Method of monitoring the quality of filler gases, in particular

Details Method of monitoring the quality of filler gases, in particular Method of monitoring the quality of filler gases, in particular

1998-04-30

2000-01-04

Westin, Edward P.

Radiant energy

Ionic separation or analysis

Ion beam pulsing means with detector synchronizing means

250288, 250282, B01D 5944, H01J 4940

Patent

active

060112581

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a method of monitoring quality of filler gases, in particular of a sulfur hexafluoride (SF.sub.6), in a gas-filled installation, in particular in gas-insulated switch units, such as high and medium voltage switches.
In gas-insulated high and medium voltage installations or containers, the filler gases are put in as insulation gases. At that, preferably sulfur hexafluoride (SF.sub.6) is used because SF.sub.6 combines a number of important characteristics which favors its use such as high insulation property, distinguished arc quenching characteristics, non-toxicity, high thermal and chemical stability, a small dielectric loss factor, high gas density, and favorable heat transfer characteristics. Though SF.sub.6 has, under normal conditions, a constant chemical bonding, high thermal loads and electrical discharges destroy the SF.sub.6 molecules. Gas-insulated switch units, therefore, provide for a qualitative retaining of insulation. However, during an operation, one cannot insure that this gas would not decompose if suitable counter-measures are not taken. This decomposition can be caused, e.g., by overheating at a connection location. Partial discharges on defected screen electrodes or direct gas breakdowns should be avoided. The decomposition products produced in this way are partially very high toxic and very corrosive. In addition, they adversely affect the electrical strength of the SF.sub.6 insulating gas in switch apparatuses and installations which, together with increasing dissipation of the installation-filling gas determines the operational reliability of distribution of electrical energy.
These exemplary and known negative effects on the insulating property of the SF.sub.6 gas require that very high standards be observed during the manufacture of the SF.sub.6 installations and a constant monitoring of the insulating gas. It is known that despite high manufacturing quality and the undertaken measures such as fitting in of molecular sieves or absorption fitters in the installation in order to tie up water or gaseous decomposition products, long-life characteristics of the installation can deteriorate. Thus, e.g., partial discharges in gas-insulated switches can be measured directly. Because the formation of gaseous decomposition products worsens the electrical strength of a SF.sub.6 installation, the quantative data about the electrical strength of SF.sub.6 gas with decomposition products is of a big interest for power suppliers as operators of such an installation. The same is true for numerical values of reduction of the withstand voltage of the pin insulators under the influence of the humidity and the decomposition products. These data are indispensable for a gas diagnostics, e.g., for determining the time point of a gas exchange or of an event controlled revision as a long-range objective. A further planned use of the gas diagnostics is determining the fault location and the type of the fault. The fault location is found based on concentration differences in separate selected regions of the installation. The type of the fault can be determined from separate components of the decomposition products. Quantitative data related to the electrical strength of SF.sub.6 gas including impurities of its decomposition products are obtained from experiments with a direct current corona discharge in a scientific apparatuses and off-line sampling and analysis in electrical switch units. To this end, test tubes for the web chemical method and the Fourier-transform-infrared spectroscopy as well as mass spectrometry are used. Conclusions based on acoustic methods with regard to the quality of the isolation gas are labor-consuming and instrumentation-consuming, are not completely precise and, at that, are relatively expensive. All of the above-mentioned methods are gas analytic laboratory methods, which are highly delicate and have a good selectivity, are off-line methods and, therefore, can indicate the operational condition of an installation only with a time delay. In additi

REFERENCES:
patent: 3211996 (1965-10-01), Fox et al.
patent: 4633082 (1986-12-01), Sauers

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