A new technique for the detection of defects in HV groundwall insulation of generator stator windings

Some defects such as voids and cracks often exist in groundwall insulation due to problems associated with technology. This is a big hidden trouble to the generator, and may lead to the breakdown of insulation in the stator windings finally. In this paper a multi-function instrument with digital signal processing system is developed for detecting the defects within groundwall insulation in generator stator windings. When the stator windings are tapped with a vibrator, a sound containing the information of defects is produced, and picked up by using an acoustic transducer, followed by sound signal analysis. The detected results are displayed on a liquid crystal display and printed by a microprinter. Comparing with the conventional detecting methods, the new technique has advantages such as higher resolution, real time display of results and convenience for operation