Hello,
I'm glad there is new test system based on real data. While browsing
through http://lup.lub.lu.se/student-papers/record/9124806, I noticed
something worth discussing. Figure 3.3 (p. 20) illustrates merging
parallel branches into a single equivalent branch by simply adding the
individual branch rated currents. However, this method isn't entirely
accurate. For instance, if we consider two 20 kV cables from
https://nkt.widen.net/content/iveqn7cqgj/pdf/230529_AXAL-TT-Pro-3_24kV.pdf?u=gj0n1y,
with cross-sections of 25 mm^2 and 50 mm^2 and rated currents of 100 A
and 145 A respectively, the equivalent cable rated current wouldn't be
245 A.
Generally, all cables exhibit similar reactance per unit length
regardless of their cross-sections. However, the resistance ratio is
approximately 2 due to the second cable's doubled cross-section compared
to the first one. Consequently, applying the current divider principle
becomes necessary to determine the proportion of total current flowing
through each parallel cable.
In the attached file, I've computed three scenarios:
1. Equal length for both cables,
2. The first cable is 20% longer,
3. The second cable is 20% longer.
The equivalent rated current for the parallel combination is calculated
so that one cable carries current equal to its rated current. The
results for the three scenarios are:
1. 223 A,
2. 210 A,
3. 238 A.
I believe it would be beneficial to perform similar calculations for the
actual cables in the test system to validate if corrections to the rated
current are necessary.
Best regards,
Mirko
On 12/6/23 18:28, Ray Daniel Zimmerman wrote:
Hello Gabriel,
I’d be happy to include this in the next MATPOWER release. I’ve
attached a version with a few tweaks to the comments at the beginning
of the file (no data changes). Please check that they are ok with you
and the providers of the original data.
I added some of the description of the system that you included in
your e-mail. And I added copyright and license lines. Whenever
possible we like to include an explicit license for all MATPOWER
files, BSD 3-clause license for code and the Creative Commons
Attribution 4.0 International license for data.
If these are ok with you, please go ahead and create a pull request on
GitHub to add the file.
Thanks again for this contribution!
Ray
On Nov 30, 2023, at 10:38 AM, Ray Daniel Zimmerman <r...@cornell.edu>
wrote:
Absolutely, we would be interested in including this. Let me have a
look at it and get back to you about any suggested modifications.
Ray
On Nov 29, 2023, at 9:13 AM, Gabriel Malmer
<gabriel.mal...@iea.lth.se> wrote:
Dear Matpower-developers,
My name is Gabriel Malmer and I’m a PhD student in power systems at
Lund University.
For my master’s thesis, me and my colleague Lovisa Thorin developed
a 533-bus distribution system in Matpower, based on real system data
from the local DSO Kraftringen in southern Sweden.
Kraftringen have agreed to have this Matpower-case publically
available, and I was wondering if this would be of interest for the
Matpower data-package? See attached file, case533mt.m.
If this is of interest, please let me know and I can add it to the
Matpower GitHub. Also feel free to suggest modifications to make the
case-file more adequate.
Some general information: The system covers about 20x30 km and
servers about 30,000 inhabitants + an industrial area. Total net
loads between -5 and 50 MW. Right now, the loads included are the
net loads from the/minimum/load hour of 2022.
For more information,
seehttp://lup.lub.lu.se/student-papers/record/9124806
<http://lup.lub.lu.se/student-papers/record/9124806>.
<image001.png>
Kind regards,
*Gabriel Malmer*
Doktorand
LTH, Lunds universitet
Avd. för Industriell Elektroteknik och Automation (IEA)
Postadress: Box 118, 221 00 Lund
Besöksadress: Ole Römers väg 1, 223 63 Lund
<case533mt.m>
% see figure 3.3 from: http://lup.lub.lu.se/student-papers/record/9124806
% cable data from: https://nkt.widen.net/content/iveqn7cqgj/pdf/230529_AXAL-TT-Pro-3_24kV.pdf?u=gj0n1y
% frequency
f = 50; % Hz
% cable 1: 25 mm^2
R1 = 1.2; % Ohm/km
L1 = 0.13; % inductance mH/km
X1 = 2*pi*f*L1/1000; % Ohms/km
I1_rated = 100; % Nominal load current (in soil)
% cable 2: 50 mm^2
R2 = 0.641; % Ohm/km
L2 = 0.15; % inductance mH/km
X2 = 2*pi*f*L2/1000; % Ohm/km
I2_rated = 145; % Nominal load current (in soil)
disp('sum of cables nominal load currents');
I_sum = I1_rated + I2_rated
disp('parallel cables with equal length');
Z1 = R1 + 1j*X1;
Z2 = R2 + 1j*X2;
% current divider
k1 = abs(Z2/(Z1 + Z2));
k2 = abs(Z1/(Z1 + Z2));
I_rated = min([I1_rated/k1 I2_rated/k2])
disp('parallel cables, cable 1 is 20% longer');
Z1 = 1.2*(R1 + 1j*X1);
Z2 = R2 + 1j*X2;
% current divider
k1 = abs(Z2/(Z1 + Z2));
k2 = abs(Z1/(Z1 + Z2));
I_rated = min([I1_rated/k1 I2_rated/k2])
disp('parallel cables, cable 2 is 20% longer');
Z1 = R1 + 1j*X1;
Z2 = 1.2*(R2 + 1j*X2);
% current divider
k1 = abs(Z2/(Z1 + Z2));
k2 = abs(Z1/(Z1 + Z2));
I_rated = min([I1_rated/k1 I2_rated/k2])
