Anna University Chennai 2005-1st Sem B.E Electrical and Electronics Engineering VESTER EE339 - POWER SYSTEM ANALYSIS - Question Paper

ANNA UNIVERSITY :: CHENNAI – 600 025 MODEL ques. PAPER
VI - SEMESTER
B.E. ELECTRICAL AND ELECTRONICS ENGINEERING
EE339 - POWER SYSTEM ANALYSIS
Time: 3hrs Max Marks: 100
ans all ques.
PART – A (10 x two = 20 Marks)
1. What is the need for system analysis in planning and operation of power
system?
2. How are the base values chosen in per unit representation of a power system?
3. Draw the ? equivalent circuit of a transformer with off-nominal tap ratio t and
admittance y.
4. describe bus incidence matrix.
5. Mention 2 objectives of short circuit analysis.
6. Draw the zero sequence network of a star connected generator with zero
sequence impedance Zgo when the neutral is grounded through an impedance Zn.
7. elaborate the 3 classes of buses of a power system used in power flow
analysis? elaborate the volumes to be specified and to be calculated for every
class during power flow solution?
8. Compare Gauss-Seidel method and Newton – Raphson method with respect to
number of iterations taken for convergence and memory requirement.
9. describe critical clearing time.
10. Write the power-angle formula of a synchronous machine connected to an
infinite bus and also the expression for maximum power transferable to the bus.
PART B (5 x 16 = 80 Marks)
11. find the per unit impedance (reactance) diagram of the power system shown
in Fig.Q.11
T1 T2
G1 T.L G2
Xn1 Xn2
Fig. Q.11
Generator No.1: 20 MVA, 10.5 KV, X’’ = 1.4 ohms, Xn1= 0.5 ohm
Generator No.2: 10 MVA, 6.6 KV, X”= 1.2 ohms, Xn2 = 0.5 ohm
Transformer T1 (3 phase): 10 MVA, 33/11 kV, X = 15.2 ohms per phase on
high tension side.
Transformer T2 (3 phase) : 10 MVA, 33/6.2 kV, X= 16 ohms per phase on high
tension side.
Transmission line: 22.5 ohms / phase.
select a common base of 20 MVA
12.a) Determine Z bus using bus impedance matrix building algorithm by adding the
lines as per increasing element number. The reactance diagram of the system is
shown in Fig. Q.12(a).
1 ELEMENT two 2 ELEMENT four 3
j0.25 j0.05
ELEMENT one ELEMENT three j1.25
j1.0
Ref bus
Fig Q.12 (a)
(OR)
12.b) discuss the modelling of Generator, Load and Transmission line for short
circuit, power flow and stability studies.
13.a) Derive the formula for fault current, fault-bus voltages and current through the
lines for a three phase symmetrical fault at a bus in a power system using Z bus.
State the assumptions made in the derivation.
(OR)
13.b) A single line to ground fault occurs on bus four of the system shown in Figure.
Q.13(b)
(i) Draw the sequence networks.
(ii) calculate the fault current
G1 one two three four G2
T1 T2
Xn
Xn
Fig Q.13 (b)
Generator one & two : 100 MVA, 20kV with X1 = X2 = 20%, X0 = 4%, Xn = 5%
Transformer one & two : 100 MVA, 20kV/345kV. X leakage = 8% on 100 MVA.
Transmission line: X1 = X2 =15% and X0 =50% on a base of 100 MVA, 20kV
14.a) discuss clearly the algorithmic steps for solving load flow equations using
Newton – Raphson method (polar form) when the system contains all kinds of
buses. presume that the generators at the P-V buses have enormous Q limits and
hence Q limits need not be checked.
(OR)
14.b) The system data for a load flow issue are provided in Table one and Table 2.
(i) calculate Y bus
(ii) Determine bus voltages at the end of first iteration by Gauss-Seidel method.
Take acceleration factor as 1.6.
Bus Code of Lines Admittance (p.u)
1-2 2-j8
1-3 1-j4
2-3 0.6-j2.6
TABLE – one Line Data
Bud Code P Demand
in p.u
Q Demand
in p.u
V, p.u Remarks
1 - - 1.06?0 Slack
2 0.5 0.2 - PQ
3 0.4 0.3 - PQ
TABLE – two Bus Data
15.a)i) Write the swing formula describing the rotor dynamics of a synchronous
machine connected to infinite bus through a double circuit transmission line.
ii) discuss the step-wise procedure of determining the swing curve of the above
system using replaced Euler’s method.
(OR)
15.b) In the system shown in Fig, Q. 15(b) a three phase fault occurs at point P closer to
bus 2.
1 L1 2
1 L2 P 2
| E’ | = 1.2 p.u
Fig. Q.15 (b)
obtain the critical clearing angle for clearing the fault with simultaneous opening of
the breakers one & 2. The reactance values of the different components are Xg = 0.15
p.u Xtr=0.1 p.u, XL1 = 0.5 p.u, XL2 = 0.4 p.u. The generator is delivering 1.0 p.u
power at the instant preceding the fault.
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Earning:   Approval pending.