EE6501 Power system analysis, Third year, Department of Electrical and Electronics Engineering, Model Exam Questions.

Answer ALL Questions
Part A (5 x 2 = 10 Marks)
1.      What is single line diagram?
2.      Define per unit value
3.      What is the need for load flow study?
4.      When it generated bus treated as load bus?

5.      What is Jacobian matrix?
6.      What is direct axis reactance?
7.      What is a slack bus?
8.      What is the sequence operator?
9.      How is the power system stability classified?
10.  Write the power angle equation?
PartB(5x16=80 Marks)
11.  (a)  Draw the reactance diagram for the power system shown in Fig.1. Neglect resistance & use a base of 50 MVA & 13.8 KV on generator G1.
Determine the new value of per unit reactance of G1, T1, Transmission line 1, Transmission line 2, G2, T2, G3 and T3
Or
(b) Form Ybus of the test system shown in Fig.2 using singular transformation method. The impedance data is given in Table 1. Take (1) as reference node
12.  (a) The system data for a load flow solution are given in Table 2 and 3. Determine the voltages at the end of the first iteration using the Gauss Seidel method. Take 1=1.6
Table 2: line admittances
Bus code
Admittance
1-2
2-j8.0
1-3
1-j4.0
2-3
0.666-j2.664
2-4
1-j4.0
3-4
2-j8.0
Table 3: Schedule of active and reactive powers
Bus code
P in p.u
Q in p.u
V in p.u
Remarks
1
-
-
1.06
Slack
2
0.5
0.2
1+j0.0
PQ
3
0.4
0.3
1+j0.0
PQ
4
0.3
0.1
1+j0.0
PQ
Or
(b) Draw and explain the step by step procedure of load flow solution for the Gauss Seidel
method when PV buses are present
13.  (a) Generator G1 and G2 are identical and rated 11 kv, 20MVA and have a transient reactance of 0.25 p.u at own MVA base. The transformer T1 and T2 are also identical and are rated 11/66 kv, 5 MVA and have a reactance of 0.06 p.u to their own MVA base. A 50 km long transmission line is connected between the two generators. Calculate three phase fault current, when fault occurs at middle of the line as shown in Fig.        (16)
Or
(b) Explain symmetrical fault analysis using Z-bus matrix with neat flow chart                (16)
14.   (a) Derive the expression for the three phase power in terms of symmetrical components.     (16)
Or
(b) A 30 MVA, 11KV, three phase synchronous generator has a direct sub transient reactance of 0.25 p.u. The negative and zero sequence reactance are 0.35 and 0.1 p.u respectively. The neutral of the generator is solidly grounded. Determine the sub transient current in the generator and the line to line voltages for sub transient conditions when a single line to ground fault occurs at the generator terminals with the generator operating unloaded at rated voltage.                                         (16)
15. (a) Derive the expression for swing equation.                                                              (16)
Or
(b) Derive the expression for the critical clearing angle and clearing time                         (16)