Abnormal heating due to decay-like degradation in composite insulators is influenced by environmental moisture

but the relationship between the internal degradation status of the core rods and their electrical properties under varying humidity conditions remains poorly understood. In this work

the decay-like degraded fibre-reinforced polymer (FRP) core rod was dissected into short samples for light transmission analysis

and their moisture absorption performances were tested. Electrical parameters under both DC and AC voltages were measured under different hygroscopic conditions. It was observed that the dielectric loss of severely degraded samples increased dramatically after moisture absorption

and a remarkable correlation between degradation area and electrical parameters was found. Based upon the axial variation of electrical properties along the rod

the branched-structure theory was proposed to interpret the sharp changes in electrical properties within the transitional region. Furthermore

Fourier transform infrared spectroscopy (FTIR)

micro computed tomography (micro-CT) and scanning electron microscope (SEM) were employed to investigate the changes in chemical composition and microstructures responsible for the enhanced moisture absorption capabilities within severely degraded regions. This study explored the influence of moisture on the degraded core rod and its impacts on electrical properties

which laid the foundation for future research into the abnormal heating mechanism.