Electrical Power system – II — Summer 2022

How are lines classified as short, medium and long transmission lines? What aspects you need to consider while modeling and carrying out performance analysis of these lines?

What are symmetrical components? With the help of vector diagram, explain the relationship between phase voltages and voltages of symmetrical components.

What is corona phenomena in transmission lines? Explain the factors affecting corona. State some of the methods to reduce corona. On which type of transmission line, corona losses would be more if we consider all other parameters to be same for 50 Hz and 60 Hz transmission line?

Differentiate between shunt faults and series faults. Give examples of the same.

Prove that velocity of transient travelling in underground cable is much less than overhead transmission line

Atransmission line having a length of 200 km has the following constants: Resistance/km = 0.15 Ω/phase, Reactance/km = 0.50 Ω/phase, Susceptance/km = 2 × 10-6 mhos. Voltage at the receiving end is 132 kV. If the transmission line is delivering 50 MVA at 0.8 pf lagging calculate (i) sending end voltage (ii) sending end current (iii) line efficiency. Use nominal T-method.

Using rigorous solution method, derive the expression for A,B,C,D constants for long transmission line

With the help of vector diagram, derive the approximate value of sending end voltage for short transmission line.

A 3-Ф, 50 Hz, 500 km long transmission line has the following line constants per phase per km uniformly distributed: r = 0.44 Ω, x = 0.9 Ω, g = 8 × 10-9 mhos, b = 5.06 × 10-6 mhos. Determine the line constants ‘A’ and ‘B’

Derive the equations for power flows (P , Q , P , Q ) through a R R S S transmission line

What is meant by X’’d, X’d and Xd? Which one has lowest value?

Discuss the criteria for selection of circuit breakers

For the network shown in figure-1, 3-phase fault occurs at point F. Determine the fault current and line voltage and 11 kV bus under fault conditions

Draw the zero sequence reactance diagram for the network shown in figure

Find the symmetrical currents for the given three phase currents: Ia = 10/00, Ib = 10/-900, Ic = 15/1350

Derive the expressions for positive, negative and zero sequence impedances of a fully transposed three phase balanced transmission line

Show that symmetrical component transformation is power invariant.

At a 220 kV bus of a power system it is given that three phase fault level is 4000 MVA. Neglecting resistance and shunt susceptances of the system, find the positive sequence driving reactance at the bus in ohms.

Derive the expression for fault current due to LLG fault at the generator terminals

State the disadvantages of corona

Explain over voltages generated due to arcing ground phenomena

Derive the expression for attenuation of a travelling wave

Which fault would be more severe at the terminals of a solidly grounded generator? Justify your answer

Explain the procedure for finding the centre and radius of receiving end power circle diagram

Derive the expression for co-efficient of reflection and refraction for a transmission line having surge impedance Zterminated by0 resistance R Fig 1 Fig