Transmission Line Efficiency, Power Factor, and Ferranti Effect Quiz
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Questions and Answers

What type of vibrations are characterized by high frequency and low amplitude?

  • High frequency and low amplitude vibrations (correct)
  • High frequency and high amplitude vibrations
  • Low frequency and low amplitude vibrations
  • Low frequency and high amplitude vibrations

    • In an extra high voltage transmission line, what does the propagation constant 'b = 0.00127 radians per km' represent?

  • The power factor of the line
  • The percentage ratio of line length to wavelength
  • The current ripple in the line
  • The impedance per unit length of the line (correct)

    • Which item in List-I matches with 'reduce the Ferranti effect' in List-II?

  • reduce the current ripples
  • reduce the Ferranti effect
  • increase the power flow in line
  • improve power factor (correct)

    • What is the total impedance of a lossless overhead EHV line operating at 50 Hz if the total reactance and suspectance are 0.045 pu and 1.2 pu respectively?

    <p>1.2 pu</p> Signup and view all the answers

    Which type of capacitor is used to increase the power flow in a line according to List-I and List-II matching?

    <p>series capacitor</p> Signup and view all the answers

    What is the formula for calculating wavelength given the propagation constant 'b = 0.00127 radians per km'?

    <p>$\frac{2\pi}{b}$</p> Signup and view all the answers

    What is the efficiency of the transmission line?

    <p>80%</p> Signup and view all the answers

    For the same voltage boost, where is the reactive power capacity higher?

    <p>Shunt capacitor</p> Signup and view all the answers

    In which type of transmission lines does Ferranti effect not occur?

    <p>Short transmission lines</p> Signup and view all the answers

    How can Ferranti effect be compensated?

    <p>Both a and b</p> Signup and view all the answers

    Which method is typically used to change power factor from leading to lagging?

    <p>Shunt reactor</p> Signup and view all the answers

    What is the load angle if the transmission line has a reactance of 1 Pu, and the generator is delivering 0.5 Pu of active power?

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

    What type of impedance does an overhead transmission line have?

    <p>400 Ω – 600 Ω</p> Signup and view all the answers

    In a hydroelectric power plant, the amount of electrical energy generated depends significantly on:

    <p>Head of water</p> Signup and view all the answers

    What is the correct formula to calculate the maximum sag in a conductor with a given span, weight, and working tension?

    <p>$s=WL^2/8T$</p> Signup and view all the answers

    If the weight of a conductor is 150 kg/m, ice weight is 60 kg/m, and wind force is 200 kg/m, what will be the resultant weight per meter of length using the given formula?

    <p>468 kg/m</p> Signup and view all the answers

    What factors determine the electrical energy generation capability of a hydroelectric power plant?

    <p>Head of water and Specific weight of water</p> Signup and view all the answers

    What is the type of impedance for an overhead transmission line ranging between 300 Ω and 900 Ω?

    <p>$√(C/L)$</p> Signup and view all the answers

    What happens to the inductance per unit length of a transmission line if the distance between the conductors is doubled?

    <p>Increases but not double</p> Signup and view all the answers

    In a lossless radial transmission line with surge impedance loading, what is the VAR situation at the sending and receiving ends?

    <p>Total negative VAR at sending end and zero VAR at receiving end</p> Signup and view all the answers

    Why is shunt compensation in an extra high voltage (EHV) system resorted to?

    <p>Reduce the fault level</p> Signup and view all the answers

    Which of the following circuits is most like the equivalent circuit of a short transmission line?

    <p>Series RL circuit</p> Signup and view all the answers

    What does the inductance per unit length of an overhead line due to internal flux linkages depend on?

    <p>Is independent of the size of conductor and constant</p> Signup and view all the answers

    How is the insulation of modern extra high voltage (EHV) lines designed?

    <p>The switching voltage</p> Signup and view all the answers

    What is one of the advantages of higher transmission voltage?

    <p>Increased power transfer capability of the transmission line</p> Signup and view all the answers

    How can the maximum power transfer capability of a transmission line be increased?

    <p>Parallel transmission lines</p> Signup and view all the answers

    What is one of the objectives of a power system?

    <p>Supplying rated voltage and frequency to consumers</p> Signup and view all the answers

    In an EHV system, why is shunt compensation applied?

    <p>To improve the stability</p> Signup and view all the answers

    Where does the zero-sequence current exist in a Y-delta transformer with Y-side grounded?

    <p>Exists in the lines on the delta side</p> Signup and view all the answers

    Which matrix reveals the topology of a power system network?

    <p>Bus incidence matrix</p> Signup and view all the answers

    Study Notes

    Transmission Lines

    • High frequency and low amplitude vibrations or high frequency and high amplitude vibrations are not suitable for transmission lines.
    • An extra high voltage transmission line can be approximated by a lossless line having a propagation constant b = 0.00127 radians per km.
    • The percentage ratio of line length to wavelength can be calculated using the formula LEMDA = 2π/B.

    Shunt and Series Capacitors/Reactors

    • Shunt capacitors are used to improve power factor, reduce Ferranti effect, and increase power flow in a line.
    • Series capacitors are used to reduce the current ripples, increase power flow in a line, and reduce Ferranti effect.
    • Shunt reactors are used to reduce the Ferranti effect and improve power factor.
    • Series reactors are used to reduce the current ripples.

    Efficiency of Transmission Line

    • The efficiency of a transmission line can be calculated using the formula: Efficiency = (Output power / Input power) * 100%.

    Power Factor Correction

    • Shunt capacitors can be used to change power factor from leading to lagging.
    • Shunt reactors can be used to change power factor from lagging to leading.

    Transmission Line Characteristics

    • The characteristics impedance of a loss free transmission line is √(L/C).
    • The range of surge impedance for an overhead transmission line is 300 Ω – 900 Ω.
    • The inductance per unit length of an overhead line due to internal flux linkages depends on the size of the conductor.

    Hydroelectric Power Plant

    • The amount of electrical energy that can be generated by a hydroelectric power plant depends on the head of water, quantity of water, and specific weight of water.

    Overhead Transmission Line Conductors

    • Aeoline vibrations are a type of vibration that occurs in overhead transmission line conductors due to wind.
    • The weight of conductor, weight of ice, and wind force can affect the sag of the conductor.

    Radial Transmission Line

    • A lossless radial transmission line with surge impedance loading has a flat voltage profile and unity power factor at all points along it.

    Equivalent Circuit of Short Transmission Line

    • The equivalent circuit of a short transmission line is a series RL circuit.

    Objectives of Power System

    • The objectives of a power system include to minimize the cost of electrical energy per KWh, to supply rated voltage and frequency to the consumers, and to maximize power transfer capability.

    ZBUS Matrix

    • The ZBUS matrix is a sparse matrix that reveals the topology of the power system network.
    • The Bus incidence matrix, Primitive impedance matrix, Primitive admittance matrix, and Bus impedance matrix are all related to the ZBUS matrix.

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    Description

    Test your knowledge on power transmission efficiency, power factor, and Ferranti effect in single-phase transmission lines. Calculate efficiency, compare reactive power capacities, and identify scenarios where Ferranti effect does not occur.

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