Abstract
A model circuit breaker in a high-pressure chamber filled with CO2 atmosphere is used to operate a wall-stabilized arc of several kilo-amperes between tungsten-copper electrodes surrounded by polytetrafluoroethylene nozzles. Optical emission spectroscopy (OES) is carried out via quartz plates inserted into the nozzles using a combination of an imaging spectrometer either with a high-speed video camera or with an ICCD camera. Depending on the nozzle geometry and the current, continuum from C2 Swan bands was detected as absorption as well as emission pattern. After current zero, optical absorption spectroscopy (OAS) using a xenon flashlamp as broadband background radiator was applied. An absorption around 493 nm was detected and attributed to CuF molecules. The study proofs the existence of C2 in the active phase and the formation of CuF near to current zero.
Highlights
Self-blast circuit breakers are based on the ablation of material from a nozzle producing a pressure build-up in a heating volume that is used for arc quenching around current zero (CZ)
A model circuit breaker in a high-pressure chamber filled with CO2 atmosphere is used to operate a wall-stabilized arc of several kilo-amperes between tungsten-copper electrodes surrounded by polytetrafluoroethylene nozzles
Optical emission spectroscopy (OES) is carried out via quartz plates inserted into the nozzles using a combination of an imaging spectrometer either with a high-speed video camera or with an ICCD camera
Summary
Self-blast circuit breakers are based on the ablation of material from a nozzle producing a pressure build-up in a heating volume that is used for arc quenching around current zero (CZ). The CZ crossing and the period immediately after current interruption are of high importance for the interruption performance. In these time intervals several physical effects occur, such as flow reversal in the heating channel, transition from an ablation-controlled to an axially blown arc, the extinction of the arc and a continued evaporation of nozzle material after current zero due to the preceding thermal stress. The determination of dielectric properties, i.e. the plasma composition, pressure and temperature, as close as possible to current zero is mandatory for an improvement of interruption capability. Determination of plasma temperature profiles was limited to 0.4 ms before CZ
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