How WSU used ETAP to model and verify IEEE benchmark testing of feeder systems with distributed energy resources

DER integration with smart inverters following industry standards, such as California Rule 21, enables realistic simulations of grid support behavior.
By Vivek A Jayaraman, Power Engineer, ETAP

Washington State University collaborated with ETAP to model and analyze the IEEE 123-node benchmark test feeder system as part of a U.S. Department of Energy project. This work demonstrates the methodology for building and validating the system model in ETAP, then conducting ADMS-related studies with and without photovoltaic distributed energy resources (DER) equipped with smart inverters. The study explored including volt-VAR optimization, switching optimization, fault management, service restoration, and three-phase unbalanced load flow. As a result of this study, the IEEE 123-node system is now included as an example project in ETAP.

Washington State University is a public land-grant research university in Pullman, Washington, United States. Founded in 1890, WSU is also one of the oldest land-grant universities in the American West. The Office of Research (OR) is a constellation of six primary offices and many supporting labs, centers, and institutes. Each office offers specialized expertise in various aspects of research support. WSU’s Energy Systems Innovation Center is at the forefront of global research, education, technology innovation, and transfer for energy systems, including smart grids.

Location: Pullman, Washington, USA

Year: 2023

Radial distribution network modeling and analysis

Challenges

1. Accurate representation of the IEEE 123-node test feeder

The system is a 4.16 kV radial distribution feeder consisting of:
  • Multiple three-phase and single-phase branches
  • 85 lumped loads (constant current, constant impedance, constant kVA)
  • 4 voltage regulators
  • 4 capacitor banks
  • 11 SPST switches
  • 2 transformers

This makes it ideal for evaluating VVO, FLISR, switching optimization, and DER hosting.

2. Load modeling constraints

In this release, single-phase constant-current loads could not be directly modeled in ETAP (This functionality was added to ETAP after this case study was performed.)
They were converted to 50% constant impedance / 50% constant kVA equivalent loads.
A later Revision 1 changed all loads to 100% constant impedance, which is the correct assumption for CVR/VVO (Volt-VAR optimization / conservation voltage reduction ) studies where voltage reduction should reduce demand.

3. Complexity in line and branch modeling

The feeder includes:
  • 116 overhead lines with 12 unique configurations
  • 5 underground cable sections modeled via impedance matrices
  • Additional switching nodes enabling DER blocks to be connected or isolated

4. Matching IEEE benchmark results

Load-flow outputs were validated against IEEE reference data
  • Minor deviations were attributed to load modeling constraints
  • At the time, the lack of asymmetric regulator impedance modeling in ETAP (Added as a feature after this case study.)

5. Performing ADMS-related studies

The validated model was then used for:
  • Switching Optimization
  • Fault Management & Service Restoration (FLISR)
  • Volt-VAR Optimization (VVO/CVR)
  • Analysis with and without DER penetration

Which solutions did they choose for research?

Selected applications

ETAP Power Simulator, for DER modeling with smart inverter Volt-VAR curves, three-phase unbalanced load flow and VVO/CVR.
ETAP Grid™ advanced distribution management software for switching optimization (loss minimization) and FLISR.

Why do they use ETAP?

Main customer benefits

1. IEEE 123-node feeder provided out of the box

The test system is now included as a built-in project in ETAP, enabling researchers to immediately explore ADMS and DER studies without building the model from scratch.

2. Multidimensional database with revisions

With the functionality of revision management provided by ETAP, load assumptions could be modified (such as converting all loads to 100% impedance) without altering the topology of the network.

3. Comprehensive system modeling environment

ETAP provides detailed models for:
  • Overhead and underground lines
  • Transformers
  • Voltage regulators
  • Capacitors
  • PV systems with smart inverters (following Rule 21 curves)
  • DER switching schemes

4. Unified platform for advanced ADMS studies

Switching optimization, VVO/CVR, FLISR, and DER integration studies can all be conducted within the same model and analytical environment.

5. Clear visualization and validation tools

ETAP’s graphical outputs - voltage profiles, regulator actions, DER reactive power, loss reduction, CVR factors - provide intuitive validation of each study.

What do they think about ETAP?

Customer perspective

Combining DER and CVR provides a double boost in peak load reduction and overall loss minimization.

By Vivek A Jayaraman, Power Engineer, ETAP

 



Videos

Modeling and Verification of Benchmark Test Feeder Systems with DER in ETAP

Washington State University collaborates with IIT and ETAP on developing benchmark test feeder systems for the DOE UI-ASSIST project, showcasing ETAP's capabilities through the design and modeling of the IIT Rural Benchmark and modified IEEE 123-node systems, with validation conducted across MATLAB/SIMULINK and ETAP for various distribution studies.


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