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Shaft Voltage and Current Phenomena in Turbo generators: Case Study of Post-Overhauling Bearing Anomaly at a 210 MW KWU Turbine Set: Case Study of Post-Overhauling Bearing Anomaly at a 210 MW KWU Turbine Set
Subject area: Science,Engineering and Technology · Area of research: Turbo generators
DOI: 10.64388/IREV9I12-1718555
Abstract
Shaft voltage and bearing currents represent critical reliability challenges for large-scale gubernators. Left unmanaged, these phenomena accelerate bearing degradation, trigger unplanned outages, and compromise machine longevity. This paper investigates the physical mechanisms of shaft voltage generation through a detailed case study of a 210 MW KWU-design turbine following a scheduled overhaul. By correlating electromagnetic, capacitive, magnetic, and electrostatic sources with field observations, this study proposes a robust framework of tiered operational thresholds. Findings indicate that voltages exceeding specific levels, when paired with leakage currents, serve as vital condition-monitoring indicators to prevent catastrophic failure The study demonstrates that voltages above certain level corelated with leakage currents can be an effective tool for condition monitoring, improving reliability and also preventing catastrophic failures. A framework of threshold zones is introduced, and future research recommendations include digital twins, AI-based predictive diagnostics, and advanced materials for grounding brushes. The findings support both immediate operational decision-making and longer-term design improvements for large synchronous machines [1,5&6].
Keywords
Shaft Voltage, Bearing Current, Electrical Discharge Damage, Grounding Brush, KWU Turbine, Turbogenerator Reliability.
References
[1] NEMA MG 1-2014, Motors & Generators, National Electrical Manufacturers Association, 2014.
[2] IEC 60034-25, Rotating Electrical Machines – Part 25, IEC, 2007.
[3] IEEE Std 115-2019, IEEE Guide for Test Procedures for Synchronous Machines, 2019.
[4] IEEE Std 112-2017, IEEE Standard Test Procedure for Polyphase Induction Motors and Generators, 2017.
[5] M. J. Prieto et al., 'Shaft Voltage and Bearing Currents in Turbomachinery: Mechanisms, Monitoring, and Mitigation,' Energies, vol. 14, no. 21, pp. 1–15, 2021.
[6] Comprehensive review of shaft voltages and bearing currents, Energies, 2025[1,5&6].
[7] [IEEE T-EC 1988] Ammann et al., “Shaft voltages in generators with static excitation systems—problems and solution,” IEEE Trans. Energy Conversion, 3(2):409–419.
[8] [IEEE T-PEL 1997] Busse/Erdman/Kerkman/Schlegel/Skibinski, “Bearing currents and their relationship to PWM drives,” IEEE Trans. Power Electronics, 12(2):243–252.
[9] [IEEE IAS 1997] Busse et al., “System electrical parameters and their effects on bearing currents,” IEEE Trans. Industry Applications, 33(2):577–584.
[10] Salazar et al., “Electrostatic enforcement of steam power plant,” IEEE IAS Annual Meeting, 2013.
[11] Mailula et al., “A Comprehensive Review of Shaft Voltages and Bearing Currents…,” Energies, 2025.
[12] [ABB Library] Technical Guide No. 5 – Bearing currents in modern AC drive systems.
[13] Desroches, “Investigation of Hydrogenator Vulnerability Regarding Shaft Voltage and Bearing Current,” IRMC 2023.
[14] [EASA] “Understanding Shaft Voltage & Grounding Currents of Turbine Generators.”
[15] “Electrostatic Discharge on a Large Steam Turbine Generator,” ORBIT Vol. 27 No. 2.
[16] [Zhao et al., “Electrostatic discharge impacts on the main shaft bearings of wind turbines,” Wind Energy Science, 2023.
[17] Kumar and S. Roy, 'Electrical Discharge Damage in Generator Bearings: A Review and Field Case Studies,' IEEE Trans. Energy Convers., vol. 37, no. 4, pp. 3124–3135, Dec. 2022
How to cite this paper
@article{1718555,
author = {Shobhan Kumar Malana, Suryabali},
title = {Shaft Voltage and Current Phenomena in Turbo generators: Case Study of Post-Overhauling Bearing Anomaly at a 210 MW KWU Turbine Set: Case Study of Post-Overhauling Bearing Anomaly at a 210 MW KWU Turbine Set},
journal = {Iconic Research And Engineering Journals},
year = {2026},
volume = {9},
number = {12},
pages = {73-81},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1718555.pdf},
abstract = {Shaft voltage and bearing currents represent critical reliability challenges for large-scale gubernators. Left unmanaged, these phenomena accelerate bearing degradation, trigger unplanned outages, and compromise machine longevity. This paper investigates the physical mechanisms of shaft voltage generation through a detailed case study of a 210 MW KWU-design turbine following a scheduled overhaul. By correlating electromagnetic, capacitive, magnetic, and electrostatic sources with field observations, this study proposes a robust framework of tiered operational thresholds. Findings indicate that voltages exceeding specific levels, when paired with leakage currents, serve as vital condition-monitoring indicators to prevent catastrophic failure The study demonstrates that voltages above certain level corelated with leakage currents can be an effective tool for condition monitoring, improving reliability and also preventing catastrophic failures. A framework of threshold zones is introduced, and future research recommendations include digital twins, AI-based predictive diagnostics, and advanced materials for grounding brushes. The findings support both immediate operational decision-making and longer-term design improvements for large synchronous machines [1,5&6].},
keywords = {Shaft Voltage, Bearing Current, Electrical Discharge Damage, Grounding Brush, KWU Turbine, Turbogenerator Reliability.},
month = {June},
doi = {https://doi.org/10.64388/IREV9I12-1718555}
}