Faculty of Engineering and Built in Environment
Electrical, Electronics and Computer Engineering
Bachelor of Engineering Technology: Electrical Engineering (BPETEE)
POW370S Power Systems 3
Examiner Dr S Krishnamurthy
Moderators: Mr. A. Meru and Mr. T. Jacobs
Graduate Attribute 4 (GA4) Scope
Total marks of 100, weightage of 25% and subminimum of 50%
Contents
1. Description of the Graduate Attribute 4: Investigations, experiments, and data analysis (ECSA
Standard E-02-PT) ................................................................................................................................... 1
2. Technical scope of the Project ............................................................................................................ 2
Part 1: Load flow analysis................................................................................................................... 2
Assumptions: ..................................................................................................................................... 3
Limitations: ....................................................................................................................................... 3
Description of the Newton Raphson Load method ........................................................................ 3
Procedure of Newton Raphson Method .............................................................................................. 4
Part 2: Short-Cricut study ............................................................................................................... 6
Part 3: Overcurrent protection........................................................................................................ 6
Step 4: Project report and submission ............................................................................................ 6
3. Bibliography ........................................................................................................................................ 7
4.
GA4 Rubrics ..................................................................................................................................... 8
1. Description of the Graduate Attribute 4: Investigations, experiments,
and data analysis (ECSA Standard E-02-PT)
Demonstrate competence to design and conduct investigations and experiments.
Range Statement: The balance of investigation and experiment should be appropriate to the
discipline and the definition of a broadly-define problem. Research methodology is to be
applied in research or an investigation where the student engages with selected knowledge in
the research literature of the discipline.
Note: An investigation differs from a design in that the objective is to produce knowledge and
understanding of a phenomenon and a recommended course of action rather than specifying
how an artifact could be produced.
Conduct investigations of broadly defined problems through locating and searching relevant
codes and catalogues, conducting standard tests, experiments, and measurements.
Level descriptor: Investigations, experiments, and data analysis are described by the
range statement:
1
•
•
The balance of investigation and experiment should be appropriate to the sub-discipline.
An investigation differs from a design in that the objective is to produce knowledge and
understanding of a phenomenon and a recommended course of action rather than
specifying how an artifact could be produced.
2. Technical scope of the Project
Part 1: Load flow analysis
The purpose of the project is to model a given 5-bus electrical network in Fig 1 using the data
provided in Tables 1–2 and to perform a load flow analysis using 100MVA and 230kV as the
base. As needed, do the necessary calculations to convert the provided data from p.u to actual
value with the given base. The 5bus power system to be modelled and simulated in DigSilent
Power factory and MATLAB Simscape to validate the load flow simulation results, and the
simulation results will be validated with hands-on calculations for 1st iteration. The analysis
must answer for the voltages, voltage angles, and apparent power at each bus in various
scenarios using a system of equations. The Newton-Raphson iteration approach is used for this
project due to its accuracy and speed in computing load flow.
Bus 5
Figure 1: IEEE 5-BUS SYSTEM DATA (Grainger et al 2003)
Bus Code
P
Table 1 Bus Data for IEEE 5-Bus System
Generation
Load
Assumed Bus
Voltage
Megawatts Megavars Megawatts Megavars
1
1.06 + j0.0
0
0
0
0
2
1.0 + j0.0
40
30
20
10
3
1.0 + j0.0
0
0
45
15
4
1.0 + j0.0
0
0
40
5
5
1.0 + j0.0
0
0
60
10
2
Table 2 Line Data for IEEE 5-Bus System
Line impedance Zpq
Bus Code p – q
R per unit
1-2
0.02
1-3
0.08
2-3
0.06
2-4
0.06
2-5
0.04
3-4
0.01
4-5
0.08
X per unit
0.06
0.24
0.25
0.18
0.12
0.03
0.24
Assumptions:





Three phase loads are connected in delta
All the three phase loads are balanced.
All transmission line lengths are considered as 1km.
AC power flow conducted using Newton Raphson power flow computations.
Convert the P.U quantities to actual using the based of 230kV and 100MVA.
Limitations:
The scope of the project limited Balanced AC Power Flow and Symmetrical fault study.
Description of the Newton Raphson Load method
The Newton Raphson Approach for Load Flow Analysis is a highly effective method for
solving non-linear algebraic problems. When compared to the GS approach, it works faster and
is more likely to converge in most instances. It is, in fact, a realistic approach of solving load
flow problems in huge power networks. Its only disadvantage is the high need for computer
memory, which has been mitigated by a compact storage strategy. Convergence can be
significantly accelerated by executing the first iteration using the GS approach and using the
values obtained to begin the NR iterations.
Newton Raphson Method is an iterative technique for solving a set of various nonlinear
equations with an equal number of unknowns. There are two methods of solutions for the load
flow using Newton Raphson Method. The first method uses rectangular coordinates for the
variables while the second method uses the polar coordinate form. Out of these two methods
the polar coordinate form is used widely.
