The influence of a solid dielectric spacer on electron avalanches in nitrogen at atmospheric pressure

Jaksts, A.; Cross, J.D.

doi:10.1109/ceej.1981.6590829

Cited by 11 publications

(4 citation statements)

References 5 publications

(6 reference statements)

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“…From the above model introduction, it can be seen that the synergistic effect of adsorbed gas and charge on the insulating surface will affect all four processes, so it is extremely important for flashover research. The electron tail phenomenon observed by Jaksts [94,95] can gain new understanding from this synergy model. Zheng et al [96] further measured the thickness of the effective surface layer.…”

Section: 'Analogous Ineffective Region' Expansionmentioning

confidence: 91%

A review on factors that affect surface charge accumulation and charge-induced surface flashover

Yuan

Zou

et al. 2021

Nanotechnology

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The surface charge accumulation is very likely to trigger the surface flashover, which limits the large-scale application of DC GIL/GIS. This article comprehensively reviews the effect of six factors, including insulator-electrode shape, surface roughness of the insulator and conductor, metal particles, temperature, humidity, and gas type, on the insulator surface charging property. Furthermore, three models i.e. ‘analogous ineffective region’ expansion model, charge cluster triggered surface flashover model, and synergistic model of adsorbed gas, revealing the mechanism of charge triggered surface flashover phenomenon are reviewed and discussed. Future work from the perspective of theoretical analysis and engineering application are suggested in this field.

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Section: 'Analogous Ineffective Region' Expansionmentioning

confidence: 91%

A review on factors that affect surface charge accumulation and charge-induced surface flashover

Yuan

Zou

et al. 2021

Nanotechnology

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“…Photoemission from dielectrics in air (or nitrogen-oxygen mixtures) is less understood than photoemission from metals. The development of avalanches in the vicinity of some di electrics (polyethylene) in pure gases or in vacuum were studied in [43][44][45][46][47][48][49]. For the photons of 280-440 nm (SPS N 2 ), the photoemission yield is estimated as γ = − 10 7 , which is very small.…”

Section: The Uncertainty About the Photoemission Yieldmentioning

confidence: 99%

Pulsed positive discharges in air at moderate pressures near a dielectric rod

Dubinova¹,

Trienekens²,

Ebert³

et al. 2016

Plasma Sources Sci. Technol.

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We study pulsed positive discharges in air in a cylindrically symmetric setup with an electrode needle close (about 1 mm) above the top of a dielectric cylindrical rod of 4 mm in diameter mounted at its bottom on a grounded plate electrode. We present ICCD (intensified chargecoupled device) pictures and evaluations of experiments as well as simulations with a fluid discharge model; the simulations use cylindrical symmetry. In the experiments, there is an initial inception cloud phase, where the cylindrical symmetry is maintained, and later a streamer phase, where it is broken spontaneously. At 75-150 mbar, discharges with cylindrical symmetry are not attracted to the dielectric rod, but move away from it. The dielectric rod plays the sole role of an obstacle that shades (in the context of photoionization) a cone-shaped part of the inception cloud; the cone size is determined by the geometry of the setup. The material properties of the dielectric rod, such as its dielectric permittivity and the efficiency of the photon induced secondary electron emission do not have a noticeable effect. This is due to the abundance of photoionization in air, which supplies a positive discharge with free electrons and allows it to propagate along the electric field lines. Using some simple field calculations, we show that field enhancement due to dielectric polarization does not play a significant role in our geometry as long as the discharge maintains its cylindrical symmetry. The field component towards the rod is insufficiently enhanced to cause the discharge to move towards the rod. Any additional electrons produced by the dielectric surface do not influence this discharge morphology. This interpretation is supported by both experiments and simulations. At higher pressures (400-600 mbar) or for larger gaps between the needle and the dielectric rod, the inception cloud reaches its maximal radius within the gap between needle and rod and destabilizes there. In those cases, streamer channels are more likely to turn into a surface streamer. All our experiments and simulations were performed at moderate pressures (75-600 mbar), but we expect that the results will be the same for other pressures assuming that all the lengths scales (including the rod) in the setup are rescaled according to the Townsend scaling of the discharge.

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“…Jaksts and Cross [25] measured avalanches across polyethylene and Teflon insulators in N 2  In an N 2 gap without an insulator they measured a primary avalanche and secondary avalanches that originated from the cathode due to photoemission. In the bridged gap, they measured additional avalanches that they attributed to photoemission from the insulator surface initiated by photons from the primary avalanche from an excited state having a lifetime of 20  Both spacers gave similar results, indicating that the exciting mechanism was the same in the gas.…”

Section: Past Work In Literaturementioning

confidence: 99%

Surface interactions involved in flashover with high density electronegative gases.

Hodge¹,

Warne²,

Jorgenson³

et al. 2010

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This report examines the interactions involved with flashover along a surface in high density electronegative gases. The focus is on fast ionization processes rather than the later time ionic drift or thermalization of the discharge. A kinetic simulation of the gas and surface is used to examine electron multiplication and includes gas collision, excitation and ionization, and attachment processes, gas photoionization and surface photoemission processes, as well as surface attachment. These rates are then used in a 1.5D fluid ionization wave (streamer) model to study streamer propagation with and without the surface in air and in SF6. The 1.5D model therefore includes rates for all these processes. To get a better estimate for the behavior of the radius we have studied radial expansion of the streamer in air and in SF6. The focus of the modeling is on voltage and field level changes (with and without a surface) rather than secondary effects, such as, velocities or changes in discharge path. An experiment has been set up to carry out measurements of threshold voltages, streamer velocities, and other discharge characteristics. This setup includes both electrical and photographic diagnostics (streak and framing cameras). We have observed little change in critical field levels (where avalanche multiplication sets in) in the gas alone versus with the surface. Comparisons between model calculations and experimental measurements are in agreement with this. We have examined streamer sustaining fields (field which maintains ionization wave propagation) in the gas and on the surface. Agreement of the gas levels with available literature is good and agreement between experiment and calculation is good also. Model calculations do not indicate much difference between the gas alone versus the surface levels. Experiments have identified differences in velocity between streamers on the surface and in the gas alone (the surface values being larger).

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The influence of a solid dielectric spacer on electron avalanches in nitrogen at atmospheric pressure

Cited by 11 publications

References 5 publications

A review on factors that affect surface charge accumulation and charge-induced surface flashover

A review on factors that affect surface charge accumulation and charge-induced surface flashover

Pulsed positive discharges in air at moderate pressures near a dielectric rod

Surface interactions involved in flashover with high density electronegative gases.

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