Development of a practical continuous on-line partial discharge monitor for generators and motors

An automatic partial discharge monitoring system has been developed to continuously measure the PD activity in operating motor and generator stator windings. The system is intended for long term use by electric utility and industrial plant personnel, rather than researchers. The system is resistant to false indications of high PD activity caused by noise, since noise is eliminated on a pulse-by-pulse basis, using specialized sensors permanently installed on the stator winding. The control software enables recording of PD data under machine operating conditions and at a frequency that the user specifies, thus reducing the amount of data stored to realistic quantifies. In the past year, the system has been installed on 19 generators, in 4 plants and 2 utilities. The operating principles of the system are described, and some preliminary results are presented.