Optical diagnostics of liquid nitrogen volume pre-breakdown events

Butcher, M.; Neuber, A.; Krompholz, H.; Dickens, J.

doi:10.1109/ppc.2003.1277987

Cited by 12 publications

(4 citation statements)

References 7 publications

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“…Such microbubbles are likely to be randomly scattered throughout the bulk of the liquid volume, and also be present at the electrode surfaces. That microbubbles (or low-density localized regions) are responsible for the streamer formation and breakdown initiation is consistent with the observations of streamer development in oil where discrete optical luminosity spots have been seen on streamer branches [46]. Microbubbles were also considered by Gavrilov et al [33] as a possible cause for the observed dentritic structure of subsonic streamers in water.…”

Section: Discussionsupporting

confidence: 82%

Electrical breakdown of water in microgaps

Schoenbach

Kolb

Xiao

et al. 2008

Plasma Sources Sci. Technol.

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Experimental and modeling studies on electrical breakdown in water in submillimeter gaps between pin and plane electrodes have been performed. Prebreakdown, breakdown and recovery of the water gaps were studied experimentally by using optical and electrical diagnostics with a temporal resolution on the order of one nanosecond. By using Mach-Zehnder interferometry, the electric field distribution in the prebreakdown phase was determined by means of the Kerr effect. Electric fields values in excess of the computed electric fields, which reach >4 MV cm −1 for applied electrical pulses of 20 ns duration, were recorded at the tip of the pin electrode, an effect which can be explained by a reduced permittivity of water at high electric fields. Breakdown of the gaps, streamer-to-arc transition, was recorded by means of high-speed electrical diagnostics, and through high-speed photography. It was shown, through simulations, that breakdown is initiated by field emission at the interface of preexisting microbubbles. Impact ionization within the micro-bubble's gas then contributes to plasma development. Experiments using pulse-probe methods and Schlieren diagnostics allowed us to follow the development of the disturbance caused by the breakdown over a time of more than milliseconds and to determine the recovery time of a water switch. In order to trigger water switches a trigger electrode with a triple point has been utilized. The results of this research have found application in the construction of compact pulse power generators for bioelectric applications.

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Section: Discussionsupporting

confidence: 82%

Electrical breakdown of water in microgaps

Schoenbach

Kolb

Xiao

et al. 2008

Plasma Sources Sci. Technol.

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“…͑i͒ A distinct polarity effect is seen for point-plane ͑or similarly asymmetric͒ geometries. 1, 10,27,28 The breakdown voltage ͑=V br ͒ is universally observed to be lower when the point electrode is biased positively. Based on gas discharge physics, one might expect liquid water breakdown to be initiated at the cathode due to possible electronic injection.…”

Section: Introductionmentioning

confidence: 99%

“…2 have been reported elsewhere. 28 ͑iv͒ External pressure appears to affect the breakdown voltage. Increasing the overpressure typically tends to enhance the breakdown voltage, while underpressures have been observed to decrease the breakdown voltage.…”

Section: Introductionmentioning

confidence: 99%

Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

Qian

Joshi

Kolb

et al. 2005

Journal of Applied Physics

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An electrical breakdown model for liquids in response to a submicrosecond (∼100ns) voltage pulse is presented, and quantitative evaluations carried out. It is proposed that breakdown is initiated by field emission at the interface of pre-existing microbubbles. Impact ionization within the microbubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. Continuous field emission at the streamer tip contributes to filament growth and propagation. This model can adequately explain almost all of the experimentally observed features, including dendritic structures and fluctuations in the prebreakdown current. Two-dimensional, time-dependent simulations have been carried out based on a continuum model for water, though the results are quite general. Monte Carlo simulations provide the relevant transport parameters for our model. Our quantitative predictions match the available data quite well, including the breakdown delay times and observed optical emission.

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“…Denat et al carried out corona discharge studies in LN 2 and have observed vapor bubble formation near the high divergent electric field zone initiating multiple discharges in the bubbles formed. Butcher et al adopted optical technique for identification of incipient discharge process in liquid nitrogen and have identified that the current pulses generated are of nano second current pulses. This current pulses generates UHF signals in range 300–3000 MHz are excited .…”

Section: Introductionmentioning

confidence: 99%

Understanding surface discharge activity with epoxy silicon carbide nanocomposites

Sarathi

Sahoo

Chen

et al. 2017

Polymer Engineering & Sci

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Surface discharge inception voltage (SDIV) with epoxy silicon carbide nanocomposite material in LN 2 medium is about three times higher than that in air. Under AC voltage that SDIV increases with increase in wt% of silicon carbide (SIC) material in epoxy nanocomposites. Dielectric measurements indicates an increase in temperature of the specimen and the weight percentage of SIC filler in epoxy resin increases the permittivity of the material. Also, irrespective of percentage of SiC in epoxy resin, the tan(d) reduces with increase in frequency and the converse at room temperature. The UHF signal measured during surface discharge activity in air/LN 2 medium has frequency content in the range of 0.5-1.5 GHz. The charge decay characteristics of epoxy SiC nanocomposites indicate the deposited charge is less and the charge decay time reduces with increase in wt% of SiC in epoxy resin. The surface roughness caused due to surface discharge activity is high under negative DC voltage compared with positive DC/AC voltage. The phase resolved partial discharge (PRPD) analysis indicates discharges occur at the near peak of the AC voltage on inception of surface discharge and at higher stress it appears at the rising portion of AC voltage.

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Optical diagnostics of liquid nitrogen volume pre-breakdown events

Cited by 12 publications

References 7 publications

Electrical breakdown of water in microgaps

Electrical breakdown of water in microgaps

Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

Understanding surface discharge activity with epoxy silicon carbide nanocomposites

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