These question papers have been obtained with the express permission of the Lecturer teaching the course for academic purposes.
ENUGU STATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ESUT
DEPARTMENT OF ELECTRICAL/ELECTRONICS ENGINEERING
SECOND SEMESTER EXAMINATION 2011/2012 SESSION
ELECTRICAL POWER SYSTEMS ANALYSIS. (EEE 616) PGD Class
TIME: 1Hr 30Min (Answer All Questions)
NB: IF you have not done any continuous assessment, write down what you have learnt in about 120 words first.
Basic Concepts
What is modeling? What is Symmetrical Components? Explain the difference between an active load and a passive load? What is a Phasor? What is Per Unit and what is it used for? How does a synchronous generator work? Develop the model of a Synchronous generator. Develop the model of a long line. Develop the model of a transformer. What is a Bus? What types of Buses are there in the Electrical Power System and what are their characteristics? What is Load Flow analysis? What is Stability Studies? What is State Estimation? What is Fault Analysis? What is the relationship between fault Analysis and Protection? Develop an expression for Symmetrical Component impedance for a three phase system. What are the parameters of a transmission line and what is their significance? What factors affect the resistance of a transmission line and how are they accounted for? Develop an expression for the inductance of a line.
Application
The Niger Delta region has developmental challenges. How would your knowledge of this course help to assist in the provision of sustainable electrical Power supply to the entire area considering the difficult terrain and the security challenges associated with the Niger Delta. How would you ensure that this in turn translates to a rapid economic growth, not only for the Niger Delta Region but for the entire country and the Sub-region. What is the Grid? What is an infinit bus? Explain the difference between a balanced fault and an unbalanced fault. What is the relevance of Electrical Power System Analysis in the Management of the Electrical Power System. What is a single line diagram?
Calculation
Derive an expression for Complex Power using Symmetrical Components. Compare this expression with the expression of Power using original phasors. Explain your work.How would you evaluate three phase complex power using these two expressions and compare your result. Explain your work; Hence:
Calculate the three phase complex power using the original phasors and the Symmetrical Components and compare the two results. Explain your work.
Given Vabc = Iabc =
Explain the procedure for calculating the Y-Bus Matrix. The transmission line in the figure below is 200km long and a 132kV line of the phase symmetric type. Calculate the Y Bus Matrix given that R = 0.075 Ω/km, ωL=0.435Ω/km, 1/ωC = 0.532MΩ/km. Calculate the Y Bus Matrix. Explain your work. What is Y Bus Matrix used for? What is the relevance of symmetrical Components in Fault Analysis?
ENUGU STATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ESUT
DEPARTMENT OF ELECTRICAL/ELECTRONICS ENGINEERING
SECOND SEMESTER EXAMINATION 2011/2012 SESSION
ADVANCED POWER ELECTRONICS AND DRIVES. (EEE 777) Masters Class
TIME: 1Hr 30Min (Answer All Questions)
NB: IF you have not done any continuous assessment, write down what you have learnt in about 120 words first.
Basic Concepts
What is Power Electronics all about? What is the relevance of thyristor in Power Electronics. What is the difference between a thyristor and a diode? How can a thyristor act as a switch? What is a switch? How does a thyristor work? What is the relevance of the analysis of step responses of R, RL, and RC circuits. Explain the behavior of an RL switched load circuit. What is the practical implication of this analysis? How does a Half Wave rectifier circuit work? How would you analyse the resultant waveform?
What is commutation? What types of commutation do we have? Explain any one and show how it can be achieved. What factors affect the conduction duration and the value of the output current of a controlled halfwave rectified current? Develop an expression for the output currents of a controlled half-wave Rectifier. What is the function of a freewheeling diode? What is the relevance of a heat sink in a power electronic device? What is the difference between an ideal diode and a practical diode? How does this difference manifest and how is it taken care of? What is the characteristic of an ideal diode? What is the relevance of fourier series in Power Electronics? What is the difference between a periodic waveform and a sinusoidal waveform? What aspects of Power Electronics study and devices do you know and what do you know about them? Why is it important to analyse Power Electronic circuits?
