MORE QUESTION PAPERS

THESE QUESTION PAPERS WERE 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 INTRODUCTION TO ELECTRICAL POWER SYSTEMS ENGINEERING. (EEE 352) 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 renewable energy sources? How does a transformer work? What is Load Duration curve? What factors affect the economic operation of Electrical Power Plants? Explain any two of these factors. How would you improve the thermodynamic efficiency of a Thermal Power Station? What is single line diagram? What is Per Unit System? Derive an expression for the efficiency of a transformer. How would determine the parameters of a transformer? Describe the relevant experiments and derive the relevant equations for this purpose. What is an autotransformer? How does it work and what can it be used for? Derive an equation for determining the winding impedances of a three winding transformer, using measurements from experimental values. Describe and explain your work. What types of lines are there in the Electrical Power System? Explain the differences between these types of lines. Derive a model and an expression for the medium line for Electrical Power System Analysis. What are line parameters? Explain any two of them.

Application

You are responsible for the establishment of a new Teaching Hospital in your state. What would you do to ensure that this hospital has steady Electrical Power supply? What would you do to ensure that if the hospital is located outside the town, support services provided by other utility services would be properly taken care of and that the Electrical Power needs of the entire medical complex and the host community is adequately met? Explain how your knowledge of this course would assist you in your work. What is Load Flow Analysis and what is it used for? What is fault Analysis and why is it carried out? What is Stability Studies and what types of Stability Studies are there? What is the relevance of State Estimation in Electric Power provision?

Calculations

A single phase transformer has 1000 turns on the primary winding and 200 turns on the secondary. Winding resistances are r1 = 1.0 Ω and r2 = 0.105 Ω Leakage reactances are x1 = 5.0 Ω and x2 = 0.25 Ω. The resistance load Z2 is 10 Ω. If applied voltage at the terminals of the primary winding is 1000V, find V2 and the voltage regulation. Neglect magnetizing Current. The results of the open-circuit and short circuit tests of a 220/110 V 10kVA single phase transformer are as follows Primary Secondary Open Circuit Test Open Circuit 100V , 5A, 154W Short Circuit Test 18V, 45.2A, 240W Short - Circuit Determine the parameters of the approximate equivalent circuit of the transformer and express these quantities in per unit values. The three phase rating of a three winding transformer are Primary Υ Connected 55kV 10MVA Secondary Υ Connected 12.1kV, 7MVA Tertiary Δ 2.2kV, 2.5MVA Neglecting resistance, leakage impedances are, Zps = 5% on 10MVA, 55kV base; Zpt = 8% on 10MVA, 55kV base; Zst = 7% on 7MVA, 12.1kV base Find the per Unit impedance of the star connected equivalent circuit for a base of 10MVA, 55kV in the primary. If N1 =1000 and N2=200 in a transformer. Draw the equivalent circuit of the transformer. If V1 = 1000/0o and I1 = 4/-45oA with impedance Z2 connected across the winding 2. Find V2, I2 and Z2 and the impedance Z’2 which is defined as the value of Z2 referred to the primary side of the transformer.