BAZE University, Abuja
Faculty of Engineering
Level 500, Trimester 3 (23A), 2023 Examinations
Power Systems Engineering
(EEE507)
Instructions: Attempt any four (4) questions; duration is two and a half (2.5) hours; The University’s Rules
and Regulations guiding Examinations are hereby applied.
QUESTION ONE
a. What are the cost components associated with power generation system? Write the equation, relating
the components. [6 marks]
b. A distribution transformer costs N 2,00,000 and has a useful life of 20 years. If the salvage value is
N10,000 and rate of annual compound interest is 8%, calculate the amount to be saved annually for
replacement of the transformer after the end of 20 years by sinking fund method. [9 marks]
QUESTION TWO
a: With the aid of sketch diagram, briefly explain peak and base periods of a typical load duration curve.
[4 marks]
b: A proposed station has the following daily load cycle as shown in Table 2b
Table 2b
Time, Hrs
Load, MW
6-8
20
8 - 11
40
11 - 16
50
16 - 19
35
19 - 22
70
22 - 24
40
24 - 6
20
Draw the load curve determine the load factor from the curve. [11 marks]
QUESTION THREE
Give the formula for evaluation of base Current, Ib, and base impedance, Zb, of a three phase system.
[5 marks]
b. The fuel costs of a two-unit power plant are given as follows:
𝐶1 = 100 + 2𝑃1 + 0.005𝑃12
𝐶2 = 200 + 2𝑃2 + 0.01𝑃22
Where P1 and P2 are in MW. The plant supplies a load of 450 MW. Find economic load scheduling of the
units and incremental fuel cost. Neglect losses. [10 marks]
QUESTION FOUR
a: What are the information usually obtained from load flow study?
[5 marks]
b: The Maximum Weekly Demand on a new injection substation are tabulated in table 4b
Week
1
2
3
4
5
Maximum Demand, in kVA
200
150
220
210
140
Determine the forecast of maximum demand for the sixth week, using straight line method. [10 marks]
QUESTION FIVE
a: What is meant by symmetrical fault in a typical electric power system? [3 marks]
b. Determine the Ybus for the 4-bus system in fig.Q5b. The line series impedances are as tabulated (in table
Q5b). neglect the shunt capacitances of the lines.
Fig. Q5b
Line (bus to bus)
Impedance, p.u.
Table Q5b
1-2
1-3
1-4
2-3
3-4
0.25+j1.0 0.2+j0.8 0.3+j1.2 0.2+j0.8 0.15+j0.6
[12 marks]
QUESTION SIX
a. Define Power system stability. [4 marks]
b. A two-pole 60Hz, 60MVA generator has a moment of inertia of 9x103 kg-m2. Calculate: (a) The kinetic
energy in MJ at rated speed.
(b) The inertia constants: angular momentum, M and per unit inertia constant, H.
(c) Inertia constant on 50MVA base.
[11 marks]