The Primary Aspects of Improving the Electrical Strength of Cast Epoxy Insulation on High-Voltage Devices

Abstract

Various technical solutions are used to meet existing requirements for insulating high-voltage equipment, and the widespread introduction of solid insulation is one of them. Recently, there has been a noticeable wide transition to composite materials with improved strength properties. To justify the use of such materials, it is necessary to be guided by statistical laws of electrical strength distribution from various parameters, particularly the size of insulation, and its volume, to analyze breakdown probabilities. When selecting an appropriate type of material, one should also rely on the filler's type, size, and structure, temperature coefficient difference of linear expansion for electrode and cast insulation materials, and a possible increase in adhesion of metal elements epoxy compounds. The article considers in detail the issues of determining the distribution of electrical strength from various parameters, describes the theories of dielectric failure and ways to increase insulation, and also presents for the first time the experience of high-quality adhesion of electrodes with composite materials in the absence and pre-application of a small layer of compound on the electrode surface before the main filling with solid insulation. The presented results cover experiments on the strength of cast epoxy insulation samples when activating the electrode surface with alkali, potassium dichromate, and in the absence of activation. At the same time, for a better understanding of the ongoing processes and changes in the electric field strength, the main influencing factors and the mechanisms of the electrical breakdown development are taken into account.