Combined light and voltage stimulus triggers localized cation migration, nonlinear lattice deformation, and nanoscale structural rearrangement in perovskite films providing insight into perovskite optoelectronic device instability.

The internal defects in composite insulators, for example void, delamination, and interface debonding, can lead to partial discharge, flashover, and even result in cracking and breakdown, threatening the safe operation of power system. In this study, various defects were artificially made in the 10 kV composite insulators. The ultrasonic phased array method was employed to detect these defects, by using a concave probe designed to ensure complete coupling between the probe detection surface and the curved insulator surface. The results show that these artificial defects can be detected through the detection ultrasonic images. Moreover, compared to previous studies, a smaller through-hole (0.3 mm diameter) in the housing and a smaller through-hole (0.5 mm diameter) in the core can be successfully detected. Additionally, the depths of defects can be determined from the detection images, and the deviations in depth for the defects were less than 9.3%. Moreover, the resolution for detecting the through-holes in the housing is enhanced.

The mechanical reliability of the gas-insulated metal-enclosed switchgear (GIS) is critical to the safe and stable operation of a power system. The internal stress induced in GIS insulators, which typically lead to cracking, can degrade the mechanical properties and compromise the reliability of the GIS. In this work, ultrasonic nondestructive measurements of the internal stress in a GIS 126 kV epoxy composite with the transverse waves are demonstrated for the first time. Our results show that the velocities of ultrasonic transverse waves increase linearly with the compressive stress and decrease linearly with the tensile stress. The acoustoelastic coefficients are −1.18 × 10⁻⁴/MPa and −1.96 × 10⁻⁴/MPa for measurements with transverse waves polarized vertically and parallelly to stress, respectively. Based on these acoustoelastic coefficients, the internal stresses are calculated, and the maximum absolute values of relative errors are 35.4% and 26.3% for measurements with the transverse wave polarized vertically and parallelly to stress, respectively.