Air-Insulated Substations (AIS) - Part 1: Bus Conductor Materials
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Questions and Answers

What is the main material used for bus conductors in air-insulated substations?

  • Copper
  • Aluminum (correct)
  • Steel
  • Brass

    • What is the approximate conductivity of aluminum compared to copper?

  • 70-80%
  • 50-60% (correct)
  • 40-50%
  • 60-70%

    • What effect do larger aluminum conductor diameters have?

  • Greater conductivity
  • Reduced sag
  • More corona (correct)
  • Less wind and ice loads

    • For the same ampacity, how does the weight of copper conductors compare to that of aluminum conductors?

    <p>Copper conductors weigh twice as much</p> Signup and view all the answers

    What can be utilized for outdoor substation buses where they can be easily bent and joined?

    <p>Flat bars</p> Signup and view all the answers

    What limits the number of bars that can be grouped together for heat dissipation?

    <p>Skin and proximity effects</p> Signup and view all the answers

    What is the main limitation of using flat bars for conductors?

    <p>Corona at higher voltages</p> Signup and view all the answers

    What factors are used for the size selection of flexible conductors?

    <p>Ampacity, strength, weight, and diameter</p> Signup and view all the answers

    What is the usual limit for conductor temperature rise under normal operating conditions?

    <p>$30^oC$</p> Signup and view all the answers

    What is the emissivity for heavily weathered aluminum conductors?

    <p>0.5</p> Signup and view all the answers

    What is the operating principle of a circuit breaker (CB)?

    <p>It maintains uninterrupted current flow</p> Signup and view all the answers

    What causes the heat required to ionize the medium and strike an arc between contacts in a circuit breaker?

    <p>Small contact area</p> Signup and view all the answers

    Which factors are responsible for maintaining an arc between contacts in a circuit breaker?

    <p>$P.d.$ between the contacts and ionized particles between contacts</p> Signup and view all the answers

    What is the main goal of the high resistance method of arc extinction in circuit breakers?

    <p>To rapidly increase arc resistance</p> Signup and view all the answers

    What is the purpose of the low resistance or current zero method of arc extinction in circuit breakers?

    <p>$To$ $rapidly$ $extinguish$ $the$ $arc$</p> Signup and view all the answers

    What is the main purpose of disconnectors in switchgear installations?

    <p>To isolate networks or sections galvanically</p> Signup and view all the answers

    What type of disconnectors is suitable for rated voltages of 72.5 kV to 420 kV?

    <p>Two-column rotary disconnectors</p> Signup and view all the answers

    What is the maximum current that disconnectors are suitable for switching?

    <p>$0.5 A$</p> Signup and view all the answers

    What forms a horizontal isolating distance in the open position for two-column rotary disconnectors?

    <p>Rotating bases</p> Signup and view all the answers

    What is the purpose of the interlocking mechanism in disconnectors?

    <p>To prevent contacts from opening at high short-circuit currents</p> Signup and view all the answers

    What distinguishes two-column rotary disconnectors from other types?

    <p>They have swivel heads with the arms and HV contacts</p> Signup and view all the answers

    What is the main function of a pantograph disconnector?

    <p>Requiring less space than other designs</p> Signup and view all the answers

    For what voltage range is the two-column vertical break disconnector preferred?

    <p>170 kV</p> Signup and view all the answers

    What is the purpose of the rotating insulator in the two-column vertical break disconnector?

    <p>Transmitting actuating force to gearbox</p> Signup and view all the answers

    What is the main advantage of three-column rotary disconnectors?

    <p>Smaller pole spacings and higher mechanical terminal loads</p> Signup and view all the answers

    What is the function of earthing switches in disconnectors?

    <p>Locating at the fixed contact system</p> Signup and view all the answers

    What is the primary characteristic of the two-column rotary disconnector?

    <p>Allowing smaller pole spacings and higher mechanical terminal loads</p> Signup and view all the answers

    What is a specific feature of pantograph disconnectors in terms of switch status visibility?

    <p>Clear visibility of switch status with vertical isolating distance</p> Signup and view all the answers

    At what voltage range does the three-column rotary disconnector type operate?

    <p>≥ 145 kV</p> Signup and view all the answers

    What are the main components of the pantograph disconnector?

    <p>Scissors arms (1), Bearing frame (2), Support insulator (3), Rotating insulator (4), Motor operating mechanism (5)</p> Signup and view all the answers

    What is the role of the tie-rod in the two-column vertical break disconnector?

    <p>Transmitting actuating force from the mechanism to the contact arm with rotary bearings, rotating insulator and gearbox.</p> Signup and view all the answers

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