ECE 427 Assessment 2 – Part II: Take Home Exam – Transmission Line Design
You’re an engineer on a team that is designing a brand-new overhead transmission line from Dubuque, Iowa, to Madison. This would allow more wind power to flow from Iowa to the population centers in southern Wisconsin.
The three-phase 60 Hz, 345 kV line will have a length of 160 km.
Below, you are given a selection of conductors with different names (power line designers like birds) and different sizes, diameters, resistance, and cost. These values are given for a single conductor.
In your calculations, you can assume that the conductors are solid cylinders with the given diameters. Also, assume that the conductor temperature stays at 25°C.
You can also choose between several bundle configurations and tower configurations, given below.
The design optimization goal is to minimize the following cost function by choosing the conductors, their configuration, and determining the resulting line parameters and the cost. The cost function is defined as:
Where
• CF = Cost function to minimize in the design process
• line$ = total cost of conductor material in USD (You can neglect sagging here, assuming a length of 160 km for each conductor you use.)
• plo(r)ss(at)ed = Line losses calculated using Ir(2)atedR where R is the per-phase resistance in km/Ω and the
per-phase rated current is Irated = 0.7KA.
• is the characteristic impedance of the line when it is assumed to be lossless, and
L and C are the per-phase inductance and capacitance in m/H and m/F, respectively.
Remember: Make sure that your design is presented in a clean, readable way when you submit it!
While you may have gone through several design iterations and a lot of scribbling and thinking while creating your designs, you want the designs that you submit in the end to be well presented.
This will allow your boss, your co-workers (and your instructors in this class!) to easily understand what design you chose and why, and to follow how you computed the parameters and the cost.
Conductors:
|
Name
|
Size (kcmil)
|
Diameter (cm)
|
Resistance (Ω/km @ 25° C, 60 Hz)
|
Cost (USD/m)
|
|
Chickadee
|
397.5
|
1.887
|
0.14469
|
$3.18
|
|
Pelican
|
477
|
2.068
|
0.12073
|
$3.94
|
|
Osprey
|
556.5
|
2.233
|
0.10400
|
$4.79
|
|
Drake
|
795
|
2.814
|
0.07185
|
$7.81
|
|
Cardinal
|
954
|
3.038
|
0.06135
|
$8.83
|
|
Ortolan
|
1033.5
|
3.078
|
0.05774
|
$9.32
|
|
Bittern
|
1272
|
3.416
|
0.04757
|
$10.76
|
|
Lapwing
|
1590
|
3.820
|
0.03871
|
$14.01
|
Bundle configurations:
Tower configurations: (dimensions are in [feet]’[inches]”)
The design process you should follow:
1. First calculate the cost function for a baseline design using the following parameters:
• Conductor: Drake
• Bundle configuration 2
• Tower configuration 3L1
2. Create at least two additional designs to investigate the impact of different design choices on the cost function and try to get to a close-to-optimal design (with the lowest cost possible). For each iteration, describe all your design choices and calculations in detail. Then, summarize the changes you made and your observations about the design in each iteration in the Table below.
3. Once you are done with your exploration, explain which of your designs you would recommend building and why.
Note: You are NOT expected to test all possible configurations and find the optimal design. Just use your intuition to improve upon the baseline design as much as you can.
Grading:
The grade will be based on
(20%) correct calculations (with sufficient explanation) for the baseline design,
(55%) clear explanations and correct calculations in each of the iterations,
(20%) clear summary and well-justified conclusions regarding the best design,
(5%) clarity of presentation.