This project aims to determine your ability to apply the concepts and methods discussed in class
for a power system design problem. You can develop your own software in your language of
choice, and/or use the software tools utilized in the class (i.e. MATLAB).
● To carry out the design of a power transmission system that runs through both urban and
rural service territories.
● To apply your knowledge from class in computing parameters for component models,
perform steady-state analysis.
● To build software scripts and use different software tools towards your design.
● To document your results and source code in a report.
Design Project Statement and Data
Design Problem Statement
The design problem consists in expanding a transmission system to serve a new data center
called “Steel Mill” (indicated with a red square in the map in Fig. 1) and to also determine if the
existing transmission system needs to be upgraded to handle a 30% growth in the existing load.
This requires to design and build new transmission infrastructure, and to perform power flow
The transmission system in Figure 1, below, contains both 161 kV and 69 kV transmission lines
and substations that go through both urban and rural service territories. Assume that all roads go
from North to South and East to West. The load at each of the buses is provided in Table 1, and
the parameters of the existing lines are shown in Table 2.
Figure 1. Eagle Power System One-line Diagram
Substations Buses and Loads
The buses shown in the diagram correspond not only to electrical buses, but to substations that
may contain transformers and other components as discussed next:
● Buses 1-3 are substations at power sources (i.e. generation plants) at 161 kV.
○ Each power source is rated at 490 MW, with a minimum volt ampere
reactive limit of -100 MVAr and a maximum limit of 250 MVAr.
● Buses 4-8 are urban load substations
● Buses 4-9 are rural load substations
Buses with loads under 30 MVA should be served at 69 kV and buses with loads over 50 MVA
should be served at 161 kV. Other buses can be served at either voltage, as discussed later.
Bus # Bus Name Load (MW) Load (MVAr)
4 Lark 60 10
5 Jay 100 30
6 Raven 80 15
7 Wren 90 20
8 Robin 40 5
9 Siskin 10 5
10 Junco 15 10
11 Quail 75 15
12 Heron 40 15
13 Egret 30 10
14 Gull 35 10
15 Crow 10 0
Total: 585 145
Table 1. Loads at different buses
There are 69 kV to 161 kV transformers with 60 MVA rating at the Siskin and Crow buses. Each
of the buses have 2 voltage levels. At Siskin, the high voltage side is labeled bus 9, while the low
voltage side is labeled bus 17. At Crow, the high voltage side is labeled bus 15, while the low
voltage side is labeled bus 16. The transformers have leakage reactance of 34.56Ω referred to
the 161 kV side.
To simplify the study, Tap changer setting for all transformers is 1.
Parameters for Existing Lines
The parameters of the existing transmission lines are provided in Table 2, below.
Bus # Bus # Bus Name Bus Name Miles Conductor R (Ohmns) X (Ohmns) BMVA
1 9 Owl 161 Siskin 161 24 Drake 3.085 17.47 3.629
1 11 Owl 161 Quail 161 36.7 Drake 4.718 26.7 5.55
1 14 Owl 161 Gull 161 28.2 Drake 3.629 20.53 4.264
2 11 Swift 161 Quail 161 21.5 Drake 2.774 15.66 3.251
2 12 Swift 161 Heron 161 20.3 Drake 2.618 14.78 3.07
2 14 Swift 161 Gull 161 24 Drake 3.085 17.47 3.629
3 6 Parrot 161 Raven 161 27.6 Drake 3.551 20.09 4.174
3 12 Parrot 161 Heron 161 27.6 Drake 3.551 20.09 4.174
3 15 Parrot 161 Crow 161 23.6 Drake 3.033 17.16 3.569
4 5 Lark 161 Jay 161 8.4 Dove 1.529 6.3 1.232
4 9 Lark 161 Siskin 161 18.8 Drake 2.411 13.69 2.843
5 6 Jay 161 Raven 161 10.8 Dove 1.97 8.09 1.584
5 7 Jay 161 Wren 161 6 Dove 1.089 4.48 0.88
5 8 Jay 161 Robin 161 10.9 Dove 1.996 8.17 1.599
7 15 Wren 161 Crow 161 14.6 Drake 1.866 10.63 2.208
8 12 Robin 161 Heron 161 9.8 Drake 1.27 7.13 1.482
5 11 Jay 161 Quail 161 19.5 Drake 2.514 14.18 2.949
10 13 Junco 69 Egret 69 14.3 Hawk 3.033 10.15 0.408
10 17 Junco 69 Siskin 69 16.2 Hawk 3.433 11.49 0.462
13 16 Egret 69 Crow 69 21.9 Hawk 4.642 15.54 0.624
BMVA: reactive volt-amperes generated by the total susceptance corresponding to line charging of the
transmission line at rated voltage.
