Electrical Power system – II — Summer 2023

What is importance of receiving end power circle diagram? Explain the steps of constructing it.

Write a brief note on capacitance switching. Derive the ABCD constants for medium transmission line using

Nominal Trepresentation. Also write the expressions for voltage regulation and efficiency for the same line.

Explain the sub-transient, transient, and steady state reactance.

What are series reactors? How are they classified. Distinguish between symmetrical and unsymmetrical faults.

07 How symmetrical faults are analyzed?

Explain the Equivalent Circuit model of Synchronous machine?

07 Also draw the equivalent circuit diagram. Give reason: The analysis of unsymmetrical faults can be more

easily done with the help of symmetrical components than by a direct solution of the unbalanced circuit. Show that symmetrical component transformation is power

04 invariant. Explain the zero-sequence impedance of transformer for various

07 connections.

Why does a generator produce only positive sequence voltage?

03 Discuss. State the frequency of zero sequence phasors. Describe the

04 applications of symmetrical components. State the frequency of zero sequence phasors. Describe the

07 applications of symmetrical components. Give reason: for a fault at alternator terminals, a single line to

03 ground fault is generally more severe than a 3-phase fault. derive the equation for a line-to-line fault in a power system with

04 fault impedance of Z. f Explain traveling and reflecting waves on transmission line with

07 open end at the receiving. OR1

Write a brief note on overvoltage due to arcing ground. Give reason: Atravelling wave suffers reflection when it reaches

04 discontinuity. Explain the phenomena of corona. Also discuss the measures

07 taken to control corona in EHVAC transmission lines.

Write short note on radio interference. How can corona loss be calculated? What is the meaning of

04 roughness factor? A 3-phase. 50-Hz overhead transmission line 100 km long has the following constants. Resistance/km/phase = 0.1 Ώ Inductive reactance/km/phase = 0.2 Ώ Capacitive susceptance/km/phase =

0.04 × 10 -4 siemen Determine (i) the sending end current (ii) sending end voltage (iii) sending end power factor and (iv) transmission efficiency when supplying a balance load of 10,000 kW at 66 kV p.f 0.8 lagging . Use nominal Tmethod.

The currents in three phase unbalanced system are IR = (12 + j6) A, IY = (12 - j12) A, IB = (-15 + j10) A. The phase sequence is

03 RYB. Calculate, positive, negative and zero sequence components of currents. Find the disruptive critical voltage and visual corona voltage (local as well as general corona) for a 3-phase 220 kV line consisting of 22.26 mm diameter conductors spaced in a 6 m delta

configuration. The following data can be assumed: Temperature 25° C, pressure 73 cm of mercury, surface factor 0.84, irregularity factor for local corona 0.72, and irregularity factor for general (decided) corona 0.82. Starting from the first principles, show that surges behave as