Moisture is detrimental to the performance of epoxy resin material for electrical equipment in long-term operation and insulation. Therefore, moisture absorption is one of the critical indicators for insulation of the material. However, some relevant test methods, e.g., the direct weighing method, are time-consuming, and it usually takes months to complete a test. For this, it is necessary to have some modification to save the test time. Firstly, the study analyzes the present prediction method (according to ISO 62:2008). Under the same accuracy, the time required is reduced from 104 days to 71 days. Subsequently, the Langmuir curve-fitting method for water absorption of epoxy resin is analyzed, and the initial values of diffusion coefficient, bonding coefficient, and de-bonding coefficient are determined based on the results of molecular simulation, relevant experiment, and literature review. With the optimized prediction model, it takes only 1.5 days (reduced by 98% as compared with the standard prediction method) to determine the moisture absorbability. Then, the factors influencing the prediction accuracy are discussed. The results have shown that the fluctuation of balance at the initial stage will affect the test precision significantly. Accordingly, this study proposes a quantitative characterization method for initial trace moisture based on the terahertz method, by which the trace moisture in epoxy resin is represented precisely through the established terahertz time-domain spectroscopy system. When this method is used to predict the moisture absorbability, the experimental time may be further shortened by 33% to 1 day. For the whole water absorption cycle curve, the error is less than 5%.

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The united frameworks of UHV and EHV substation belong to wind-sensitive structures, and wind load is one of the main control loads of the design. In this paper, a 500kV full united substation framework was used as the engineering background to explore the quantitative relationship between wind-induced vibration coefficient, damping coefficient and average wind speed of the full united framework. The results showed that the average wind speed and the damping coefficient of the framework have significant influence on the wind vibration coefficient of the framework. The research results in this paper not only provide theoretical and computational basis for the wind resistant design of the combined framework structures, but also provide a basis for formulating the design criteria of full united wind vibration coefficient.

As an important part of composite insulator, glass fiber reinforced polymer (GRP) rod needs to bear the main mechanical and keep certain insulation performance. The void in the material is key factor to the performance of GRP rod. The void with larger size could affect the electric field distribution significantly and lead to the “Lantern-like” heating. In this paper, the structure of void in GRP rod is studied by 3D X-ray microscope. It is found that the void dimensions in the GRP rod is generally less than 300μm, but the interconnection of linear hole makes the length of the void increase significantly. For the GRP rod with high porosity, the length of connection hole is hard to be detected directly by the existing technology, but it could be calculated based on the diameter of the hole. Based on the calculation method, the dimensions of void in GRP rod could be inspected by the observation of section using optical microscope.

The full united frameworks (FUF) of transformer substations belong to wind-sensitive towering structures, and wind load is a decisive control load. Wires, lower leads, and busbars hang on united frameworks. Such suspension component will inevitably affect the wind-induced response characteristics of united frameworks, which must be considered in design. In this study, a 500kV full united substation framework was used as the study object. Six busbars was installed in longitudinal direction on the framework. With the help of finite element analysis software ANSYS, based on random vibration theory, the wind-induced vibration response of the united framework was calculated and analyzed in frequency domain. The wind induced vibration displacement response and the spatial distribution rule of the wind vibration coefficient under the wind load in different wind directions were obtained. The calculation results show that, with the existence of longitudinal busbars, the fluctuation displacement response and the wind vibration coefficient of the transformer framework decreased, which reduced the alternating load of the transformer framework, with the location of the maximum displacement of the fluctuating displacement response transferred to the busbars. The existence of the busbars has little effect on the mean displacement response of the transformer framework, which can be ignored in the design phase of the transformer framework.