Table 2. Transmission Line Parameters
The BMVA is determined as follows. The susceptance of the line as , consequently
the BMVA can be calculated from:
● Conductor Types: For new lines that have to be built the only conductors available to
use are Partridge, Hawk, Dove, Drake and Cardinal, and their data is available in the
● Ampacity: the maximum current carrying capacity (or ampacity) of the allowable
conductors types listed above are: Partridge (475 A), Hawk (659 A), Dove (726 A),
Drake (907 A), Cardinal (996 A).
The project is structured so that you conduct this project in 6 different phases, as follows:
1. In the first phase of the design, the only requirement is to choose the conductors for the
two voltage levels, and determine the corresponding impedance parameters of the lines
(series resistance and reactance, and one-half the total capacitance of susceptance,
2. The following phase consists of transforming all the data to per unit quantities.
3. The third phase of the design requires to consider the location of the power generators
and to determine from data tables what the most adequate parameters to use are.
Tips: (MW, Mvar, Qmin, Qmax)
4. The fourth phase consists in using the per-unit data of all system components to compute
both Ybus and Zbus.
5. The fifth phase consists in a power flow study of the system under different load growth
6. The final phase is to prepare a report describing obtained results based on this analysis.
In this phase you are asked to upgrade the existing system making better design to serve the
load and generation subject to the following specifications and design tasks.
a. Provide sufficient capacity in the transmission lines and transformers for a 30% growth of
the existing load.
b. The new “Steel Mill Data Center” will host a major IT operation for the new crucial
Infrastructure. This will be a critical load. It is estimated that the load will be 40 MW at unity
power factor, and will be located as shown in the map in Fig. 1. Design a suitable
transmission system to supply the load.
c. Transmission voltages of 161 kV or 69 kV can be used. Bundled conductors are not to be
used at these voltages.
d. Calculate impedances of all the new transmission lines using a suitable software. You can
make your own, or use MATLAB. The resistance of lines should be calculated at 50 deg.
C. The line capacitance in terms of the megavolt-amperes-reactive (MVAr) generated by
the total capacitance of susceptance at rated voltage is provided in Table 2. You need to
calculate these quantities for any new transmission line added.
e. Each power source (generator) should be connected to the rest of the system by at least
three 161 kV lines.
f. Do not oversize conductors without justification.
g. The maximum number of available transformers is four.
h. It is unlikely that you can justify using the same conductor size at both 161 kV and 69 kV.
Design Criteria and Specifications
In performing the above steps, you will need to verify that the transmission lines and transformers
have sufficient current carrying capacity (ampacity) at steady-state in this project. This can be
done accurately using power flow calculation programs, as done in the fifth phase. In this phase,
however, you should instead start by making an estimate.
To compute this estimate, you can take an intuitive approach. Because you are given the existing
voltages and loads at each bus, you can compute an estimate of the load currents. For simplicity,
assume that increasing the loads by 30% increases the currents proportionally. Once the current
of a particular bus has been determined, the next step is to figure out how much of this current is
supplied by each of the transmission lines to the bus. Of course, one could use the current divider
approach, however, this would require additional data and computations that are not possible at
In this phase, you can use the concept of “electrical distance”. The electrical distance is a
measure of the equivalent impedance between two nodes. When 2 buses are electrically close,
the equivalent impedance between them is low, and vice versa. While geographical closeness
and electrical closeness are mostly related, this is not always the case, as it depends on the value
of the impedances between two buses. For example, intuitively, bus 11 is connected to generator
bus 1 through a single line, whereas there are many other lines and equipment from bus 3 to
generator bus 11. So, you can expect that at bus 11 there is more current coming from bus 1 than
Hence, a simplified approach to quantify electrical closeness is to consider a particular
load bus and determine the impedance of all paths between the load bus and generator buses.
