Bushing Failures with Rapid and Very Rapid Evolution Time Detected by Online Monitoring

摘要

Because many transformer failures originate at the bushings, and in order to reduce the shutdowns for testing, the offline tests on bushings have been replaced by online monitoring, which has been providing new data on the time of evolution and the way the defects evolve. In general, it was believed that the failures in bushings evolve slowly, in weeks or months. While this is true in many cases, this paper presents the experiences by Brazilian electric power utilities Chesf and Eletrosul, in which online monitoring data indicated defect evolution times of minutes or hours. A new methodology for detection and alarming of rapid evolution defects will be introduced which, when used with the current slow evolution failure detection techniques, will result in an increased reliability of the electric power supply.