

    What is the maximum distance between sectioning points in the overhead equipment system?

    <p>10 to 15 km</p> Signup and view all the answers

    What are manual isolator switches used for in the overhead equipment system?

    <p>To isolate and sub-divide electrical sections.</p> Signup and view all the answers

    What type of switching device is provided at watering stations?

    <p>Manual interruptors with earthing heels</p> Signup and view all the answers

    How many interruptors are typically provided at each feeding post for a two-track line?

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

    What is a 'sub-sector' in the context of overhead equipment?

    <p>The smallest isolated section using interruptors alone.</p> Signup and view all the answers

    What is the primary role of sectioning and paralleling posts?

    <p>To demarcate zones fed from adjacent substations.</p> Signup and view all the answers

    In large yards, what precaution is typically taken with alternate feeding arrangements?

    <p>Switches are locked in one position and changed with due precautions.</p> Signup and view all the answers

    Which component is used to rapidly isolate faults on overhead equipment?

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

    What critical feature is included in isolators at electric loco running sheds?

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

    What is the purpose of installing potential transformers at various switching stations?

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

    In the event of a power block on the OHE sub sectors, what is the likely impact on electric traffic?

    <p>Electric traffic must be suspended on the line.</p> Signup and view all the answers

    What is the role of the small masonry cubicle mentioned in the document?

    <p>To accommodate remote control equipment and necessary tools.</p> Signup and view all the answers

    Why are static type voltage regulators provided?

    <p>To minimize voltage fluctuations affecting signalling equipment.</p> Signup and view all the answers

    Where are the voltage regulators typically installed?

    <p>In separate kiosks or designated rooms depending on load centers.</p> Signup and view all the answers

    What additional arrangement might the S&T Department consider for large stations with considerable shunting movements?

    <p>Installing a standby diesel generator set.</p> Signup and view all the answers

    At which locations is the ac 240V supply made available through the auxiliary transformer?

    <p>At wayside stations, level crossings, and power supply installations.</p> Signup and view all the answers

    What is the maximum duration for which a power block is not likely to exceed?

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

    What is the acceptable range of voltage fluctuation allowed by the static type voltage regulators?

    <p>-5% to +5%.</p> Signup and view all the answers

    What should be kept by the S&T Department for situations when power supply is interrupted?

    <p>Portable generating sets.</p> Signup and view all the answers

    Which description best fits the role of the Traction Power Controller (TPC)?

    <p>Responsible for ensuring the uninterrupted supply of power on overhead equipment.</p> Signup and view all the answers

    What is the primary advantage of using underground cables or microwave systems for telecommunication lines?

    <p>They are immune to interference from the 25 kV single phase ac traction.</p> Signup and view all the answers

    In an electrified section, what is the main purpose of providing several independent telephone circuits?

    <p>To facilitate quick communication and coordination during operations.</p> Signup and view all the answers

    Which of the following best describes the function of the Dy.Control Telephone circuit?

    <p>Directs general traffic operations and maintains connections with key railway offices.</p> Signup and view all the answers

    What ensures the reliability of communication circuits in an emergency within an electrified section?

    <p>Multiple alternate telephone channels to replace any failed line.</p> Signup and view all the answers

    What type of voltage supply is primarily derived from the State Electricity Boards for electric traction?

    <p>25 kV, AC, 50 Hz single phase</p> Signup and view all the answers

    In how many different arrangements is the power supply at traction substations currently structured?

    <p>Four arrangements</p> Signup and view all the answers

    Which component is maintained by the Railways in the third arrangement of power supply?

    <p>25 kV feeder circuit breakers</p> Signup and view all the answers

    What is the purpose of having duplicate supply arrangements at traction substations?

    <p>To provide redundancy under failure conditions</p> Signup and view all the answers

    What is the minimum distance typically maintained between traction substations?

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

    What installation is typical at each traction substation to assure power supply reliability?

    <p>Two single-phase transformers</p> Signup and view all the answers

    What is the current standard capacity installed for transformers at traction substations?

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

    What is the maximum permissible instantaneous voltage unbalance at the point of common coupling?

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

    What is the purpose of the transformer circuit breaker in the traction substation?

    <p>To isolate faulty sections of the transformer</p> Signup and view all the answers

    Which statement best describes the typical configuration for voltage regulation at traction substations?

    <p>The secondary winding voltage is adjusted to not exceed 27.5 kV at feeding posts.</p> Signup and view all the answers

    What mechanism allows for changing from one feeder to another at the traction substation?

    <p>Bus coupler</p> Signup and view all the answers

    What is the lowest permissible continuous voltage unbalance allowed on the grid supply system?

    <p>2%</p> Signup and view all the answers

    In terms of flexibility, how is the busbar connection designed in traction substations?

    <p>To allow for smooth operation between transformers and loads.</p> Signup and view all the answers

    What problem is caused by the single phase traction load in the supply system?

    <p>It causes undesirable voltage unbalance.</p> Signup and view all the answers

    What is solid earthing designed to achieve at traction substations?