First, you can calculate the impedance for all possible transmission paths between bus 11 and
generator bus 1, which include pats (1-11), (1-14-2-11), (1-9-4-5-11), etc. Next, find the lowest
impedance path. In practice, some paths (those with many segments) can be ignored. If the result
is a low impedance, bus 11 is “close” to generator bus 1. Similarly, it is possible to find the lowest
impedance path from bus 11 to bus 2, and from bus 11 to bus 3. For simplicity, it can be assumed
that the currents to bus 11 only flow in the three lowest impedance paths and that they divide
according to the parallel current rule. Thus, the lower the path impedance, the greater the fraction
of the total current that flows in that path. This should provide results that would be reasonable,
at least qualitative.
This phase consists in transforming the data from the system designed in Phase 1 to per unit.
For the system designed in Phase 1:
i. Calculate all the impedances on a 100 MVA base, with a voltage base of 161 kV or 69 kV
j. The transformer reactance is 0.08 pu on the transformer base. You can ignore the
resistance or find the value in per unit by making your own assumptions.
Create a table with all the parameters of the system in per unit.
This phase consists in determining a location of the generators and parameters (MW, Mvar, Qmin,
Qmax) from data tables what the most adequate parameters to use in the system.
The power system in Fig. 1 has three power generation plants located at Bus 1 (Owl), Bus 2
(Swift) and Bus 3 (Parrot). Assume that these three generators have a rating of 550 MVA each,
and recall that each of the generators is rated at 490 + j250 MVA.
k. Convert all machine parameters to a common system base of 100 MVA and the
This phase is a continuation of Phases 3 and 4 and consists of building the Ybus and Zbus
For the parameters determined in Phases 3 and 4, perform the following calculations.
l. use the MATLAB Command other code to compute Ybus and Zbus.
m. Compute the Ybus and Zbus matrices with all the parameters expressed in per unit on the
common system base of 100 MVA.
This phase consists in performing different power flow studies for the system set up in the previous
phases. You will consider the following case studies:
● Case 1: Base case system with base loads and fixed tap transformers (tap setting 1)
● Case 2: Modified system with 40 MW “Steel Mill Data Center” load and base case loads
increased by 30% and fixed tap transformers.
n. Use the software of your choice to perform power flow analysis on Case 1 and verify the
design requirements listed below.
o. Modify the transmission system to supply the new 40 MW load following the specifications
a-j in Phase 1.
○ Obtain the parameters of the lines as needed by the power flow program of your
choice, and provide a new table of data highlighting the new parameters used.
○ Use the software of your choice to perform power flow analysis on Case 2 and
verify the design requirements listed below.
p. Summarize graphically (one plot for the same variable for the two Cases) the power flow
results from the two cases analyzed above, show the bus voltage magnitude and angle,
active and reactive powers.
q. Determine the total power (P) loss in the system as a percentage of the total load for each
case. Compare the MVA in the loads, the MVA used in the lines and the transformers, and
the MVA from the generators in each case.
Design Criteria and Specifications
When carrying out the design tasks above, you must meet the following design criteria:
● R1. Satisfactory system operation: all voltages should be in the range from 0.96 to 1.04
pu, with no overloaded lines or transformers.
● R2. Loads: from the power flow results, determine the total load in the system, the losses
and total generation.
● R3. Transformers: the transformer tap should be fixed at 1.00 (Tap 1 for both the 69 kV
and 161 kV) in the power flow for Case 1 and Case 2.
For Case 2, If any of the criteria above are violated you will need to modify your design at your
best effort and re-do the analysis until the modified system meets the criteria.
The specifications below are to assist you in meeting the design criteria.
● S1. Generation:
○ Make Bus 1 (Owl) the slack/swing bus.
○ For the generation at Bus 2 (Swift) and at Bus 3 (Parrot) change the following at
both: Qmin – 100.00 MVA and Qmax 250.00 MVA, and Pmax at 430 MW.
