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Wednesday, 29 April 2015

Q-Bank-PSA&S-150902_All Chapter_5th EE

Ch:-1 Current and Voltage Relations on a Transmission Line:

1.      From first principles, derive the A, B, C and D constants of a long transmission line.
2.      Derive the equation for active and reactive powers flow in transmitted to load over a long line.
3.      Starting from the first principles, show that surges behave as travelling waves. Find expressions for   surge impedance and wave velocity.

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

5.      Derive expressions of voltage phasor and current phasor at any point of a long transmission line as function of distance x from receiving end in terms of distributed parameters of the line, voltage phasor VR (voltage at receiving end) and current phasor IR (current at receiving end). State difference between characteristic impedance and surge impedance of the line.

6.      What is an equivalent π and equivalent T circuit of a long transmission line?

7.      Derive the ABCD constants for medium transmission line using Nominal Π representation. Also write the expressions for voltage regulation and efficiency for the same line.


Ch:-2 System Modeling:
8.      What is importance of one line diagram of a power system? How it is drawn?

9.      Explain one-line diagram in brief. What is P. U. system? Write advantages of per unit system.
10.  Explain the Equivalent Circuit model of Synchronous machine. From the first principal, derive Vt = Ef – Ia (Ra+ jXs) Where Xs = Xar + Xl. Also draw the equivalent circuit diagram.

11.  With the help of neat phasor diagram, explain the operation of synchronous generator for different field excitation. 


Ch:-3 Symmetrical Three-Phase Faults:
12.  Draw the waveforms for fault current for a 3-phase fault on alternator     terminals.    Explain the sub-transient, transient and steady state reactance. What is their significance in fault calculations?
13.  Explain the importance of bus impedance matrix in fault calculation.
14.  How the circuit breaker is selected for any particular location. 

Ch:-4 Symmetrical Components:.

15.  Write a brief note on phase shift of symmetrical components in Y-Δ transformer banks.

16.  Write a note on zero sequence networks in brief.
17.  Derive the expressions of positive, negative and zero sequence voltage components in terms of given set of unbalance voltage phasors Va, Vb and Vc. Also prove that the transformation used is power invariant.

Ch:-5 Unsymmetrical Faults:
18.   Using appropriate interconnection of sequence networks, derive the equation for a line to line fault in a power system with a fault impedance of f Z
19.  Justify the following statement:
“For a fault at alternator terminals, a single line to ground fault is generally more severe than a 3-ph fault whereas for faults on transmission lines, a 3-ph fault is more severe than other faults.”
20.  Explain how fault current can be calculated when L-G fault occur through a fault impedance Zf.
21.  Draw a general circuit which can be used to determine zero sequence network of a two-winding transformer. Using this circuit, draw the zero sequence networks for (i) delta-star transformer with star point grounded. (ii) delta-delta transformer. (iii) star-star transformer with star point grounded.

22.  Derive an expression for the fault current for a double-line fault as an unloaded generator.

Ch:-6 Corona:
23.  Describe the phenomena of corona in brief. What are the factors and conditions affecting corona loss?

24.  Explain the advantage, disadvantage and method of reducing  phenomena of corona. 

Ch:-7 Neutral Grounding:
25.  What are the various methods of neutral grounding? Explain all. (resonant grounding)
26.  Explain neutral grounding using phasor diagrams.. Give Advantage of neutral grounding.
  

Ch:-8 Transients in Power Systems:
27.  Explain single and double frequency transient.
28.  Write a brief note on capacitance switching.
29.  Discuss the behavior of a travelling wave when it reaches the end of (i) open circuited (ii)short circuited transmission line. Draw diagrams to show voltage and current on the line before and after the wave reaches at the end.

    Combination

30. Give reasons for following:
1.      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.
2. A travelling wave suffers reflection when it reaches discontinuity.
3. The disruptive critical voltage is less than visual critical voltage.








