EXPERIMENTAL STUDIES OF THE PHYSICAL AND MECHANICAL PROPERTIES OF CAST-RESIN INSULATION MATERIAL OF BUSBAR SYSTEM

Experimental studies of the physical and mechanical properties of «factory» and «field» types of cast-resin insulation material are carried out in the framework of scientific research regarding the reliability and safety assurance of cast-resin insulated busbar systems. Insulation of the «factory» type (FT) is used in manufacture of sections of the busbar system, whereas insulation of the «mounting» type (MT) is used to isolate the joints of sections during their installation. Analysis of the operational factors revealed a set of the physical and mechanical properties of cast-resin insulation material which affects most strongly the strength of the busbar system. The studies included determination of the elastic characteristics and ultimate strength by the method of static mechanical tests of flat specimens for tension and three point bending. The tests were performed at low, zero and high temperatures according to operation modes of the busbar system. The coefficients of linear thermal expansion of the material for two temperature ranges were determined using rod specimens. The density of the material was measured by measuring size and weight of the specimens. All experiments were carried out using the methods listed in state standards. The results of the experiments showed a distinct effect of temperature on the Young’s modulus and the ultimate strength of the insulation material in bending tests. The ultimate strength of the MT insulation is 7 – 30% higher compared to FT insulation due to the fine and more uniform structure of MT insulation. As a whole, the mechanical properties determined in the experiments are significantly lower than the mechanical properties declared by the manufacturer. This can lead to reassessment of the strength of cast-resin insulation during safety control of busbar systems considering the declared values of the mechanical properties. In this regard, the obtained results should to be taken into account in calculation of the stress-strain state of the busbar systems with cast-resin insulation at different operation temperatures.

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