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

What is the efficiency of the transmission line?

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

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

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

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

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

How can Ferranti effect be compensated?

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

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

<p>Shunt reactor (C)</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>$30°$ (C)</p> Signup and view all the answers

What type of impedance does an overhead transmission line have?

<p>400 Ω – 600 Ω (D)</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 (B)</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>$s=WL^2/8T$ (C)</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 (C)</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 (A)</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>$√(C/L)$ (B)</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 (A)</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 (A)</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 (B)</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 (B)</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 (A)</p> Signup and view all the answers

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

<p>The switching voltage (D)</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 (C)</p> Signup and view all the answers

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

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

In an EHV system, why is shunt compensation applied?

<p>To improve the stability (D)</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 (B)</p> Signup and view all the answers

Which matrix reveals the topology of a power system network?

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

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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 = 2Ï€/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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