LAUSR

Gas discharge tube (GDT) breaks down discharge with surge overvoltage during long-term use. Notably, there is a risk of short-circuit failure due to the drop in insulation resistance after a certain number of discharges, which might be mainly caused by cumulative discharge. This article builds a cumulative discharge experiment platform to analyze the failure mechanism, performed the GDT whole life cycle cumulative discharge experiment and focused on the change law of its insulation resistance and breakdown voltage. For samples that are short-circuited, X-ray observation and vibration testing perpendicular to the GDT axis are conducted to examine the internal micro-morphology without damaging their external structure. The GDT is opened and its internal structure and material properties of the GDT cavity are compared and analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) methods. The results indicated that the insulation resistance of GDT continuously decreased by several orders of magnitude in the last 10% of the life cycle, and the insulation resistance before failure is generally less than 1 $\text{k}\Omega $ . Through X-ray observation of the short-circuit failure sample, two different abnormal growth phenomena in the cavity are found, including flocs between the electrodes and deposits on the tube wall. Further analysis and experiments demonstrated that the flocs between the electrodes and the deposits on the tube wall are the primary factors causing the degradation of GDT insulation performance. The formation mechanism of the two short-circuit modes is explained by the difference in the splash angle and mode of metal particles of different sizes on the electrode surface.