At present, observing the temperature rise of composite insulators is an effective method for the detection of decay‐like defects. However, ambient humidity will affect the temperature rise of composite insulators, which will cause problems in screening the decay‐like composite insulators. Therefore, it is urgent to study the temperature rise principle of decay‐like insulators and find out the influence mechanism of humidity on temperature rise. In this study, a four‐electrode system is designed to measure the surface current, volume current and interface current of the decay‐like short sample and the intact short sample under different humidity. Then the equivalent circuit models of short samples and the 500 kV full‐size decay‐like composite insulator are built to analyse the contribution rates of leakage conductance loss and polarisation loss to temperature rise. The results show that the contribution rates of the polarisation loss to the temperature rise of two samples are 35.8% and 23.6% in low humidity, while they are 98.3% and 64.4% in high humidity. For the full‐size decay‐like composite insulator, the contribution rates of polarisation loss to its temperature rise in high or low humidity are more than 99%. In addition, the proportion of polarisation loss increases at first and then decreases with the increase of the length of the decay‐like section. The conclusions of this study provide a theoretical basis for further understanding the corresponding relationship between decay‐like defects and temperature rise and improve the detection rate of decay‐like insulators.

Abnormal heating of composite insulators on ultra‐high voltage (UHV) transmission lines is widespread under high humidity and heat in southern China. The infrared imaging technology can be used of quickly and effectively detect insulators with abnormal heating and determine their defect types. However, it may cause misjudgement when the infrared images are not clear. A super‐resolution reconstruction method of infrared images of composite insulators with abnormal heating based on improved super‐resolution generative adversarial networks (SRGAN) is proposed in this paper, and the dense residual network in SRGAN is perfected by introducing the residual channel attention (ResCA). This method overcomes the problems that the resolution of images reconstructed by traditional methods is not significantly improved, and images are too smooth, and the edge details are easily lost. Compared with the traditional methods, the five reference‐free image quality evaluation indexes of the image reconstructed by the improved SRGAN are increased by −0.73% to 63.84%. Further the effectiveness and superiority of the improved SRGAN are verified by comparing the changes in the distribution of grey values of infrared images before and after reconstruction. Finally, the improved SRGAN is used to perform super‐resolution reconstruction of the low‐resolution infrared image examples.

At present, the temperature rise in insulators is observed using infrared thermometry as a common method of diagnosing decay-like insulators. However, the original characteristic data obtained by infrared thermometry cannot effectively distinguish some of the decay-like insulators from those with ageing sheaths. Therefore, it is imperative to find a new diagnostic characteristic quantity. Based on statistical data, this article first explains that existing diagnostic methods have limited diagnostic effectiveness and a high false detection rate for insulators in a slightly heated state. A full-scale temperature rise test is carried out on a batch of composite insulators returned from the field under high-humidity conditions. Two different defective insulators with similar temperature rise profiles are identified, and an electro-thermal coupling simulation model is developed based on the dielectric characteristic parameters of the above insulators for both core rod defects and sheath ageing. A new infrared diagnostic feature, the temperature rise gradient coefficient, is then obtained to identify the source of abnormal heat in insulators using statistical analysis of an infrared image gallery of abnormally hot composite insulators obtained from field inspections and laboratory tests.

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Topological phononics are well known for their topological edge states due to the backscattering immunity and pseudospin dependent phonon transportation. Here, we study two types of topological edge states on valley phononic crystal plate. We magnify the transversely symmetric and antisymmetric property by observing the displacement distribution in both simulation and experiment. We underline the theoretical origin of transversely symmetric and antisymmetric property based on a simplified mass-spring model, i.e., the combination of the phase difference caused by the periodicity of PC plate and the phase difference between sites p and q in unit cell. Our results enrich the features of topological edge states, and offer the possibility for designing mechanical device or controlling the wave propagation along phonon circuits.