Propagation of positive streamers over insulating surfaces in air

Allen, N.L.; Ghaffar, Asim

doi:10.1109/ceidp.1995.483759

Cited by 12 publications

(8 citation statements)

References 2 publications

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“…This effect has been attributed in [3] to the results of photo-emission of electrons from the insulator surface by UV light from the formative avalanches. It has been demonstrated by Gosho et al [12] and Verhaart et al [7] and proposed also as the reason for the higher velocities of streamers over insulating surfaces, compared with those in air [5]. However, there is a more rapid decay of the corona current, which is attributed to an electron current, indicated by the half-width measurements of Figure 8.…”

Section: Methodsmentioning

confidence: 49%

“…More recently, studies of the pre-breakdown discharges have attempted a more fundamental approach. Thus, the work of Gallimberti et al [3] and Windmar [4] in non-uniform field configurations and of Allen and colleagues [5,6] in uniform fields have attempted to display the properties of streamers when propagated along insulating surfaces. The basic properties of avalanches in proximity with insulating surfaces have been investigated by Verhaart and colleagues [7,8], providing valuable insights into the formative stages of corona on surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Progression of positive corona on cylindrical insulating surfaces. I. Influence of dielectric material

Tan

Allen

Rodrigo

2007

IEEE Trans. Dielect. Electr. Insul.

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Experiments are described on the propagation of corona discharges over the surfaces of cylindrical PTFE and porcelain insulators under positive impulse voltages. A rod-plane electrode arrangement has been used to which a single value of peak voltage, with the same impulse profile, has been applied throughout. Quantities measured were inception times and voltages, corona current and light output at selected axial regions of the corona. Still photographs of the corona appearance have been taken. Comparison has been made between the surface corona and that in air alone. Interpretation is based on knowledge of the electric field profiles, as modified by the insulators and the possible effects of the surface on the discharge. These are discussed in terms of the presence or absence of charge attachment, the effects of the surface on electron production and the effect of the permittivity of the materials.

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Section: Methodsmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Progression of positive corona on cylindrical insulating surfaces. I. Influence of dielectric material

Tan

Allen

Rodrigo

2007

IEEE Trans. Dielect. Electr. Insul.

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“…Most of the gathered knowledge comes from electrical engineers, who have been troubled by this phenomenon for years [2][3][4][5][6][7][8][9][10] because material interaction with the streamer development is of significance when it comes to insulation performance. For the most part, their research was done in air and in atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

“…Allen and Ghaffar [2] showed that the streamers usually propagate in two modes-there is a fast component over the dielectric surface and a slow one in ambient air. They offered an explanation, saying that the ionization rate was altered in the presence of an insulator because of electrons emitted from the dielectric surface by photoemission and detachment of negative ions.…”

Section: Introductionmentioning

confidence: 99%

Speed of streamers in argon over a flat surface of a dielectric

Sobota¹,

Lebouvier²,

Kramer³

et al. 2008

J. Phys. D: Appl. Phys.

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A pin–pin electrode geometry was used to study the velocities of streamers propagating over a flat dielectric surface and in gas close to the dielectric. The experiments were done in an argon atmosphere, at pressures from 0.1 to 1 bar, with repetitive voltage pulses. The dielectric surface played a noticeable role in discharge ignition and propagation. The average speed of the discharge decreased with higher pressure and lower voltage pulse rise rate. It was higher when the conductive channel between the electrodes was formed over the dielectric, rather than through the gas. Space resolved measurements revealed an increase in velocity of the discharge as it travelled towards the grounded electrode.

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“…Allen et al [13], [14], [15] studied the propagation of streamers across a parallel-plate air gap bridged by different solid insulators, 12 cm thick (insulator materials included Teflon, nylon and glazed ceramic). The streamer was formed by imposing a positive pulsed voltage on a point electrode located in a small aperture cut in the anode.…”

Section: Past Workmentioning

confidence: 99%

Effect of Dielectric Photoemission on Surface Breakdown: An LDRD Report

Jorgenson¹,

Warne²,

Neuber³

et al. 2003

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The research discussed in this report was conceived during our earlier attempts to simulate breakdown across a dielectric surface using a Monte Carlo approach. While cataloguing the various ways that a dielectric surface could affect the breakdown process, we found that one obvious effect -photoemission from the surface -had been ignored. Initially, we felt that inclusion of this effect could have a major impact on how an ionization front propagates across a surface because of the following argument chain: (1) The photon energy required to release electrons from a surface via photoemission is less than the photon energy required to ionize gas molecules directly. (2) The mean free path of a photon in gas is longer for low-energy photons than for high-energy photons. (3) Photoionization is a major effect in advancing the ionization front for breakdown in gas without a surface, therefore, we know that even high-energy photons can be released from the head of a streamer and propagate some distance through the gas. Our hypothesis, therefore, was that photons with energies near the threshold of photoemission could travel further in front of the streamer before being absorbed than higher-energy photons needed for photoionization, yet the lower-energy photons, with the help of the surface, could still create seed electrons for new avalanches. Thus, the streamer would advance more rapidly next to a surface than in gas alone. Additionally, the photoemission from the surface would add to the electrons in the avalanche and cause the avalanche to grow faster. After some study, however, we are forced to conclude that although photoemission does contribute to avalanche growth at fields near breakdown threshold, secondary electron emission causes electrons to stick to the surface and cancels out the growth due to photoemission. This conclusion assumes a discharge that occurs over a short period of time so that charging of the surface, which could alter its secondary electron emission characteristics, does not occur. This report documents the numerical work we did on investigating this effect and the experimental work we did on pre-breakdown phenomena in gas.

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Propagation of positive streamers over insulating surfaces in air

Cited by 12 publications

References 2 publications

Progression of positive corona on cylindrical insulating surfaces. I. Influence of dielectric material

Progression of positive corona on cylindrical insulating surfaces. I. Influence of dielectric material

Speed of streamers in argon over a flat surface of a dielectric

Effect of Dielectric Photoemission on Surface Breakdown: An LDRD Report

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