IEEE 123 node distribution feeder model with Compensated Stublines and SSN
IEEE 123 node distribution feeder diagram. Compensated stubline locations and lengths in feet are shown.
This model is used to demonstrate the Compensated Stubline model and its usage on the IEEE 123 Node Test Feeder.
In the model, four Compensated Stublines are used to decouple the complete circuit into 3 independent sets of equations, each one of these solved with SSN.
The 4 pi-lines lines, replaced by Compensated Stublines, have lengths between 700 and 1000 ft (0.3 km). The stublines that replace them have a 1-time step (Ts) propagation delay and with the same total inductance (L), so it could be considered as having an equivalent length of ~14km at 50 us.
This increase line length typically brings some errors due to the increased capacitance (C) of the stubline line (C=Ts^2/L). The Compensated Stubline technique has the objective of minimizing the error of the stubline model.
Demonstration test case
In this test we compare 2 different simulations:
1- Native SPS solver with nominal pi-line
2- SSN solver (art5) with Compensated Stubline
All SSN cases have an SSN-OLTC transformer while a regular power transformer is used for the SPS case.(SPS does not have an OLTC model compatible with real-time). The simulation time step is 50 us.
A phase-to-phase fault is made at Bus 23 for comparison purposes. The figure below compares the 2 simulation results for Bus23 voltages and currents and the main feeder currents; it shows that all curves match very well during the test.
Input feeder currents and Bus 23 voltages and currents during the phase-to-phase fault
This model was originally provided by Yan Chen, Daniele Carta, and Andrea Benigni (Department of Electrical Engineering, University of South Carolina). Model modified by Christian Dufour (Opal-RT) and Abdelrahman Karrar (University of Tennessee at Chattanooga) for Compensated Stublines, SSN OLTC transformers, and custom pi-lines.
 B. Ahmed, A. Abdelgadir, N. Saied, and A. Karrar, "A Compensated Distributed-Parameter Line Decoupling Approach for Real-Time Applications" in IEEE Transactions on Smart Grid, DOI: 10.1109/TSG.2020.3033145.