Before going into detail about how the NR technique is used to address the load flow problem,
it's a good idea to go over the method in its most generic form. The detailed load flow
computation process and its mathematical formulation are described in (Grainger et al 2003)
and (Glover et al. 2015). Let us understand this method with the help of the equations.
3
The above equation (3) and (4) can also be written as shown below.
We have Δf = J ΔX
then I = 1, 2, ….n, I ≠ slack, and if
Where, the subscripts sp and cal denote the specified and calculated values, respectively, then
the equation (7) can be written as shown below.
The off diagonal and diagonal elements of the sub matrices H, N, M and L are determined by
differentiating equation (3) and (4) with respect to δ and |V|.
Procedure of Newton Raphson Method
The computational procedure for Newton Raphson Method using polar coordinate is given
below.
1.
Form Y bus.
4
Assume the initial value of the bus voltages |Vi|0 and phase angle δi0 for i = 2, 3, …..n
for load buses and phase angles for PV buses. Normally we set the assumed bus
voltage magnitude and its phase angle equal to the slack bus quantities |V1| = 1.0, δ1 =
0⁰.
3. Compute Pi and Qi for each load bus from the following equation (5) and (6) shown
above.
4. Now, compute the scheduled errors ΔPi and ΔQi for each load bus from the following
relations given below.
2.
•
•
For PV buses, the exact value of Qi is not specified, but its limits are known. If
the calculated value of Qi is within the limits only ΔPi is calculated. If the
calculated value of Qi is beyond the limits, then an appropriate limit is imposed
and ΔQi is also calculated by subtracting the calculated value of Qi from the
appropriate limit. The bus under consideration is now treated as a load bus.
Compute the elements of the Jacobian matrix.
•
Obtain the value of Δδ and Δ|Vi| from the equation shown below.
•
Using the values of Δδi and Δ|Vi| calculated in the above step, modify the
voltage magnitude and phase angle at all load buses by the equations shown
below.
•
Start the next iteration cycle following the step 2 with the modified values of
|Vi|and δi.
Continue until scheduled errors for all the load buses are within a specified
tolerance that is
•
5
Where, ε denotes the tolerance level for load buses.
•
Calculate the line and power flow at the slack bus.
Part 2: Short-Cricut study
The mathematical representation of symmetrical faults is presented in (Glover et al. 2015).
Perform the symmetrical short circuit study for a 3phase fault at Bus 1 in Power Factory using
IEC 60909 standard with selecting minimum short circuit current option.
Apply the fault impedance of Rf+jXf=(20+j40)ohm
Part 3: Overcurrent protection
The overcurrent protection overview and DigSilent simulation case study are presented in
(Krishnamurthy, 2019). Install the SEL751-1A feeder protection relay and current transformer
at incoming cubicle circuit breaker at Bus 1, then enable the Instantaneous overcurrent
protection element 50P1 with the pickup setting of 120% of full load current and time delay of
20ms. Select the appropriacies CT ratio. Perform the overcurrent engineering setup in
DigSilent Factory and test the 50P1 protection element for a three-phase fault at Bus 1. In
DigSilent, use the Time-overcurrent plot to examine the overcurrent protection.
Step 4: Project report and submission
Prepare a project report of no more than 25 pages that covers the technical aspects of Project
parts 1–3 and is consistent with the GA4 indicators listed in Table 4 below.
The report should cover the following detailed technical scope as per the marking criteria
•
•
•
•
•
Mathematical formulation of the Newton Raphson load flow approach, including the
Jacobian matrix, equality and inequality constraints, and commercial/non-commercial
simulation tools to solve the load flow problem to be investigated. (20)
Review of the state-of-the-art literature on load flow analysis and overcurrent protection
schemes. (30)
Perform hands-on calculations for the first and second iterations of the Newton
Raphson load flow solution methodology/algorithm. (20)
The network modelling and load flow simulation, as well as the analysis of the results,
were carried out using the DigSilent and MATLAB simulation tools.
o Power system modelling in DigSilent PF (5)
o Detailed NR Load flow simulation results analysis (5)
o MATLAB power system modelling in MATLAB Simscape (5)
o MATLAB Load Flow simulation results (5)
Conclusion/ recommendation can be made based on the Short-circuit analysis was used
to design the overcurrent protection setup.
o DigSilent short circuit Study settings and 3ph fault current at Bus 1 (02)
Transformer
and
Overcurrent
protection
configuration
o Current
settings/calculations with OC Characteristics curve in DigSilent (8)
6
Provide all relevant evidences for the parameter configuration settings for the power systems
components in both DigSilent and MATLAB SimScape Tool.
Use a 12-point Times New Roman font with single-line spacing. All figures and tables should
be labelled. Use Harvard referencing throughout the text and provide a reference list. Using the
Institutional safe assign tool to check the similarity index. The report must be free of
grammatical and formatting errors. Copying and any kind of malpractice will be penalized.
