EEET 4057 Power System Analysis

Instructions to students

Assignment must be typed in word processor (images must be screen captures, not photographs)

Handwritten or scanned submissions will not be accepted or graded

This is a group assignment and students should work on this assignment either individually or in groups of maximum of 3 students

Only collaboration among students in the same group is allowed

Collaboration among students from different groups is not allowed and will be treated as  academic misconduct

Each question carries 100 marks with sub-question weights indicated in the text in [red]

Document all your work to support your answers and make sure you use the correct units

Please submit only one copy of the assignment per group as PDF through learnonline

Q1. Two balanced 3?phase loads are connected in parallel and supplied by a balanced, three?phase 380Vrms source. One load draws 9kW at 0.7 power factor lagging and the other draws 7kVA at 0.9 power factor leading. (f=50Hz)

(a) Draw the power triangle for each load [10+10] and for the combined (total) load
(b) Determine the power factor of the total load
(c) Determine the magnitude of the line current from the source
(d) Δ?connected capacitors are now installed in parallel with the combined load. What value of capacitive reactance is needed in each leg of the Δ to make the source power factor equal to unity?
(e) Calculate the magnitude of the current in each capacitor [5] and the line current [5] from the source after the Δ?connected capacitors have been installed
(f) Now the connection to one of the capacitors is lost due to a fault. Determine the total 3?phase power supplied to the load [5], the line currents [5] and the neutral current [5]
(g) Use Multisim to check your results in (c) [10], (e) [5+5] and (f) [5+5] (Multisim screenshots need to be provided showing your model and ammeter readings matching your calculation results) EEET 4057 Power System Analysis by Sasha Jakovljevic EEET 4057 Power System Analysis 2019 – Assignment #1: Numerical Problems 2

Q2. Given are phase to neutral voltages of unbalanced 3-phase source:
???????????? = 222∠0°???? ???????????? = 211∠ − 111°???? ???????????? = 244∠144°????
Calculate:

(a) The symmetrical components of the phase to neutral voltages
(b) The symmetrical components of the line to line voltages
(c) The line to line voltages from their symmetrical components found in (b)
(d) The line to line voltages from original phase voltages
(e) If this source is connected to a Δ connected balanced load with 15Ω resistance in each phase, calculate sequence impedances [10], line currents symmetrical components and the original domain line currents

(f) Use Multisim to check your line current results in (e) [10] (Multisim screenshots need to be provided showing your model and ammeter readings matching your calculation results)

Q3. The single line diagram of a particular power system is shown below. The data of the system is given in the table below. Choose a base power of 100MVA and a base voltage 132kV in Line 3.

(a) Calculate all impedances in pu [8*5]
(b) Draw the impedance diagram of the system and mark all impedances on the diagram
(c) Calculate the line-to-line voltage of Bus 3 in pu and in kV [20] if the motor draws its rated power at rated voltage and pf=0.65 lagging
(d) Calculate the line-to-line voltage of Bus 3 in pu and in kV [20] if the motor is fully compensated at Bus 5 for its reactive power intake