JNTU B.Tech III POWER SYSTEMS II Previous Question Paper (August/September - 2024 - R13)

What is the need of double circuit transmission line?

What are the advantages of bundled conductor?

Define the voltage regulation.

Define the surge impedance. Give its significance.

What is the effect of shunt capacitance at the terminal of a transmission line?

What are the effects of corona?

What are the types of insulators?

What are the main components of overhead lines?

What is meant by grading of cables?

What are the advantages of underground cables?

How do you classify the transmission lines? Discuss them.

Derive the formula for inductance for loop per meter of a two-wire transmission line using solid round conductors.

What is the method of images? Derive an expression for the capacitance per unit length of a 3-phase line completely transposed. What is the effect of earth on the capacitance of the line?

Calculate the capacitance per phase of a three phase, three wire system, when the conductors are arranged in a horizontal plane with spacing D12=D23=3.5m, and D13=7m. The conductors are transposed and each has a diameter of 2.0 cm.

Explain the effect of power factor on regulation and efficiency.

A three-phase line delivers 3600 kW at a p.f 0.8 lagging to a load. If the sending end voltage is 33 kV, determine (i) receiving end voltage (ii) line current (iii)transmission efficiency. The resistance and reactance of each conductor is 5.31 Ω and 5.54 Ω respectively.

Starting from first principles deduce expressions for ABCD constants of a long line in terms of its parameters.

A three- phase transmission line has the following data: Resistance of each conductor = 20 ohms; Inductive reactance per Phase = 40 ohms; capacitive susceptance to neutral = 0.0004 mho; Load at receiving end = 12500 kVA at 0.8 p.f. Lagging; voltage at receiving end = 66kV. Find regulation and efficiency of transmission using nominal T Method.

Discuss the phenomenon of wave reflection and refraction. Derive expression for reflection and refraction coefficients of a travelling wave.

A transmission line has an inductance of 0.93 H/km and a capacitance of 0.0078 μF/km. This overhead line is connected to an underground cable having an inductance of 0.155 mH/km and a capacitance of 0.187 μF/km. If a surge of crest 100 kV travels in the cable towards its junction with the line, find the surge transmitted along the line.

Discuss why receiving end voltage of an unloaded long line may be more than the sending end voltage.

A 132 kV line with 2 cm diameter is built so that corona takes place if the line voltage is 220 kV (r.m.s). If the value of potential gradient at which ionization occurs can be taken as 30 kV per cm(peak). Find the spacing between the conductors.

Explain why suspension insulators are preferred for high voltage transmission lines. What is a strain insulator and where it is used?

In a 3-unit string insulator, the joint to tower capacitance is 20% of the capacitance of each unit. By how much should the capacitance of the lowest unit be increased to get a string efficiency of 90%. The remaining two units are left unchanged.

What is a stringing chart? Explain clearly the procedure adopted for stringing the power conductors on the supports.

Derive the expression for sag and tension when the supports are at unequal heights.

What are all the insulating materials used in underground cables? Explain in detail about different kinds of insulating materials.

Describe with a neat sketch the construction of 3-core belted type cable. Discuss the limitations of such a cable.

Find expressions for capacitance, insulation resistance and dielectric stress of a single core cable.

The inner conductor of a concentric cable has a diameter of 5 cm, the diameter over the insulation being 9 cm. The cable is insulated with corresponding safe working stresses of 38 kV/cm and 26 kV/cm respectively. Calculate the radial thickness of each insulating layer and the safe working voltage of the cable.