Destruction of the hydraulic unit shaft: Why it is possible?

Georgievskaia, Evgeniia

doi:10.1016/j.finmec.2021.100026

Cited by 5 publications

(6 citation statements)

References 14 publications

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“…leading to an increase in drivetrain torsional strain [11]- [13]. The Campbell diagram is a commonly used tool to show the interference points between the machine's airgap torque and shaft's natural frequencies [14].…”

Section: H Figure 1 a Single-line Diagram Of A Pumped Storage Hydropo...mentioning

confidence: 99%

“…The PWM modulation unit generates a switching function that is multiplied by the DC-link voltage [41]. Regardless of the operation mode of the machine, voltage, and current quantities can be written in a generic form in a steady state, as shown in (11) and ( 12) [42]: Where 𝜔 𝑘 is an arbitrary frequency (for example the PWM carrier frequency) and 𝜔 0 the fundamental frequency; ሺ𝑚 𝑣 , 𝑛 𝑣 ሻ and ሺ𝑚 𝑖 , 𝑛 𝑖 ሻ are arbitrary integer sets; 𝑉 𝑚 𝑣 𝑛 𝑣 and 𝐼 𝑚 𝑖 𝑛 𝑖 are the magnitudes of voltage and current. For a hreephase voltage system, 𝑣 𝑎 ሺ𝑡ሻ is the reference phase voltage.…”

Section: Vfd Switching Modelmentioning

confidence: 99%

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Variable Frequency Drives-Induced Torsional Stresses in Pumped Hydropower Storage Applications

Lingom,

Song-Manguelle,

Betoka-Onyama

et al. 2024

IEEE Access

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Despite consistent maintenance and monitoring equipment installed in pumped storage hydropower (PSH) facilities, many shafts and electrical component failures are reported, possibly resulting from undetected sources. These sources include undetectable vibrations or, in certain conditions, highfrequency mechanical or electrical harmonics. They may induce premature material fatigue and aging, leading to accelerated wear and premature system failure. This paper presents a direct method for plotting Campbell diagrams of large motors supplied by variable frequency drives for torsional analysis purposes. The method is applied to two-level, three-level neutral-point clamped, and seven-level cascaded H-bridge multilevel inverters, commonly used industrially available voltage source inverter (VSI) topologies for pumped PSH plants. These diagrams display the locations where torsional stress components induced by VFDs can interfere with shaft resonance modes. These locations are where threatening torsional stresses can build up. The method simplifies the determination of the magnitude of stimulus forces in the motor airgap that may threaten the shaft. An analytical assessment of the cascaded H-bridge VFD-induced torsional stresses under unbalanced operation is also proposed. The accuracy of the theoretical developments is supported by selected simulations results at different operating points and different fault conditions. Hybrid experimental-numerical VFD-induced harmonic stress analysis is also performed to demonstrate the relevance of the proposed study. Results are crucial for a robust design of the system integration to avoid catastrophic failures.

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Section: H Figure 1 a Single-line Diagram Of A Pumped Storage Hydropo...mentioning

confidence: 99%

Section: Vfd Switching Modelmentioning

confidence: 99%

Variable Frequency Drives-Induced Torsional Stresses in Pumped Hydropower Storage Applications

Lingom,

Song-Manguelle,

Betoka-Onyama

et al. 2024

IEEE Access

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“…Unexpected failure of such a component would result in inevitable power cuts and associated financial losses, huge repair/replacement costs and potential safety and environmental hazards. Several accidents of hydropower generation shaft failures have been reported in the literature (Georgievskaia, 2021; Momčilović et al ., 2012; Bhaumik et al ., 2002). In this respect, investigating each and every accident, in as much as it is an unfortunate event, is also an opportunity to expand the knowledge base as to why these accidents happen, on one hand, and, on the other hand, a means of preventing such failures in the future.…”

Section: Introductionmentioning

confidence: 99%

“…Hydropower generation is a major source for renewable energy and electric power currently obtained through hydropower generation stations accounts for nearly 75% of total renewable energy worldwide (Georgievskaia, 2021). The hydro-generation shaft is the main element that connects the generator unit to the water turbine; the main source of hydropower.…”

Section: Introductionmentioning

confidence: 99%

“…Data availability: The datasets generated during and/or analyzed during the current study are not publicly available due to need in further future publication but are available from the corresponding author on reasonable request. renewable energy worldwide (Georgievskaia, 2021). The hydro-generation shaft is the main element that connects the generator unit to the water turbine; the main source of hydropower.…”

mentioning

confidence: 99%

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Effects of non-symmetric non-uniformly distributed welding residual stress on fatigue failure initiation and propagation in a hydropower generator shaft

Jawwad

Mahdi

2023

MMMS

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PurposeThis article aims to investigate and model the effects of welding-generated thermal cycle on the resulting residual stress distribution and its role in the initiation and propagation of fatigue failure in thick shaft sections.Design/methodology/approachExperimental and numerical techniques were applied in the present study to explore the relationship(s) between welding residual-stress distribution and fatigue failure characteristics in a hydropower generator shaft. Experimental techniques included stereomicroscopy, optical and scanning electron microscopy (SEM), chemical analysis and mechanical testing. Finite element modelling (FEM) was used to model the shaft welding cycle in terms of thermal (temperature) history and the associated development of residual stresses within the weld joint.FindingsExperimental analyses have confirmed the suitability of the used material for the intended application and confirmed the failure mode to be low cycle fatigue. The observed failure characteristics, however, did not match with the applied loading in terms of design stress levels, directionality and expected crack imitation site(s). FEM results have revealed the presence of a sharp stress peak in excess of 630 MPa (about 74% of material's yield strength) around weld start point and a non-uniform residual stress distribution in both the circumferential and through-thickness directions. The present results have shown very close matching between FEM results and observed failure characteristics.Practical implicationsThe present article considers an actual industrial case of a hydropower generator shaft failure. Present results are valuable in providing insight information regarding such failures as well as some preventive design and fabrication measures for the hydropower and other power generation and transmission sector.Originality/valueThe presence of the aforementioned stress peak around welding start/end location and the non-uniform distribution of residual-stress field are in contrast to almost all published results based on some uniformity assumptions. The present FEM results were, however, the only stress distribution scenario capable of explaining the failure considered in the present research.

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The role of numerical simulation of fatigue crack growth in failure analysis of a turbine shaft

Milovanović,

Sedmak,

Grbović

et al. 2025

Engineering Failure Analysis

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Destruction of the hydraulic unit shaft: Why it is possible?

Cited by 5 publications

References 14 publications

Variable Frequency Drives-Induced Torsional Stresses in Pumped Hydropower Storage Applications

Variable Frequency Drives-Induced Torsional Stresses in Pumped Hydropower Storage Applications

Effects of non-symmetric non-uniformly distributed welding residual stress on fatigue failure initiation and propagation in a hydropower generator shaft

The role of numerical simulation of fatigue crack growth in failure analysis of a turbine shaft

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