Methodology for Assessing Voltage–Reactive Power Capability of Synchronous Units under Modified Transformer Impedance
Keywords:
reactive capability, transformer impedance, per-unit modeling, SIM-Operating Map
Abstract
This paper presents a methodology for evaluating the voltage–reactive power capability of synchronous generators following changes in transformer impedance. The framework integrates per-unit calculations, an equivalent generator–transformer model, and numerical simulations across multiple grid-voltage scenarios. The SIM-Operating Map application provides analytical and graphical verification of reactive margins, limiting factors, and grid-code compliance, supporting operational decision-making and enhancing system security after transformer replacement.
References
[1] ENTSO-E, Network Code on Requirements for Generators (RfG), Regulation (EU) 2016/631, Brussels, 2016.
[2] ENTSO-E, Implementation Guidance Document: Compliance Monitoring after Operational Notification, Brussels, 2018.
[3] ENTSO-E, System Operation Guideline (SO GL), Brussels, 2017.
[4] IEEE Standard 421.5-2016, IEEE Recommended Practice for Excitation System Models for Power System Stability Studies, IEEE PES, New York, 2016.
[5] NERC, Reliability Guideline – Reactive Power Planning, Atlanta, 2017.
[6] IEEE Power System Relaying Committee (PSRC), Voltage Collapse Mitigation: Analytical Approaches and Protection Considerations, IEEE Report, 2015.
[7] T. J. Overbye, M. L. Crow, and J. D. Weber, “Modeling Generator Step-Up Transformer Status for Reactive Loss Analysis,” IEEE Trans. on Power Systems, vol. 33, no. 4, pp. 4128–4136, 2018.
[8] S. Øyvang, H. Gjengedal, and L. Hofmann, “Online Monitoring of Synchronous Generator Capability Curves,” Electric Power Systems Research, vol. 157, pp. 88–95, 2018.
[9] CIGRE Working Group C4/C1.25, Reactive Power Capability Verification and Grid Code Compliance, CIGRE Technical Brochure No. 791, Paris, 2020.
[10] Energy Systems Integration Group (ESIG), Reactive Power Capability and Interconnection Requirements, Technical Report, Charlottesville, VA.
[2] ENTSO-E, Implementation Guidance Document: Compliance Monitoring after Operational Notification, Brussels, 2018.
[3] ENTSO-E, System Operation Guideline (SO GL), Brussels, 2017.
[4] IEEE Standard 421.5-2016, IEEE Recommended Practice for Excitation System Models for Power System Stability Studies, IEEE PES, New York, 2016.
[5] NERC, Reliability Guideline – Reactive Power Planning, Atlanta, 2017.
[6] IEEE Power System Relaying Committee (PSRC), Voltage Collapse Mitigation: Analytical Approaches and Protection Considerations, IEEE Report, 2015.
[7] T. J. Overbye, M. L. Crow, and J. D. Weber, “Modeling Generator Step-Up Transformer Status for Reactive Loss Analysis,” IEEE Trans. on Power Systems, vol. 33, no. 4, pp. 4128–4136, 2018.
[8] S. Øyvang, H. Gjengedal, and L. Hofmann, “Online Monitoring of Synchronous Generator Capability Curves,” Electric Power Systems Research, vol. 157, pp. 88–95, 2018.
[9] CIGRE Working Group C4/C1.25, Reactive Power Capability Verification and Grid Code Compliance, CIGRE Technical Brochure No. 791, Paris, 2020.
[10] Energy Systems Integration Group (ESIG), Reactive Power Capability and Interconnection Requirements, Technical Report, Charlottesville, VA.
Published
2025/12/29
Section
Original Scientific Paper