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Tuesday, 7 April 2015

Q-Bank_All Chapter_TOE-160906_6th Electrical

Ch: 1 Vector Analysis
1)
Define: 1) Vector, 2) Scalar, 3) Unit Vector, 4) Position Vector, 5) Scalar projection, 6) Vector Projection.
2)
Explain dot product and cross product of two vectors.
3)
Explain unit vectors of Cartesian, Cylindrical and Spherical co-ordinate systems.
4)
Find expression for different length, area and volume for cylindrical system.
5)
Given the point A(x=5,y=4,z=3) and B (r=6, θ=450 Φ=100) find : 1)The spherical coordinate A , 2) The Cartesian coordinate of B, 3) The Distance from A to B.
6)
Example of different co-ordinate conversation system.
Given points A( x = 5, y = 1, z = -4) and B(ρ= 3, Φ = -30, z = 5), find a unit vector in cylindrical  ordinates at point B directed towards point A.
7)
Obtain the spherical co-ordinates of 2 āx+3 āy+4 āz at the point P(x= 4, y =1, z = 3)

 Ch : 2 Electrostatic Field in free Space
Ø Coulomb’s law and Electric field intensity
8)
Describe coulomb’s law and Electric field intensity.
9)
Define electric field intensity. Obtain the expression for the electric field intensity at a point which is at a distance of R from a point charge Q.
10)
Derive expression of electric field intensity due to a uniform line charge over z-axis
Having  a charge density of C/m.
11)
The finite sheet 0 ≤ x≤ 1, 0≤y≤1 on the z = 0 plane has a charge density ρs = xy (x2 + y2 + 25)^3/2 nC/m2. Find: 1) The total charge on the sheet, 2) The electric field at (0, 0, 5),
12)
Derive the expression for total electric field intensity due to infinite surface charge distribution in free space.
13)
Find Ē at the origin if the following charge distributions are present in free space : a) point charge 12 nC at P (2,0,6), b) uniform line charge density 3nC/m at x = - 2, y = 3, c) uniform surface charge density 0.2 nC/m2 at x = 2.
Ø Electric flux density, the Gauss’s law and Divergence
14)
State and prove the Gauss’s law. Also state the conditions to be satisfied by the special Gaussian surfaces.
15)
Application of gauss’s law-To find electric flux density due to a uniform line charge.
16)
Define divergence and its physical significance with example.
17)
D=2y2z2 āx +3xy2z2 āy +2xyz āz pc/m2in free space. Find (a) Total flux passing through the surface x=2,  0 ≤  y ≤  4, 0 ≤ z ≤ 3in a direction away from the origin , (b) The total charge contained in incremental sphere of a radius 1µm cantered at p (5,5,5)  
18)
Explain Gauss’s law applied to differential volume element with usual expression.
Ø Energy and Potential
19)
Explain potential and potential gradient. Derive relationship between potential and electric field intensity.
20)
Explain electrical dipole. Also derive expression of E due to an electric dipole.
21)
An electrical dipole located at the origin in free space has a moment
P = 2 āx+3 āy+4 āz nC. Find (A) find V at PA (1,2,3).
22)

Write short note: Electrostatic boundary conditions between perfect dielectrics.
23)
Given the potential field,V= 2x2+3zy2, and a point P(2, 5, 1), find following at point P: (1) the potential V, (2) the electric field electric flux density D, and (5) the volume charge density .

Ch : 3 Electrical Field in material Space and Boundary Condition
Ø Current,  Conductor
24)
Derive the relation between I and J and explain the continuity equation of steady electric current in integral form and point form.
Ø Dielectrics and Capacitance
25)
Write short note: Electrostatic boundary conditions between perfect dielectrics.
Ø Poisson’s and Laplace’s equation.
26)
Derive Poisson’s and Laplace’s equation.

Ch 4 : Steady Magnetic Field
27)
State and explain Biot-Savart’s law.
28)
Write short note on Stoke’s theorem.

Ch : 5 Magnetic Forces and Materials and Inductance
29)
State and Explain Lorentz force equation on charge particle. Also explain concept of magnetic torque.
30)
Write short-note on ‘ magnetic materials’
31)
State and Explain Ampere circuital law.

Ch : 6 Time Varying Fields and Maxwell’s Equations
32)
State Maxwell’s equations in point form and explain physical significance of the equations.
33)
Write and explain differential and integral forms of Maxwell’s equations.

Ch : 7 Analytical and Numerical techniques
34)
Explain briefly finite element method. Also state the advantages and disadvantages of finite element method.
35)
Write a short note on advantages and applications of numerical techniques in engineering.