Energization, Voltage Magnification, and VFD Interaction Analysis
Shankar Ramharack and Rajiv Sahadeo
This repository contains the KESTREL EMT simulation files, Python post-processing scripts, and validation data accompanying the preprint(submitted to IEEE CaribCon 2026):
S. Ramharack and R. Sahadeo, "Validation of KESTREL EMT for Industrial Capacitor Switching Transient Studies: Energization, Voltage Magnification, and VFD Interaction Analysis," arXiv preprint arXiv:2602.17118, Feb. 2026. [PDF]
Electromagnetic transient (EMT) simulation is essential for analyzing sub-cycle switching phenomena in industrial power systems, yet commercial EMT platforms present significant cost barriers for smaller utilities, consultancies, and academic institutions—particularly in developing regions.
This work validates KESTREL EMT, a free electromagnetic transient solver with Python integration, through three progressive case studies of industrial capacitor switching transients at a medium-voltage (13.8 kV) industrial facility.
| Case | Description | Key Validation |
|---|---|---|
| 1 | Single capacitor bank energization | Frequency agreement within 1.2%, peak voltage within 3.9% vs. closed-form analytical solution |
| 2 | Voltage magnification through a Dyn transformer | 0.79× magnification factor; confirms transformer vector group influence on transient transfer |
| 3 | 6-pulse VFD interaction with utility capacitor bank | Demonstrates the "steady-state blind spot"—1.69 p.u. transient overvoltage invisible to load flow and harmonic scans |
The modeled system represents a typical medium-voltage industrial facility supplied from a utility substation with switched capacitor banks, including:
- Three-phase cosine voltage source (13.8 kV L-L RMS)
- Utility source impedance (series R-L)
- Switched capacitor bank at the utility bus
- Dyn step-down transformer supplying a facility bus
- Facility power factor correction capacitor bank
- 6-pulse variable frequency drive (VFD) load
| Metric | Analytical / Expected | KESTREL | Error |
|---|---|---|---|
| Oscillation frequency (Case 1) | — | — | 1.2% |
| Peak voltage (Case 1) | 2.0 p.u. | — | 3.9% |
| Peak current (Case 3) | — | — | 8.7% |
| Magnification factor (Case 2) | — | 0.79× | — |
| VFD transient overvoltage (Case 3) | — | 1.69 p.u. | — |
All validation errors are well within engineering tolerances for EMT studies.
When working with KESTREL EMT, pay attention to these implementation details documented in the paper:
- Voltage source scaling: KESTREL uses a "VLL RMS" convention for three-phase sources
- Dyn transformer specification: Turns ratio is specified on a per-phase peak-voltage basis
- VFD DC bus measurement: Requires differential measurement across the floating rectifier topology
- General principle: Always verify model parameters against known analytical solutions before conducting production EMT studies
@misc{ramharack2026validationkestrelemtindustrial,
title={Validation of KESTREL EMT for Industrial Capacitor Switching Transient Studies},
author={Shankar Ramharack and Rajiv Sahadeo},
year={2026},
eprint={2602.17118},
archivePrefix={arXiv},
primaryClass={eess.SY},
url={https://arxiv.org/abs/2602.17118},
}This project is licensed under the MIT License — see the LICENSE file for details.
- The KESTREL EMT development team for providing a free EMT solver
- IEEE PES Trinidad & Tobago Chapter
This work aims to lower the barrier to EMT analysis for engineers and researchers in developing regions by demonstrating validated, reproducible methodologies using freely available tools.