Features of Applying Cast Epoxy Insulation and Compositions Based on It for High-voltage Equipment

The article considers the features of applying cast epoxy insulation (LEI) and compositions based on it in high-voltage equipment. The LEI structural characteristics are studied, including its microheterogeneous structure and the effect of globules on electrical strength. Operational factors, such as the insulation volume and structure, voltage exposure time, and operating temperature, are discussed. The advantages of cycloaliphatic epoxy resins in comparison with conventional resins based on bisphenol A and F, as well as the effect of various fillers on the insulation mechanical and electrical properties are considered. Examples of LEI application in transformers, switchgear and busbars are given along with methods for increasing the insulation electrical strength by optimizing the composition of compounds and the insulation system structures. The absolute value of local electric field intensities in the dielectric is discussed, which depends both on the average electric field intensity in the vicinity of field inhomogeneities and on the parameters of the inhomogeneities themselves. The results of experimental studies and statistical analysis of the dependence of electrical strength on the cast epoxy insulation thickness are considered, which demonstrate that in a quasi-homogeneous electric field, a decrease in the insulation electrical strength with an increase in the interelectrode distance is due to a change in the dielectric "active volume".