Pulsed flashover across a solid dielectric in vacuum

Zhang, Guanjun; Su, Guanghui; Song, Bai‐Peng; Mu, Hai‐Bao

doi:10.1109/tdei.2018.007133

Cited by 64 publications

(32 citation statements)

References 152 publications

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“…This means that in the process of thermal aging of long chains breaking into short chains, as the group changes, shallow traps gradually transform into deep traps, which is detrimental to charge dissipation. [31,33,34] The deep trap density and energy level at 35 days of aging are both the highest, which is the least conducive to the dissipation of electric charges, which is consistent with the dissipation results obtained in Figure 8.…”

Section: Charge Dissipation and Trap Distributionsupporting

confidence: 89%

Thermal‐aging characteristics of epoxy/glass fiber composite materials fordry‐typeair‐core reactors

Bian

Xia

et al. 2021

Polymer Composites

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In recent years, dry-type air-core reactors have frequently experienced inter-turn short circuits due to the aging of the inter-turn insulation. In this paper, we prepared epoxy/glass fiber samples and carried out an accelerated thermal aging test up to 840 hours. In different stages of aging, we tested the surface insulation properties, dielectric properties, thermal and mechanical properties of the samples. The results show that: Flashover voltage drops significantly, and when aging for 35 days, it has dropped by 12.4%. This is because aging is accompanied by the conversion of shallow traps to deep traps and the reduction of conductive channels, which slows down the charge dissipation rate and decreases the flashover voltage. Dielectric, thermal, and mechanical properties also show a deteriorating trend. Through the analysis of the changes in thermal and mechanical properties, it is inferred that thermal aging will damage the epoxy matrix more than the glass fiber. In addition, combined with the scanning electron microscope, Fourier transform infrared spectrometer, and X-ray photoelectron spectrometer characterization results, we believed that the main reason for the material deterioration is the detachment of the glass fiber and the break of the long chain of the matrix. This article has certain reference value for the subsequent engineering application and online monitoring of this material.

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Section: Charge Dissipation and Trap Distributionsupporting

confidence: 89%

Thermal‐aging characteristics of epoxy/glass fiber composite materials fordry‐typeair‐core reactors

Bian

Xia

et al. 2021

Polymer Composites

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“…[7,10,11,12,13,14,15]. Studies on the interaction between plasmas and dielectrics have often been performed at lower pressure and in noble gases, where the discharge mechanisms are relatively well understood [16,17]. Several authors have also studied surface discharges in atmospheric air.…”

Section: Introductionmentioning

confidence: 99%

A computational study of positive streamers interacting with dielectrics

Li,

Sun,

Zhang

et al. 2019

Preprint

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We use numerical simulations to study the dynamics of surface discharges, which are common in high-voltage engineering. We simulate positive streamer discharges that propagate towards a dielectric surface, attach to it, and then propagate over the surface. The simulations are performed in air with a two-dimensional plasma fluid model, in which a flat dielectric is placed between two plate electrodes. Electrostatic attraction is the main mechanism that causes streamers to grow towards the dielectric. Due to the net charge in the streamer head, the dielectric gets polarized, and the electric field between the streamer and the dielectric is increased. Compared to streamers in bulk gas, surface streamers have a smaller radius, a higher electric field, a higher electron density, and higher propagation velocity. A higher applied voltage leads to faster inception and faster propagation of the surface discharge. A higher dielectric permittivity leads to more rapid attachment of the streamer to the surface and a thinner surface streamer. Secondary emission coefficients are shown to play a modest role, which is due to relatively strong photoionization in air. In the simulations, a high electric field is present between the positive streamers and the dielectric surface. We show that the magnitude and decay of this field are affected by the positive ion mobility.

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“…The surface flashover voltage is much lower than the vacuum (or gas) breakdown voltage or the solid breakdown voltage at the same electrode distance, reducing the withstand voltage capability and damaging the safe and stable operation of electrical systems. Eventually, not only the power energy storage and transmission but also the economy will be affected negatively [1][2][3][4]. It is an important factor making components prone to failure in lowvoltage systems [5].…”

Section: Introductionmentioning

confidence: 99%

Improvement of surface flashover in vacuum

2020

High Voltage

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Surface flashover of insulation systems is a basic issue in the field of high voltage and electrical insulation. To improve the surface flashover performance is of great significance for the development of advanced power transmission equipment and insulation materials. This study reviews the research progress of surface flashover in vacuum regarding to effective methods to improve the surface flashover performance in vacuum, including insulation system optimisation and material modification. The former one is beneficial to reduce the electric field distortion, and the later one is able to adjust the surface trap parameters of the material through physical and chemical methods. In addition, the 'U-shaped' curve is proposed to reveal the relationship between surface flashover voltage and surface trap level, discovering the synthetic effects of surface traps on surface flashover. It is expected that the 'U-shaped' curve will become a guidance to improve surface flashover performance through adjusting trap parameters. Moreover, several suggestions are made to build unified surface flashover model which is suitable to the range from high vacuum to high pressure.

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Pulsed flashover across a solid dielectric in vacuum

Cited by 64 publications

References 152 publications

Thermal‐aging characteristics of epoxy/glass fiber composite materials fordry‐typeair‐core reactors

Thermal‐aging characteristics of epoxy/glass fiber composite materials fordry‐typeair‐core reactors

A computational study of positive streamers interacting with dielectrics

Improvement of surface flashover in vacuum

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