Acoustic diagnoses of GIS; field experience and development of expert system

The authors report on the practical aspects of acoustic diagnoses of gas insulated substations (GIS). Thirty-eight tests have been carried out during factory testing, commissioning testing, and service. The number of flaws revealed in the tests varies considerably. The flaw frequency in a GIS probably reflects the care taken during assembly. The results from the field tests reported verify that the acoustic emission method is suited for identifying and locating flaws in GIS. Using low-frequency (20-80 kHz) sensors, the method is sensitive to the most important flaws in the insulation system. The test procedures as well as criteria for source recognition, localization, and evaluation are discussed. An expert system assisting operators in diagnosing flaws in GIS is described. The system creates a database containing a representation of the GIS and the observations and conclusions from the acoustic test