The importance of phase resolved partial discharge pattern recognition for on-line generator monitoring

Remote monitoring of the partial discharge activity on a 820 MVA turbine generator was carried out over several months. At least 8 characteristic signatures were recorded, some of which were always present, others occurring only sporadically. The nature of the activity causing most of those signatures could be identified when compared to laboratory simulations. Some cross-coupling did occurred between phase windings. Results clearly showed that recognition of phase resolved patterns by an expert is still necessary to sort out cross-coupling between phase windings, and to discriminate one source of discharge from another