Modelling vacuum flashover mitigation with complex surface microstructure: mechanism and application

Zhang, Shu; Sun, Guangyu; Mu, Hai‐Bao; Song, Bai‐Peng; Xue, Jie; Zhang, Guanjun

doi:10.1049/hve.2019.0363

Cited by 21 publications

(23 citation statements)

References 47 publications

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“…The insulation structure is fixed by electrodes such that the porous side and non-porous side are symmetrically located across the midplane (Figure 5a). Electrons passing through the pores enter a large vacuum zone and are unlikely to return to the surface, hence mitigating the formation of multipactor due to SE emission avalanche and improving the surface flashover threshold [47,48]. To verify this, flashover channels were observed 30 times for each sample to investigate the positions of flashover channels and their occurrence probabilities.…”

Section: Influence Of Cavity Structure On the Electric Field And Flas...mentioning

confidence: 99%

“…To provide more immediate evidence for the SEEA process suppression, the surface charging behaviour (i.e., surface potential distribution) of the representative insulation structures (i.e., non-porous surface, W1L3Q0.5, and W0.5L3Q0.5) after applying −30 kV impulse voltage with various pulse times N were investigated. When an insulation structure is subjected to a high applied voltage, the seed electrons emitted from the CTJ due to field emission are sufficiently accelerated by the parallel field and collide on the surface of the insulator with relatively high energy [47]. The process generates multipactor which propagates towards the anode in the form of SEEA.…”

Section: Surface Charging Behaviours In Vacuummentioning

confidence: 99%

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Design and 3D printing of porous cavity insulation structure for ultra‐high electrical withstanding capability

et al. 2023

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Vacuum‐dielectric interface is the most vulnerable part of vacuum insulation systems where surface electrical breakdown is prone to happen, hence severely restricts the development of advanced electro‐vacuum devices with large capacity and its miniaturisation. Generally, a direct and effective way to improve vacuum surface insulation is to alleviate the initiation and development of multipactor phenomena. Inspired by this approach, the authors report a 3D‐printed insulation structure designed with a millimetre‐scale surface cavity covered by periodic through‐pore array via stereolithography, exhibiting remarkable multipactor suppression and flashover threshold improvement, well outperforming the conventional flashover mitigation strategies. Experiments and simulations demonstrate that electrons in the multipactor region pass through‐pores and are unlikely to escape from the cavity, hence no longer participate in the above‐surface multipactor process, and eventually improve flashover threshold. The proposed approach provides new inspiration for the design of advanced insulators featuring ultra‐high electrical withstanding capability and brings up new insight into pertinent industrial applications.

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Section: Influence Of Cavity Structure On the Electric Field And Flas...mentioning

confidence: 99%

Section: Surface Charging Behaviours In Vacuummentioning

confidence: 99%

Design and 3D printing of porous cavity insulation structure for ultra‐high electrical withstanding capability

et al. 2023

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“…An injected energy of each lightning impulse voltage was approximately 10 kJ. The up‐and‐down method was used [9], and the Δ U was set to 2 kV. The breakdowns were calculated by observing the voltage waveforms on a digital oscilloscope.…”

Section: Experiments Setupmentioning

confidence: 99%

“…Many literatures reported the insulation performance of gaps between the centre shield and end shield in VIs [5][6][7][8][9]. Giere et al found that an optimal radius of the shield to gain the highest insulation performance [5].…”

Section: Introductionmentioning

confidence: 99%

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Breakdown of shield gaps in vacuum interrupters

Wang

Liu

et al. 2020

High Voltage

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The objective of this paper is to determine how the high-voltage discharging metal vapour deposited on the nearby ceramic inner surface influences the breakdowns of gaps between centre shield and end shield in vacuum interrupters. Two types of shield materials were selected, namely copper and stainless steel. The end curvature radius of the shield was 3 mm. The distance between the shields could adjust manually from 4 to 8 mm. The distance between the shields and ceramic was 3.5 mm. The negative polarity standard lightning impulse voltage (12/50 μs) was repeated for 900 operations based on an up-and-down method. The experimental results illustrated that the metal deposition layer on the inner surface of the ceramic envelope significantly influenced the breakdown voltage of the shield gaps. At a shield gap distance of d ¼ 4 mm, the breakdown voltage of the shield gap increased from an initial lower voltage to the saturation voltage by approximately 200 operations. Then, the breakdown voltage decreased to a lower voltage range during only 50 operations, and the breakdown voltage maintained at this lower voltage range until the end of 900 operations. Furthermore, as the shield gap distance increased from d ¼ 4 to 6 mm and 8 mm, the breakdown voltage also maintained at this lower voltage range. A metal deposition layer was formed on the inner surface of ceramic by repetitive application of the lightning impulse voltage. To analyse the influence of the metal deposition layer, the electric field distributions were calculated for the original vacuum interrupter and the vacuum interrupter with the metal deposition layer on the ceramic inner surface. The simulation results suggested that the metal deposition layer took part in the breakdown path between the shield gaps and deteriorated the insulation performance.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Tailoring Organic/Inorganic Interface Trap States of Metal Oxide/Polyimide toward Improved Vacuum Surface Insulation

Yang,

Sun,

Guo

et al. 2023

ACS Appl. Mater. Interfaces

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High-voltage and high-power devices are indispensable in spacecraft for outer space explorations, whose operations require aerospace materials with adequate vacuum surface insulation performance. Despite persistent attempts to fabricate such materials, current efforts are restricted to trial-and-error methods and a universal design guideline is missing. The present work proposes to improve the vacuum surface insulation by tailoring the surface trap state density and energy level of the metal oxides with varied bandgaps, using coating on a polyimide (PI) substrate, aiming for a more systematical workflow for the insulation material design. First-principle calculations and trap diagnostics are employed to evaluate the material properties and reveal the interplay between trap states and the flashover threshold, supported by dedicated analyses of the flashover voltage, secondary electron emission (SEE) from insulators, and surface charging behaviors. Experimental results suggest that the coated PI (i.e., CuO@PI, SrO@PI, MgO@PI, and Al2O3@PI) can effectively increase the trap density and alter the trap energy levels. Elevated trap density is demonstrated to always yield lower SEE. In addition, increasing shallow trap density accelerates surface charge dissipation, which is favorable for improving surface insulation. CuO@PI exhibits the most remarkable increase in shallow trap density, and accordingly, the highest flashover voltage is 42.5% higher than that of pristine PI. This study reveals the critical role played by surface trap states in flashover mitigation and offers a novel strategy to optimize the surface insulation of materials.

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Modelling vacuum flashover mitigation with complex surface microstructure: mechanism and application

Cited by 21 publications

References 47 publications

Design and 3D printing of porous cavity insulation structure for ultra‐high electrical withstanding capability

Design and 3D printing of porous cavity insulation structure for ultra‐high electrical withstanding capability

Breakdown of shield gaps in vacuum interrupters

Tailoring Organic/Inorganic Interface Trap States of Metal Oxide/Polyimide toward Improved Vacuum Surface Insulation

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