Optimization of the Electric Field Distribution at the End of the Stator in a Large Generator

Hu, Haitao; Zhang, Xiaohong; Li, Yanli; Guo, Lingling; Gao, Junguo

doi:10.3390/en11102510

Cited by 8 publications

(3 citation statements)

References 21 publications

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“…Severe electric field distortion can result in corona discharge of the motor. Extensive research has been conducted to optimize the electric field intensity at this critical interface [9,10]. Therefore, it is important to develop efficient anti-corona materials.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Conductivity and Thermal Stability of Anti-Corona Epoxy Resin Nanocomposites

Liu,

Gao,

Guo

et al. 2024

Polymers

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The long-term operation of motors induces substantial alterations in the surface conductivity and nonlinear coefficient of anti-corona paint, diminishing its efficacy and jeopardizing the longevity of large motors. Hence, the development of high-performance anti-corona paint holds paramount importance in ensuring motor safety. In this study, we integrate two nano-fillers, namely silicon carbide (SiC) and organic montmorillonite (O-MMT), into a composite matrix comprising micron silicon carbide and epoxy resin (SiC/EP). Subsequently, three distinct types of anti-corona paint are formulated: SiC/EP, Nano-SiC/EP, and O-MMT/SiC/EP. Remarkably, O-MMT/SiC/EP exhibits a glass transition temperature about 25 °C higher than that of SiC/EP, underscoring its superior thermal properties. Moreover, the introduction of nano-fillers markedly augments the surface conductivity of the anti-corona paint. Aging tests, conducted across varying temperatures, unveil a notable reduction in the fluctuation range of surface conductivity post-aging. Initially, the nonlinear coefficients exhibit a declining trend, succeeded by an ascending trajectory. The O-MMT/SiC/EP composite displays a maximum nonlinearity coefficient of 1.465 and a minimum of 1.382. Furthermore, the incorporation of nanofillers amplifies the dielectric thermal stability of epoxy resin composites, with O-MMT/SiC/EP showcasing the pinnacle of thermal endurance. Overall, our findings elucidate the efficacy of nano-fillers in enhancing the performance and longevity of anti-corona paint, particularly highlighting the exceptional attributes of the O-MMT/SiC/EP composite in bolstering motor safety through improved thermal stability and electrical properties.

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Section: Introductionmentioning

confidence: 99%

Nonlinear Conductivity and Thermal Stability of Anti-Corona Epoxy Resin Nanocomposites

Liu,

Gao,

Guo

et al. 2024

Polymers

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“…A high switching frequency with a steep voltage rise (dU/dt) results in considerably higher electric field levels and possible Joule heating [8], [9], [15], [16]. This implies that possible degradation and failure mechanisms are thermal hots spots [2], [17], surface corona discharge at local points with high electric field [15], [18], or degradation of the stress relief coating due to high temperature [4], [9]. The effect of high frequency square voltage waveforms on the field grading has been studied in e.g.…”

Section: Introductionmentioning

confidence: 99%

Frequency Dependence of the Electric Field Grading of End-Winding of Generator Bars

Aakre

Enoksen

Eberg

et al. 2023

IEEE Trans. Dielect. Electr. Insul.

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To reduce the electric field stresses in the endwinding in hydropower generator bars, a field dependent grading tape is applied in the transition zone from outer corona protection to bare insulation. The design is typically optimized for 50/60 Hz with both low heat generation and optimal electric field distribution. The introduction of power electronic converters with high switching frequencies and dU/dt for controlling the generators changes the optimal design requirements. This work investigated experimentally the effect of higher voltage-frequencies on the conductivity in three field grading tapes from the same manufacturer with different field grading properties. The experimentally determined material parameters were then applied as inputs to finite element method (FEM) models to evaluate the electric field distribution at different voltage-frequencies. Measurements showed that the DC conductivity was highly nonlinear and strongly dependent on the electric field. This strong nonlinearity decreased at low electric fields as the frequency increased. The AC conductivity had a transition from a strong nonlinear material at line frequency to a less nonlinear material at 10 kHz. Simulations of the surface electric field and temperature using the DC conductivity for different voltage frequencies showed minor differences from simulations using the apparent AC conductivity. This indicates that the low field conductivity is of minor importance as it varied by two decades between DC and 10 kHz without resulting in a significant difference in either electric field, or temperature. The measured and simulated surface temperature increased linearly with applied voltage frequency. The simulated surface electric field was well distributed at line frequency, whereas it was greatly enhanced above 1 kHz.

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“…High-conductivity composites with constant parameters can effectively improve the field concentration phenomenon. However, the application of high conductivity composites is limited by the problems of large leakage current, and the inability to apply a single parameter to parts with large differences in electric field values for these materials [9,10]. Therefore, the use of composite materials with nonlinear conductivity properties to improve the field concentration problem has gradually become a research focus.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Surface Conductivity Characteristics of Epoxy Resin-Based Micro-Nano Structured Composites

Guo

Sun

et al. 2022

Energies

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Nonlinear composite materials serve to homogenize electric fields and can effectively improve the local concentration of the electric field in power systems. In order to study the nonlinear surface conductivity properties of micro-nano epoxy composites, two types of epoxy micro-nano composite specimens were prepared in the laboratory using the co-blending method. The surface conductivity of the composites was tested under different conditions using a high-voltage DC surface conductivity test system. The results show that the surface conductivity of micro-nano structured composites increases and then decreases with the rise of nanofiller doping concentration. The nonlinear coefficient was 1.781 at 4 wt% of doped nanostructured SiC, which was the most significant nonlinear coefficient compared to other doping contents. For the same doping concentration, the micro-nano structured composites doped with nanostructured SiC have more significant surface conductivity at the same test temperature with a nonlinear coefficient of 1.635. As the temperature increases, the surface conductivity of the micro-nano structured composite increases significantly, and the threshold field strength moves towards the high electric field. Along with the increase in temperature, the nonlinear coefficients of micro-nano composites after doping with nanostructured SiC showed a gradually decreasing trend. The temperature has little effect on the nonlinear coefficients of the micro-nano structured composites after doping with O-MMT.

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Optimization of the Electric Field Distribution at the End of the Stator in a Large Generator

Cited by 8 publications

References 21 publications

Nonlinear Conductivity and Thermal Stability of Anti-Corona Epoxy Resin Nanocomposites

Nonlinear Conductivity and Thermal Stability of Anti-Corona Epoxy Resin Nanocomposites

Frequency Dependence of the Electric Field Grading of End-Winding of Generator Bars

Nonlinear Surface Conductivity Characteristics of Epoxy Resin-Based Micro-Nano Structured Composites

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