Abstract
Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make 252 kV GIS basin insulators. Some voids with different diameters or cracks with different diameters and orientations were artificially made in the specimens with different thicknesses. An ultrasonic pulse-echo system was set up, and ultrasonic tests were carried out on the specimens with voids or cracks. A method to calculate the depth of a defect was proposed by the propagation time of defect reflected waves. The results showed that a depth of 50 mm, a diameter φ of 2 mm void, and a diameter φ of 1 mm crack in epoxy composite insulation were detected by the ultrasonic system using a 1 MHz transducer.
Highlights
Because of its advantages such as high reliability, small ground space requirements, long maintenance cycle, and low environmental impact, the gas-insulated metal-enclosed switchgear (GIS)is widely used in large-scale hydropower projects and urban high-voltage power grids with a complex terrain and a narrow area
Conclusions voids with diameters of 1 mm and 2 mm, and the characteristics of partial discharge patterns are
From the PD measurement, it is difficult to distinguish voids with diameters of 1mm and orientations were artificially made in epoxy composite specimens similar to 252 kV GIS basin
Summary
Because of its advantages such as high reliability, small ground space requirements, long maintenance cycle, and low environmental impact, the gas-insulated metal-enclosed switchgear (GIS). In 2000, Mouritz et al [23] used the ultrasonic pulse-echo method with a low frequency, based on gain change, to detect the delamination and cracks caused by fatigue damage in glass fiber-reinforced laminated composites between 7 and 38 mm thick. In 2015, Shen et al [32,33] detected internal air gaps and cracks in epoxy composites with a thickness of 30 mm by ultrasonic waves This method was able to distinguish air gaps between 2 and 1 mm in diameter and cracks with different orientations by analyzing the spectrum of bottom reflected waves. The low frequency, ultrasonic pulse-echo method [34] was used to detect bubbles 5 mm in depth and 2 mm in diameter in the insulation pull rod, with a cylindrical structure, of a circuit breaker. An ultrasonic pulse-echo method was proposed to detect internal defects in an epoxy composite specimen similar to basin insulators. Reflected waveforms at voids with different diameters and cracks with different orientations were
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