Electrode erosion characteristics of repetitive gas spark switch under airtight and large current conditions

Summary form only given. With rapid development of pulse power technology, gas spark switch has broadened its application in industrial fields, such as the extraction of unconventional gas resources. Combining repetitive gas spark switch technology with underwater electrical wire explosion technology can provide a new technology for unconventional shale gas development. Therefore, based on requirements of practical engineering applications, the repetitive gas spark switch needs high current capability, low breakdown voltage dispersancy, and long lifetime in an airtight cavity without gas blowing system. The purpose of this paper was to study the electrode erosion characteristics under adverse conditions and to analyze the failure of the switch. The relationships between circuit parameters, environment conditions and electrode erosion characteristics are worth to be investigated. A test stand was established to investigate the Cu-W (90 wt%) two-electrode spark-gap switch working in an airtight cavity (1.18 L) without gas blowing system. The equipment was divided into five parts, a DC power, a pulse capacitor, a Cu-W two-electrode gas spark switch, a low inductance load resistor and measurement systems. Besides, the structure was compact for there was no cable among five parts. The switch was tested with frequency of 0.1 Hz, self-breakdown voltage of 30 kV, peak current of 50 kA. A Rogowski coil with the sensitivity of 0.0005 V/A and a capacitance-resistance divider with attenuation ratio of 4730 V/V have been designed for the measurements of transient large current and high voltage respectively. A scanning electron microscope is used to observe the surface of the electrodes. A Bruker Tensor 27 FTIR Spectrometer and an X-ray photoelectron spectroscopy are used to analyze the chemical composition of erosion product. The surface roughness of electrodes could be assessed by a dynamic 3D aspheric profile.