Potential distribution on the stress grading system of high-voltage rotating machines –I measuring system

Kumada, Akiko; Nakamura, Takahiro; Hidaka, Kunihiko; Tsuboi, Yoshikatsu; Yoshimitsu, Tetsuo

doi:10.1109/tdei.2015.005581

Cited by 18 publications

(11 citation statements)

References 7 publications

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“…The bar was cured in a hot press to give it its final dimension. impedance, and large frequency bandwidth, which permits to accurately measure the surface potential with minimum distortion [9]. However, this EO method only allows to determine the tangential E-field component (Et) by inverse calculation.…”

Section: Model Of the Stator Barmentioning

confidence: 99%

“…Such information can be of great interest to characterize the efficiency of the SGCs and reduce the E-field strength below the dielectric rigidity of the surrounding medium. In addition, this information is helpful to validate the different numerical simulations dedicated to SGC modelling where generally only Et is verified due to the restrictions of the experimental measurement methods [1, 9,10].…”

Section: Model Of the Stator Barmentioning

confidence: 99%

“…This method is well adapted for on-site inspection or as a complementary method for laboratory investigation involving potential and E-field surface measurements. For several years, potential surface measurement has been the most used method to assess the efficiency of SGCs [7][8][9]. The knowledge of the surface potential distribution permits to determine, by inverse calculation, the distribution of the tangential component of the E-field.…”

Section: Introductionmentioning

confidence: 99%

“…In order to provide less intrusive and more accurate potential measurements, the use of electrooptic (EO) sensors based on the Pockels effect was recently proposed and investigated [9]. The main advantages of the proposed EO sensor lies in the absence of metallic components, high input From on-site and laboratory investigation, several operational problems on HV generators have been reported [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…In order to provide less intrusive and more accurate potential measurements, the use of electro-optic (EO) sensors based on the Pockels effect was recently proposed and investigated [9]. The main advantages of the proposed EO sensor lies in the absence of metallic components, high input impedance, and large frequency bandwidth, which permits to accurately measure the surface potential with minimum distortion [9]. However, this EO method only allows to determine the tangential E-field component (E t ) by inverse calculation.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation of the Spatial and Temporal Evolution of the Tangential and Normal E-Field Components along the Stress Grading System of a Real Stator Bar

et al. 2020

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This paper presents results based on direct experimental measurements of tangential (Et) and normal (En) E-field components along the stress grading system (SGS) of a real stator bar (Roebel type) for different AC 60 Hz applied voltages. These measurements were made with a new electro-optic system allowing for the study of both spatial distributions of two E-field components along the bar and their temporal evolution at critical points. The results obtained allowed us to calculate the correlation between the distribution of En and Et along the SGS. In particular, it was demonstrated that the En distribution presents a characteristic minimum, which can be used to identify the zone of partial discharge inception. Moreover, it was possible to observe an enlargement of the Et component distribution followed by a saturation in magnitude with the applied voltage increase. Moreover, the results have demonstrated that the waveform of the En component is mostly affected by the SG material used, producing a greater distortion in its waveform than those obtained for the Et component. The more significant distortion was obtained at the end of the outer corona protection (OCP) material, corresponding to the first maximum of the En component and characterized by the appearance of a third harmonic of large amplitude.

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Section: Model Of the Stator Barmentioning

confidence: 99%

Section: Model Of the Stator Barmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Experimental Investigation of the Spatial and Temporal Evolution of the Tangential and Normal E-Field Components along the Stress Grading System of a Real Stator Bar

et al. 2020

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Experiment of electrothermal stress for different types of end turn grading in the inverter‐fed form‐wound windings

Zhao,

Wang,

Zhu

et al. 2024

High Voltage

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End turn grading with resistive–capacitive coupling experiences severe electrothermal stress when subjected to pulse width modulation (PWM) voltage. In this paper, several experiments and simulations were carried conducted for four types of end turn grading. First of all, the temperature rise in the end turn grading increased with a decrease in rise time. When the rise time was less than 500 ns, the temperature rise at the terminal was higher owing to the increased capacitive current coupled from the main wall insulation. Further, the current in the linear region exhibited minimal variation at different fundamental frequencies resulting in synchronized the temperature rise at the terminal and overlap. Furthermore, the jump voltage was the key factor influencing temperature rise in end turn grading, confirmed by comparing different voltage magnitudes. Finally, the transient behaviour of the maximum field in the stress grading material was determined at rise time. The experimental and simulation results indicate that balancing and interdependently addressing the electrical and thermal stress protection in end turn grading is crucial. The study aims to provide an experimental and theoretical foundation for an insulation system of inverter‐fed rotating machinery operating under PWM voltage.

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Experimental study of transient surface charging during dielectric barrier discharges in air gap in needle-to-plane geometry

Yang

Wang

et al. 2023

J. Phys. D: Appl. Phys.

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Motivated by a deeper understanding of plasma-surface interactions, this study presents experimental investigations into the transient surface charging process during dielectric barrier discharges (DBDs) in an air gap in a needle-to-plane geometry based on a combination of the Pockels method and a custom-designed ultrafast multi-frame imaging system. We realized three-frame observations of transient surface charge distributions, with a remarkable temporal resolution of 3 ns, during positive primary discharges and negative reverse discharges when applying a positive square-wave pulse. During the positive primary discharges at the rising voltage front, following the circular expansion of the streamer over the surface, multiple streamer filaments bifurcate simultaneously from the center, resulting in a branched positive surface charge distribution. Gradient surface charge densities are observed along the channel with higher charge densities at the head, which gradually evolve into a uniform distribution along the channel as the streamers approach stagnation. No lateral expansion of positive charges is observed across the channel under the present condition. In the case of negative reverse discharges occurring at the falling edge of the voltage pulse, the neutralization of residual positive surface charges and the accumulation of negative surface charges occur simultaneously in the central region. The deposited negative surface charges exhibit a progressively expanding circular distribution characterized by increasing charge density and radius. The propagation dynamics of surface streamers and the fields induced by surface charges are investigated and discussed based on the spatio-temporal surface charge measurements. Further study suggests that the surface streamer is not driven by the over-accumulation of surface charges, but rather by the space charge field above the dielectric. The presented quantitative measurements can be used for detailed validation of DBD simulations and offer deeper insights into plasma-surface interactions.

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Potential distribution on the stress grading system of high-voltage rotating machines –I measuring system

Cited by 18 publications

References 7 publications

Experimental Investigation of the Spatial and Temporal Evolution of the Tangential and Normal E-Field Components along the Stress Grading System of a Real Stator Bar

Experimental Investigation of the Spatial and Temporal Evolution of the Tangential and Normal E-Field Components along the Stress Grading System of a Real Stator Bar

Experiment of electrothermal stress for different types of end turn grading in the inverter‐fed form‐wound windings

Experimental study of transient surface charging during dielectric barrier discharges in air gap in needle-to-plane geometry

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