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Gas-Insulated Self-Breakdown Spark Gaps: Aspects on Low-Scattering and Long-Lifetime Switching

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Frey W., Sack M., Wuestner R., Mueller G.

Acta Physica Polonica A

2009

vol. 115

issue 6

1016-1018

The influence of the electric field distribution between the electrodes and the seed electron generation rate on the scattering of the breakdown voltage of SF_{6}-insulated spark gaps was investigated. The breakdown voltage scattering considerably can be reduced by applying large-gap-volume, uniform-field electrode profiles instead of spherical shaped electrodes. Moreover, uniform field electrode profiles exhibit an uniform discharge probability in the entire gap volume and following an almost uniform erosion of electrode material along the electrode's surface. This preserves electrode shape and switching performance of the spark gap for a long maintenance-free lifetime. Breakdown voltage scattering further can be reduced by increasing the seed electron generation in the gap by an auxiliary corona discharge adjacent to the main gap. The experimental observations are discussed on the basis of the volume time law for discharge initiation.

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Sack M., Attmann F., Stängle R., Wolf A., Frey W., Müller G.

Acta Physica Polonica A

2009

vol. 115

issue 6

1081-1083

For the production of synthetic bio-fuel the use of green biomass enables additional resources of raw material supplementary to the commonly used dry material. An electroporation assisted drying process gives the opportunity of a more efficient dewatering than only pressing and subsequent drying. Experiments showed a lower relative humidity of the pressed material after electroporation compared to pressing the raw material only. Moreover, the drying process of the electroporated material was much shorter. This is because the pores formed in the cell membranes foster a better extraction of water during pressing and enhance the diffusion process during the drying process. The paper presents exemplarily the experimental results for green rye. For the electroporation-assisted drying process the electric contact to the plant material has to be established by means of the juice inside the plants only rather than adding additional water. Hence, for experiments in larger scale, the existing electroporation device KEA-MOBIL has been equipped with a new combined electroporation reactor and press. The reactor has a plate electrode system, whose upper electrode additionally serves as a piston to apply mechanical force to extract juice for a good electrical contact between plant material and the electrodes. A two-stage Marx generator serves as a pulse source. To reduce the insulation distance to the walls of the shielding cabin the Marx generator is operated in ground symmetric configuration. The device has been designed for a batch-wise throughput of 50 kg/h. An automatic feeding device enables the alternating use of two test vessels. The device has been tested on-site on a farm with green rye and grass.

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2 Acta Physica Polonica A

2 2009

2 Frey W.

2 Sack M.

1 Attmann F.

1 Mueller G.

1 Müller G.

1 Stängle R.

1 Wolf A.

1 Wuestner R.

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Gas-Insulated Self-Breakdown Spark Gaps: Aspects on Low-Scattering and Long-Lifetime Switching

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