JNTU B.Tech III POWER SYSTEMS II Previous Question Paper (March - 2024 - R16)

Derive the inductance of 2-wire transmission line.

In a 3-phase transmission line the three conductors are placed at the corners of a triangle of sides 1.5m, 3m, and 2.6m respectively. If the diameter of each conductor is 1.4 cm and the conductors are regularly transposed, calculate the inductance/phase/km length of the line.

Derive the expression for capacitance of three phase transmission line with asymmetrical spacing.

Three conductors of a three phase transmission line are arranged in a horizontal plane and are 4 meters apart. The diameter of each conductor is 2.4 cm. Find the inductance per kilometer of each conductor. Assume the load is balanced and the phase sequence as R, Y, B. Find the average inductance per phase for the regularly transposed line.

Explain the effect of power factor on the regulation of the short transmission line.

A single phase overhead transmission line is delivering 600 kVA load at 2 kV. Its resistance and reactance are 0.18 ohm and 0.36 ohm per phase. Determine the voltage regulation if the load power factor is i) 0.8 P.F lag ii) 0.8 P.F lead.

Explain the concepts of incident, reflected and refracted waves in the transmission lines.

A 3 phase, 50Hz, 100km long transmission line delivers a load of 20000KW at 110KV at 0.9 power factor lagging. The copper conductors of the line are 1.2 cm in diameter and are spaced equilaterally, so that the distance between them is 2 m. Using nominal π method, calculate the sending end voltage, current, power factor, regulation and efficiency of the line. Neglect the leakage.

Discuss the propagation of surges in transmission lines.

Find the disruptive critical voltage and visual corona voltage (local corona as well as general corona) for a 3 phase 220 kV line consisting of 22.26 mm diameter conductors spaced in a 6 meters delta configuration. The following data can be considered. Temperature 250 C, Pressure 73 cm of mercury, surface factor 0.84, irregularity factor for local corona 0.72, irregularity factor for general corona 0.82 m.

Explain the effect of radio interference on the performance of transmission lines.

Derive the expressions for reflected voltage and current waves, when the transmission line is terminated by the capacitive load.

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

Each line of a three phase system is suspended by a string of 3 identical insulators of self-capacitance C farad. The shunt capacitance of the connecting metal work of each insulator is 0.3C to earth and 0.2C to line. Calculate the string efficiency of the system if the guard ring increases the capacitance to the line of the metal work of the lowest insulator to 0.35C.

Derive the expression for the Sag in vertical plane when the conductor is covering ice and wind pressure.

For a overhead line span length is 180m, difference in levels of supports is 7m, conductor diameter 2cm, weight per unit length of conductor 2 kg and wind pressure of 45 kg/m2 of projected area. If the maximum tensile strength of the conductor is 4500 kg/cm2 and safety factor 5, calculate the sag.

With neat sketch, explain about construction of underground cable.

A 3-phase 66 kV single-core lead sheathed cable has a conductor of 2 cm diameter and two layers of different materials each 1cm thick. The relative permittivity are 5(inner) and 3(outer). Calculate the maximum stress in the two dielectrics.

What is meant by grading of cables? Explain why and how the grading of cables is done?

The inner and outer diameter of a cable are 3.5 cm and 9 cm respectively. The cable is insulated with two materials having permittivities of 6 and 4 respectively, with corresponding stresses of 40 kV/cm and 30 kV/cm. Calculate the radial thickness of each insulator layer and safe working voltage of the cable.