    <p>To enhance safety by grounding currents</p> Signup and view all the answers

    What is the main function of the protective devices associated with circuit breakers in traction substations?

    <p>To isolate circuits from overload or faults</p> Signup and view all the answers

    What is the primary purpose of the neutral section in an electrified train system?

    <p>To ensure the locomotive can bridge different phases safely.</p> Signup and view all the answers

    Which equipment is specifically used to protect substations from voltage surges?

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

    In a double track section, how many interruptors are typically located at each sub-sectioning and paralleling post?

    <p>Two for each track and one for paralleling</p> Signup and view all the answers

    What precaution should be taken when closing bridging interruptors?

    <p>They should be closed only after taking special precautions.</p> Signup and view all the answers

    Where are auxiliary transformers typically installed?

    <p>At posts and certain intermediate points</p> Signup and view all the answers

    What is the function of a sectioning post in an electrified train system?

    <p>To provide sectioning capabilities without paralleling</p> Signup and view all the answers

    What specific role do bridging interrupters serve in an electrified train system?

    <p>To permit one feeding post to feed beyond a sectioning post.</p> Signup and view all the answers

    What type of tracks are neutral sections ideally located on?

    <p>Level tangent tracks at considerable distances from signals</p> Signup and view all the answers

    What is the voltage and frequency of the AC supplied by auxiliary transformers?

    <p>240 V, 50Hz</p> Signup and view all the answers

    What should a driver do when approaching a neutral section with an electric locomotive?

    <p>Open the locomotive circuit breaker before coasting through.</p> Signup and view all the answers

    What is the main reason for providing automatic voltage regulators in the system?

    <p>To stabilize voltage fluctuations caused by traction load.</p> Signup and view all the answers

    In what locations is the 240V supply sourced from the auxiliary transformer?

    <p>At various designated wayside stations and level crossings.</p> Signup and view all the answers

    What happens to color light signalling during a power block on the OHE sub sectors?

    <p>It ceases to operate until power is restored.</p> Signup and view all the answers

    What is the role of the S&T Department during power interruptions at large stations?

    <p>To operate portable generating sets until supply is restored.</p> Signup and view all the answers

    What is the specific limitation imposed by the static type voltage regulators?

    <p>To stabilize voltage fluctuations to ± 5%.</p> Signup and view all the answers

    Where can static voltage regulators be installed?

    <p>In remote control cubicles or ASM rooms.</p> Signup and view all the answers

    What could be the maximum duration for which a power block is unlikely to exceed?

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

    Which of the following is NOT typically included in the small masonry cubicle?

    <p>Signalling equipment.</p> Signup and view all the answers

    What provision is made by the S&T Department for signalling equipment during rare power interruptions?

    <p>Standby diesel generator sets if necessary.</p> Signup and view all the answers

    What is the primary function of potential transformers at switching stations?

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

    Study Notes

    Power Supply Arrangements at Sub-Stations

    • 25 kV, AC, 50 Hz single-phase power supply for electric traction is derived from the grid of State Electricity Boards, with sub-stations approximately 35-50 km apart (distance can be less based on traffic intensity).
    • Four main power supply arrangements exist:
    • Supply Authorities provide 220/132/110/66 kV Extra High Voltage (EHV) power to each station, owned, installed, operated, and maintained by the Railways.
    • Railways receive 3-phase power from the Supply Authority at a single point, then run their own transmission lines and operate their own sub-stations.
    • EHV and 25 kV equipment is owned, installed, operated, and maintained by the Supply Authority, except 25 kV feeder circuit breakers are controlled by the Traction Power Controller (TPC).
    • Duplicate supply is provided for reliability:
    • High voltage feed to sub-stations is usually from two sources (or a double transmission line), with protective equipment to rapidly isolate faults in transmission lines and substation equipment.
    • Normally, two single-phase transformers are installed at each sub-station, one in service and one as a 100% standby. The standard capacity is 21.6 MVA (ONAN)/30.2 MVA (ONAF).

    Voltage Regulation

    • Voltage variation at grid sub-stations is permissible within ±10% of 27,500V, ranging between 27,500V and 23,750V.
    • Transformers are set to maintain a voltage as high as possible, but not exceeding 27.5 kV at feeding posts.

    25 kV Supply at Traction Substations

    • Each substation has one transformer circuit breaker and one feeder circuit breaker with associated double-pole isolators, providing flexibility.
    • Substations are designed for remote operation.
    • Facilities exist to change feders.
    • One end of the transformer secondary is grounded at the substation to the track/return feeder.

    Feeding and Sectioning Arrangements

    • Supply authorities' generation and transmission systems are 3-phase, but single-phase traction loads cause imbalance, affecting generators and other consumers.
    • Permissible voltage unbalance must not exceed 5% (instantaneous), 3% (2 hours), or 2% (continuous).

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    Description

    Explore the complexities of power supply arrangements for electric traction at sub-stations. This quiz covers various supply methods, equipment ownership, and strategies for maintaining reliability in power distribution. Test your knowledge of the electricity operations essential for railways.

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