Include the GA 4 rubric before the report's cover page.
On or before June 5th, 15:00 hours, submit a printed hardcopy of the GA 4 report to subject
Lecturer Dr S Krishnamurthy, as well as a Black Board submission along with the simulation
models. Late submissions will be penalized 10%.
Table 4: GA4 Investigations, experiments, and data analysis indicators
1. Identifying broadly defined problems for Investigation:
Ability to identify broadly defined problems/issues/topics for investigation. (20%)
Mathematical formulation of the Newton Raphson load flow approach, including the Jacobian matrix, equality and
inequality constraints, and commercial/non-commercial simulation tools to solve the load flow problem to be
investigated.
2. Collection of Background Information:
Ability to gather background information (existing knowledge, research, to identify limitations and implications
and/or indications of the broadly defined problem). (30%)
Review of the state-of-the-art literature on load flow analysis and overcurrent protection schemes.
3. Procedure:
Ability to select OR ability to develop a methodology or theoretical framework to investigate a broadly defined
problem. (20%)
Perform hands-on calculations for the first and second iterations of the Newton Raphson load flow solution
methodology/algorithm.
4. Organizing Evidence: Ability to organize evidence to demonstrate patterns, and highlight differences and/or
similarities. (20%)
The network modelling and load flow simulation, as well as the analysis of the results, were carried out using the
DigSilent and MATLAB simulation tools.
5.
Conclusions and Recommendations:
Ability to state conclusions and make recommendations as a result of the investigation. (10%)
Conclusion/ recommendation can be made based on the Short-circuit analysis was used to design the overcurrent
protection setup.
3. Bibliography
[1] Grainger, J. J., & Stevenson, Jr, W. D. (2003). Power Systems Analysis. New York: Tata McGrawHill.
[2] J. Duncan Glover, Mulukutla S. Sarma, Thomas J. Overbye. (2015).Power system analysis and
design, 6th Edition, Thomson, 978-1-305-63213-4
[3] S. Krishnamurthy. (2019). Protective Relaying System Book Chapter. Power System Protection in
Smart Grid Environment, pages 162-193, 1st Edition, CRC Press Taylor and Francis, eBook
ISBN9780429401756
END
7
4. GA4 Rubrics
GA4: Investigation: Examination and Evaluation
Subject & code:
Examiner name:
Student name and number:
1 (0-25%)
2 (26-49%)
3 (50-75%)
4 (76-100%)
INDICATORS & WEIGHTING
Needs work
Developing
Competent
Strong
1. Identifying broadly defined problems
for Investigation:
Ability to identify broadly defined
problems/issues/topics for
investigation. (20%)
Minimal or no ability to identify
broadly defined
problems/issues/topics that may
or may not require investigation.
Some ability to identify broadly
defined
problems/issues/topics that
may or may not require
investigation.
Identifies relevant broadly
defined
problems/issues/topics with
minimal orientation, that
require investigation.
2. Collection of Background Information:
Ability to gather background
information (existing knowledge,
research, to identify limitations and
implications and/or indications of the
broadly defined problem). (30%)
Minimal or no ability to collect
relevant background information.
Collects some relevant
background information from
appropriate sources.
3. Procedure:
Ability to select OR ability to develop a
methodology or theoretical framework
to investigate a broadly defined problem.
(20%)
Minimal or no ability to
select/develop a methodology or
theoretical framework.
Minimal or no ability to organize
evidence.
4. Organizing Evidence: Ability to
organize evidence to demonstrate
patterns, and highlight differences
and/or similarities. (20%)
Assessor'
Rating
Student
Score (%)
Identifies relevant broadly defined
problems/issues/topics with
minimal or no orientation, and is
able to select those that are
pertinent/critical for investigation.
4
20
Collects sufficient relevant
background information from
appropriate sources.
Collects sufficient relevant
background information from
appropriate sources, and is able to
identify pertinent/critical
information.
4
30
Selects/develops a
methodology or theoretical
framework that is somewhat
appropriate.
Selects/develops an
appropriate methodology or
theoretical framework.
Selects/develops an optimal
methodology or theoretical
framework.
4
20
Organizes evidence in a way
that is somewhat effective in
demonstrating patterns,
differences, and/or similarities
that are applicable to the
investigation.
Organizes evidence to
demonstrate patterns,
differences and/or similarities
important to the investigation.
Organizes evidence with
perception, demonstrating
patterns, and highlighting
differences and/or similarities
integral to the investigation.
4
20
8
5. Conclusions and Recommendations:
Ability to state conclusions and make
recommendations as a result of the
investigation. (10%)
Minimal or no ability to state
conclusions or make
recommendations.
States conclusions and makes
recommendations that may or
may not be relevant to the
investigation.
States logical conclusions and
makes appropriate
recommendations.
States logical conclusions and
makes insightful
recommendations, and identifies
those that are pertinent/critical.
Final Mark (%)
Examiner:
Internal moderator:
External moderator:
9
10
4
100