Part I
Choose the best answer
1. In pure Resistive circuit the angle between Voltage and current is
(a) Infinite
(b) Zero
(c) 900 lag (d) 900 lead
2. A control system is stable if and only if
(a)
All closed loop poles lie in the right-half s plane.
(b)
All closed loop poles lie in the left-half s plane.
(c)
All closed loop zeros lie in the right-half s plane.
(d)
All closed loop zeros lie in the right-half s plane.
3. Which Element can allow the conduction of electric current in both directions?
(a) Resistance (b) capacitance (c) a & b
(d) diode
4. Which one of the following is not true about transient response of the system
(a) The total time it takes to achieve the output for the first time
(b) The time that it takes to settle to the final value
(c) Whether or not the output oscillates about the final value
(d) Whether or not any error exists between the desired and the actual value
5. What do you think about the system stability of the transfer function
(a) the system is unstable
𝑆+2
𝑠2 −1
(b) The system is marginally stable (c) The system is stable
(d) all
6. _______ is an element within the system itself, or external to the system, and it controls the
plant or the process.
(a) controller (b) input (c) output
(d) Plant (e) Disturbance
7. A 3phase 4 wire system is commonly used on
a) Primary transmission
b) Secondary transmission
c) Primary distribution
d) Secondary distribution
8. For which of the following equipment current rating is not necessary
a) Circuit breaker
b) Isolator
c) Load break switch
d) Circuit breaker and load break switch
9. For transmission of power over a distance of 200KM the transmission voltage should be
a) 132kV b) 66kV c) 33kV
d) 15kV
10. The two windings of a transformer is
(a) Conductively linked.
(c) Not linked at all.
(b) Inductively linked.
(d) Electrically linked
11. If a transformer primary is energized from a square wave voltage source, its output voltage
will be
(a) A square wave.
(b) A sine wave.
(c) A triangular wave.
(d) A pulse wave.
12. As the voltage of transmission line increases, the volume of conductor
(a) increases.
(c) decreases.
(b) does not change.
(d) increases proportionately.
13. The boundary of the protective zone is determined by the
(a) Location of CT
(b) sensitivity of relay used
(c) Location of PT
(d) None of these
14. What is skin effect in an electric transmission line conductors
(a) The tendency of high-frequency alternating current to distribute near the surface of a
conductor
(b) An electrical discharge accompanied by ionization of surrounding atmosphere of the
conductor
(c) The tendency of high-frequency alternating current to distribute internally of a
conductor
(d) None
15. Most electric power consumers (customers) are penalized by Ethiopia electric utility (EEU)
due to :
(a) The consumption of active power
(b)
The consumption of reactive power
(c) The consumption of apparent power
(d) All of the above (e). None
16. One of the following describes characteristics of low voltage transmission line
(a) The capacitance effects are small and hence can be neglected
(b) The capacitance effects are taken into account.
(c) All parameters of the transmission line are considered
(d) All of the above
(e) None
17. The relative speed between the magnetic fields of stator and rotor under steady state
operation is zero for a
(a) DC machine.
(c)
(b) 3 phase induction machine.
Synchronous machine.
(d) single phase induction machine.
(e) All of the above
18. In a 3-phase synchronous motor
(a) The speed of stator MMF is always more than that of rotor MMF.
(b) The speed of stator MMF is always less than that of rotor MMF.
(c) The speed of stator MMF is synchronous speed while that of rotor MMF is zero.
(d) Rotor and stator MMF are stationary with respect to each other.
19. If you have a DC derive motor and your supply from the utility is an AC supply which of the
following power electronic devices are more suitable for your device supply.
(a) Rectifier (b) Inverter (c) Cyclo-converter (d) Chopper
20. Which one the following is true
a) BJT is a current controlled device whereas JFET is a voltage controlled device
b) The conduction level of BJT is a function of two charge i.e. electrons and holes
c) The conduction level of JFET is depends only on electrons or holes
d) All
21. The average DC output of the half wave rectifier is
(a)
𝑉𝑚
𝜋
(b) 2
𝑉𝑚
𝜋
(c)
𝑉𝑚
√2
(d)
𝑉𝑚
2
22. Which of the following passive element
a) Capacitance b) ideal current source
c) ideal voltage source
d) all
23. The total current flow in the circuit given in in the figure below is given by:
(a)
𝑉
𝑅
b)
𝑉
𝑅+𝑅1
c) ∞
d) 0
24. Identify the symbol and its name match incorrectly
25. If an intrinsic semiconductor is doped with the pentavalent atom, the pentavalent atom is
a) donor
b) acceptor C a and b
Part II:
Explain the following questions briefly and clearly
1. Compare and contrast open loop and closed loop control system
2. Write the advantageous and disadvantageous of HVDC over HVAC transmission lines
3. Write down the similarity and difference of instrument transformer and power
transformer.
4. List down at least four types of cooling systems in transformers.
5. List and compare the conventional controllers
6. Write down at least three types of reactive power compensator devices
7. What is the difference and similarities between circuit breakers and relay?
8. Draw and explain the main power system structures
9. If you are order to design PID controller for any plant what specification you used?
10. The utility A is going to design transmission line within high voltage X _KV values and
utility B is design the same transmission line but doubling the value of high voltage (X).
Depending on the above explanation determine the following
a) The ratio of the resistance of utilities
b) Voltage drop of utility A in terms of utility B
c) Power loss of utility B in terms of utility A
d) Which utility is efficient? Why?