Room temperature vulcanized (RTV) silicone rubber is extensively used in power system due to its hydrophobicity and hydrophobicity transfer ability. Temperature has been proven to markedly affect the performance of silicone rubbers. This research investigated the degradation of RTV silicone rubber under temperature cycling treatment. Hydrophobicity and its transfer ability, hardness, functional groups, microscopic appearance, and thermal stability were analyzed using the static contact angle method, a Shore A durometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG), respectively. Some significant conclusions were drawn. After the temperature was cycled between −25 °C and 70 °C, the hydrophobicity changed modestly, but its transfer ability changed remarkably, which may result from the competition between the formation of more channels for the transfer of low molecular weight (LMW) silicone fluid and the reduction of LMW silicone fluid in the bulk. A hardness analysis and FTIR analysis demonstrated that further cross-linking reactions occurred during the treatment. SEM images showed the changes in roughness of the RTV silicone rubber surfaces. TG analysis also demonstrated the degradation of RTV silicone rubber by presenting evidence that the content of organic materials decreased during the temperature cycling treatment.

The outdoor ultra-high voltage (UHV) dry-type air-core smoothing reactors (DASR) of High Voltage Direct Current systems are equipped with a rain cover and an acoustic enclosure. To study the convective heat transfer between the DASR and the surrounding air, this paper presents a coupled model of the temperature and fluid field based on the structural features and cooling manner. The resistive losses of encapsulations calculated by finite element method (FEM) were used as heat sources in the thermal analysis. The steady fluid and thermal field of the 3-D reactor model were solved by the finite volume method (FVM), and the temperature distribution characteristics of the reactor were obtained. Subsequently, the axial and radial temperature distributions of encapsulation were investigated separately. Finally, an optical fiber temperature measurement scheme was used for an UHV DASR under natural convection conditions. Comparative analysis showed that the simulation results are in good agreement with the experimental data, which verifies the rationality and accuracy of the numerical calculation. These results can serve as a reference for the optimal design and maintenance of UHV DASRs.

In China, the average elevation of Yunnan Province exceeds 2000 m, with a greatly fluctuating terrain. Most areas have a high-altitude mountainous terrain and relatively high ground lightning activity. Topography is one of the most critical factors affecting regional lightning characteristics. Therefore, clarifying the quantitative relationship between cloud-to-ground lightning activity and topography can help evaluate the risk of hazard-pregnant environments and adopt active protective measures. In this study, we used a mathematical statistical method to analyze the correlation between cloud-to-ground lightning density and altitude, slope, slope aspect, topographic position index, and land-cover type in Yunnan for the past 10 years. We also used the Apriori algorithm to study the coupling effects of different topographic factors and mine the topographic attribute sets that strongly correlate with high-level lightning activity. We used the entropy weight method to construct a comprehensive index of hazard-pregnant environments and quantitatively evaluate the impact weights of different factors on cloud-to-ground lightning activity. Correlation analysis of lightning density and sensitivity indicated a correlation coefficient of 0.473 between both factors, highlighting the effectiveness of evaluating regional lightning risk with the sensitivity of a hazard-pregnant environment

Compared with other lightning targets on the ground, the most notable feature of a wind turbine is that the blades are usually in a rotating state when lightning strikes. To study the mechanism of blade rotation influencing wind turbine on triggering lightning, lightning discharge comparison tests based on a typical 2-MW 1:30-scaled wind turbine model with an arching high-voltage electrode were conducted under different modes of stationary and rotating blades. Negative polarity switching impulses of 250/2500 μs were applied to the arching electrode. The up-and-down method was adopted for 50% discharge voltage and the discharge process was observed. The experimental results showed that under the condition of a 4 m gap, the breakdown voltage decreases and the connection point of the leaders approaches the high-voltage electrode with increasing blade speed, indicating that the wind turbine’s blade rotation enhances the triggering of lightning. The analysis showed that the blade rotation could be altering the charge distribution on the blade tip, resulting in varied ascending leader development on the blade tip, which affected the discharge development process.