Transmission Line Efficiency Formula Quiz and Flashcards

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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?

1.2 pu 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?

series capacitor Signup and view all the answers

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

$\frac{2\pi}{b}$ Signup and view all the answers

What is the efficiency of the transmission line?

80% Signup and view all the answers

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

Shunt capacitor Signup and view all the answers

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

Short transmission lines Signup and view all the answers

How can Ferranti effect be compensated?

Both a and b Signup and view all the answers

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

Shunt reactor 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?

$30°$ Signup and view all the answers

What type of impedance does an overhead transmission line have?

400 Ω – 600 Ω Signup and view all the answers

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

Head of water 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?

$s=WL^2/8T$ 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?

468 kg/m Signup and view all the answers

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

Head of water and Specific weight of water Signup and view all the answers

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

$√(C/L)$ 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?

Increases but not double 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?

Total negative VAR at sending end and zero VAR at receiving end Signup and view all the answers

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

Reduce the fault level Signup and view all the answers

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

Series RL circuit Signup and view all the answers

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

Is independent of the size of conductor and constant Signup and view all the answers

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

The switching voltage Signup and view all the answers

What is one of the advantages of higher transmission voltage?

Increased power transfer capability of the transmission line Signup and view all the answers

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

Parallel transmission lines Signup and view all the answers

What is one of the objectives of a power system?

Supplying rated voltage and frequency to consumers Signup and view all the answers

In an EHV system, why is shunt compensation applied?

To improve the stability Signup and view all the answers

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

Exists in the lines on the delta side Signup and view all the answers

Which matrix reveals the topology of a power system network?

Bus incidence matrix 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.

Transmission Line Efficiency, Power Factor, and Ferranti Effect Quiz

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