Ultrasonic inspection of gas-insulated high-voltage substation(GIS) spacers has been conducted and, based on the limited evaluation todate, it appears to provide a viable means of detecting defects. Usingcommercially available ultrasonic equipment coupled to a motor drive andsoftware data collection system, this method has been successful inlocating voids, agglomerates of contaminating particles, and epoxy-metalinterface debonding in GIS spacers that failed to pass factoryqualification tests. Manual probe application has also proven capable oflocating defects. A series of defects including voids, metalcontaminants, and paper fragments could be detected in a set of testspecimens. A spatial resolution of approximately 1 mm has been attained.The correlation between ultrasonic results and forensic examination hasbeen very good. The spacers used in this evaluation had previously beensubjected to nondestructive X-ray tomographic inspection, which failedto disclose any internal defects. Scattering of the ultrasonic signal bythe inorganic fillers has resulted in enlargement of the apparentdimensions of features. The fillers have not hindered detection offeatures within epoxy sections approximately 180 mm thick
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