RExamination Paper
Examination Session:
May/June
Year:
2022
Exam Code:
ENGI4487-WE01/
ENGI44I10-WE01
Title: (MEng/MSc)
Smart Energy Networks 4
Time Allowed: 2 hours
Additional Material provided: No
Reporting problems during
the exam:
Queries about the instructions for this exam (rubric) should be directed to:
eng.boe@durham.ac.uk.
If you experience any difficulties uploading your exam answers to
Gradescope report these immediately to: eng.boe@durham.ac.uk.
Instructions to Candidates: Answer ALL questions.
Please answer each question on a new page.
All workings must be shown.
This is an online open-book exam, submission is time-limited to 4 hours
within a 24 hrs window.
 The examination attempt must be all your own work. You must not
interact with another person (either one-to-one, by telephone, on the
internet, in chat rooms, on social media, via smart watches, etc.), or use
cheat sites, etc. whilst completing the exam. You must not discuss any
examination papers with friends, relatives, current or past students of this
or any other University before the end of the relevant 24-hour window.
 Candidates are expected to answer all questions in their own words.
Should close paraphrasing, direct quotation be necessary candidates
must acknowledge the source of any material used in their answers (this
includes text, images, diagrams, charts, tables and/or graphs). Full
referencing is not expected, but a brief indication of the source of the
material (e.g. name of author) must be given.
Revision:
Page 2 of 4 ENGI4487-WE01/
ENGI44I10-WE01
continued
Section A
Question 1
(a) Thévenin equivalent sequence networks looking into the faulted bus of a power system are
given with ଵ = 0.33, ଶ = 0.41, ଴ = 0.35 , and = 1∠0° per unit. Compute the phase
currents (௔௕௖), the fault current, and also the phase voltages (௔௕௖) for the following faults at the
faulted bus:
(i) Line-to-line fault.
(ii) Balanced three-phase fault.
[20%]
(b) Consider a three-bus power network for which the ௕௨௦ matrix is shown below. In this network,
two generators are connected using series impedances at buses 1 and 2 respectively. Find the
bus voltages after a three-phase bolted fault on bus 3 of this system. Also find the sub-transient
current in line 1-3. Neglect prefault currents.
௕௨௦ = ൥
−6.5 2 2
2 −8.5 4
2 4 −10
൩
[20%]
Page 3 of 4 ENGI4487-WE01/
ENGI44I10-WE01
continued
(c) A 50-Hz synchronous generator has a transient reactance of 0.2 per unit and an inertia constant
of 4 MJ/MVA. The generator is connected to an infinite bus through a transformer and a double
circuit transmission line, as shown in Figure Q1. Resistances are neglected and reactances are
expressed on a common MVA base and are marked on the diagram. The generator is delivering
a real power of 0.93 per unit to bus 1. Voltage magnitude at bus 1 is 1.05. The infinite bus
voltage is ௕௨௦ = 1.0∠0° per unit.
(i) Determine the swing equation.
(ii) Assume that a permanent three-phase bolted fault occurs on one of the parallel
transmission lines at distance x from bus 1. The fault is cleared by operating the circuit
breakers at the ends of that line and those circuit breakers then remain open. Determine
the electric power ௘ during the fault for three different cases where x=0, x=0.3L and x=L,
where L is the length of the parallel lines. Draw the equal area curves for these cases,
and explain how changes in x affect the stability of the system.
Figure Q1
[60%]
Page 4 of 4 ENGI4487-WE01/
ENGI44I10-WE01
continued
Section B
Question 2
Write an essay to discuss important roles of demand side management (DSM) technologies in
future power systems for achieving the Net-zero goal. Use Durham University’s Engineering
Department as an example to explain and discuss how DSM technologies can be used to improve
economic and energy efficiency of the electric system. Graphs can be used for assisting your
explanations and discussions.
Within the essay, you may need to consider the following points:
 What future power systems will look like to achieve the Net-zero goal?
[20%]
 What are DSM technologies? And their effects and benefits in power systems?
[20%]
 How can DSM technologies benefit the Engineering Department?
[20%]
 What devices, consumers engagement, and/or education programmes will be needed in
the Engineering Department?
[20%]
 Show your vision about what the Department will look like to achieve the Net-zero goal,
and summarise main viewpoints.
[20%]
Note: Make sure to provide evidence and/or discussions to support your viewpoints.
END