Application
What are the applications of Power Electronics you know? (List and explain any four of them.) What is the difference a controlled halfwave rectifier and an uncontrolled halfwave rectifier? How can a power electronic device act as a switch? Make a proposal to the Federal Republic of Nigeria on how a DC link can be constructed between the Congo Democratic Republic and Nigeria to evacuate Electrical Energy from a Hydro power plant situated at the Cong river to Nigeria? What are the merits and demerits of such a proposal? What are the technical requirements and challenges of such a proposal? Compare this proposal with the existing transmission link between Nigeria and the Niger republic. What are the characteristics of these links? How would this course of study assist you in your work? Design an inverter and explain how it works.
Calculation
How are harmonics accounted for in circuit analysis? Consider a factory for cement production and petrochemicals. There are lots of electric motors and drives. Some of these drives and machines require continuous operation and as a result require constant Electrical Power supply. It is proposed that they be inverter driven. What are the likely output waveforms of such a supply? How would the electrical circuit of this establishment be analysed bearing this in mind? What is turn off time?
In the Inverter circuit you designed, connect an ‘RLC’ series Load Circuit with the following parameters: R=0.7Ω, ωL=8Ω , 1/ωC =8Ω, V/2 = 24V, with continuous gating signals.
a) Sketch to scale the waveform of the output voltage vo, and current io, and the thyristor currents iQ1, iQ2, and the diode current iD1, and iD2, as well as the source currents and the thyristor voltage VAK1.
b) Show that the power delivered by the two sources is equal to the Power delivered to the Load circuit.
c) State whether this circuit will require forced commutation. Explain your work.
What factors affect the forced response of a circuit? What factors affect the natural response of a circuit? In what Power electronics circuit or device are you likely to encounter these responses and how would you ensure that the circuit performs optimally?
MBAH RAPHAEL. C.
ReplyDeleteESUT/2010/110324
ELECTRICAL AND ELECTRONICS ENGINEERING
TOPIC: WHAT I HAVE LEARNT SO FAR
UNDER FAULT ANALYSIS
I learnt the Definition of fault, types of fault, causes of fault and meaning of fault analysis.
Fault can be defined as the flow of a massive current through an improper path which could cause enormous equipment damage which will lead to interruption of power, personal injury or death.
Fault Analysis can be described as the process of evaluating the system voltages and currents various types of short circuit.
Fault; usually occur in power system due to insulation failure, flashover, physical change or human error. Fault can be caused by short circuit to earth or between live conductors or by broken conductors in one or more phases.
TYPES OF FAULTS
1. Balanced and
2. Unbalanced fault.
NAME: ALOR PASCHAL. A
ReplyDeleteDEPT: ELECTRCAL/ELECTRICAL ENGINEERING
REG NO.: ESUT/2012/137649
TITLE: POWER SYSTEM ANALYSIS
CODE: EEE554
WHAT I HAVE LEARNT
Load flow analysis: This is the study of power system to know the voltages at the various buses using the system configuration, loading at various buses, system topology and system parameters.
Types of load flow analysis
1. Newton Raphson iteration method.
2. Gauss Seidel iteration method.
Symmetrical components: These are set balanced phasors which can be used to represent or resolve an unbalanced system of ‘n’ related phasor into ‘n’ systems of balanced phasors. The symmetrical components have both length and angle between them equal.
Types of symmetrical components
1 Positive sequence components
2 Negative sequence components 3. Zero sequence components
Stability studies: this is the study of a system to know if a system will retain synchronism after perturbation or disturbance.
Types of stability studies
1. Dynamic
2. Transient
3. Steady state
Name: Ukemenam Anthony Chizoba
ReplyDeleteReg No: ESUT/2011/110446
Course Code: EEE554
The power system is either single phase or three phase. The phase is as a result of how the alternating current (AC) is produced. AC is produced from synchronous machine ie Generator. Electromagnetic force (EMF) is induced in the three windings placed symmetrically round the periphery of the stator of the synchronous machine, this induction takes place simultaneously but differentially depending on the level of flux linkage on various windings. This flux linkage depends on the magnitude and direction of the produced flux in the winding and arm reaction of the synchronous generator. These three induced voltages or EMF are then seperated from each other by a 120 electrical degrees, which is then identified as the three phases of the electrical power system.
A bus is a connection point in a power system, it can also be reffered to as a bus bar.
Grid system also can be reffered to as an infinite bus, which is a network of interconnected systems for effective transmission.
A power system can be correctly represented as;
1. Generation.
2. Transmission/Substransmission.
3. Distribution.
4. Load.