Study on the properties of enhanced plasma injection driven by electrical explosion of aluminum wire in PTFE capillary in high-pressure SF6

Abstract

Enhanced plasma injection (EPI) driven by the electrical explosion of a metal wire in a microcavity has been proven to be an effective method for triggering 10-cm-magnitude high-pressure SF6 gas gap at very low working coefficients and provides a potential technical routine for ultrafast bypass switches (UFBPSs). In this study, aiming to further promote the EPI strength and improve its triggering ability, the EPI actuator is optimized, and several vital parameters of the actuator structure, including diameter D and length L of the microcavity and nozzle shape, are investigated. EPI with a maximum height of ∼10 cm and an initial velocity of ∼1000 m/s can be realized in 0.5 MPa SF6 when a 600 μm aluminum wire is exploded by a ∼1000 J trigger pulse. The EPI strength vs D curve has an inverted V shape, and 2 mm D results in the most intense EPI, due to the competitive effect of the vent congestion inside a thin capillary and parasitic volume in a fat capillary. As L increases, the EPI strength increases to saturation and then decreases. A 20–23 mm L can yield suitable EPI strength with limited trigger energy. The nozzle shape has a remarkable influence, and a divergent-type nozzle leads to a much stronger EPI than the shrink-type or straight-type nozzle, generating an EPI with a maximum height of 12 cm and an initial velocity of 1600 m/s. This study provides a useful guidance for the EPI actuator design for triggering megavolt UFBPSs at very low working coefficients.