○ In Cases 1, Pgen at each bus (2 and 3) should be 190 MW. In Case 2, change the
Pgen at each bus to more appropriate values. Since the voltage is usually highest
at generator buses, and since 1.04 is at the upper limit of acceptable voltages,
schedule the voltage on the three generators at or near 1.04 per unit.
● S2. Naming Conventions and Plotting: for each power flow you run, you must
summarize the results in graphical form (e.g. using bar plots) and in the title, you need to
specify the case as for Case 1, or for Case 2.
● S3. Check your data!: as you will have to modify either the one-line diagram or data files
for the power flow program, you need to be careful when modifying it. Be consistent with
naming conventions you will use as you make modifications to each case, use descriptive
names, and add comments to the source file or diagram. Spend time checking that you
are applying the correct changes to the files and that they are modifying the output as
expected. Also check that all the lines are connected to the correct buses. Typical issues
when doing these studies
This final phase is about documentation of your obtained results considering the below guidelines:
A deadline for report submission is on December 11th, 2020 by 5:00 pm.
Report Requirements and Structure
Your report should be structured as described below.
1. Executive Summary: a maximum 1-3 page summary that includes the main information
of your project.
This should contain everything that I need to know to grade you without having to read
the whole report. Make this a “self contained” document.
Your summary should include at least the following:
a. Total number of lines at each voltage level, total line at each voltage level.
b. The total number of transformers
c. Summarize the changes required at each phase using a table. Make a table that
has as either rows or columns the relevant phases (i.e. Phase 1, 3, and 4).
d. Contrast the analysis methods and results of Phase 1, 4, and 5.
e. Use a minimum of 1 figure and a maximum of 2 figures to highlight your most
2. Report Structure:
a. Title page
b. Table of contents.
c. System Description
i. A one-line diagram of the system showing the bus, line, transformer, and
load connections. Don’t forget to include capacitor banks if they are needed
in based on your results in Phase 5. They should be as part of your
suggestion to achieve a better system operation.
ii. Specifications of each line in the system: connection between buses,
voltage, length, conductor size, series impedance and shunt capacitance
susceptance, and MVA and current ratings. For the new lines added to
supply the “Steel Mill Data Center”, show a sample impedance and
susceptance calculation. Summarize all remaining results from Phase 1 in
a dedicated Appendix.
d. Design Summary
i. Provide a summary of results from all other design phases here. You
should aim to summarize each phase with a short paragraph and preferably
through 1 or 2 figures. You might prefer that all other details (calculations,
tables, figures) for each design phase to be included in a dedicated
ii. Design Analysis:
1. Summarize the changes required at each phase using a table.
Make a table that has as either rows or columns the relevant phases
(i.e. Phase 1, 4, and 5).
2. Compare the analysis methods and results of Phase 1, 4, and 5.
3. Use a minimum of 1 figure and a maximum of 2 figures to highlight
your most important finding.
iii. Design Tools:
1. Software Documentation: Briefly explain, through a flowchart and
discussion, how you were able to do the analysis required through
different software routines or by using different functions/software
and reading data.
e. Conclusions: briefly discuss your findings. Keep this short, 1-2 paragraphs, 1
figure, and highlight your most important finding.
a. Number and title all figures.
b. Number and title all tables.
c. Document all changes made from the base case design in a dedicated Appendix,
Do your own work!
● This project serves as a way to measure your ability to apply the intended learning
outcomes. You must make sure during the course that you will be able to do the work
described here, and thus, you must do all the homework assignments to be able to have
the skills you need.
● This project may have not a unique solution, so there is likely possible way that you
can have the different solution as another student.
Appendix – Conductor Data for Transmission Lines
Figure 2. Bare Aluminum Conductors, Steel Reinforced (ACSR) Electrical Properties of Multilayer Sizes
Figure 3. Bare Aluminum Conductors, Steel Reinforced (ACSR) Electrical Properties of Multilayer Sizes
Figure 4. Bare Aluminum Conductors, Steel Reinforced (ACSR) Electrical Properties of Multilayer Sizes