The early phase of dielectric surface flashover in a simulated LowEarth Orbit environment

摘要

In Low Earth Orbit (LEO) the environment space plasma and UVradiation influences the surface charging and the surface flashovervoltage of insulators, and thus the performance of high voltage systems.Understanding the mechanisms leading to surface flashover will make itpossible to apply certain shielding techniques (e.g. electric andmagnetic shielding) which can increase the dielectric flashover voltagedrastically. In our experimental apparatus, a dc voltage up to 50 kV ora voltage pulse (up to 100 kV with 200 ns duration) is applied to thetest gap. The geometry of all interconnecting lines and of the dischargechamber is coaxial and the impedances are closely matched. Breakdowncurrent and voltage are recorded by highly sensitive sensors withrisetimes of less than 0.8 ns. Preliminary results with a plasmabackground have shown a change from a surface dominated flashover to aplasma dominated breakdown compared to measurements in vacuum with zeroplasma density. With applied UV radiation the dielectric flashovervoltage amplitude decreases and the voltage and current waveform isaltered, compared to results without UV, indicating a different currentamplification mechanism in the early phase of dielectric surfacebreakdown