High PD Activity in Unit 3 Noxon Rapids Became Low After Rewinding

Published Nov 15th, 2006


Avista Utilities

Machine Description:

Hydraulic Generator, 108 MW, 13.8 kV

Installed in 1959 and rewound in 1975, 1983 and 2004
Two Bus Couplers per phase

High Partial Discharge Activity in Unit 3 Noxon Rapids Became Low After Rewinding

In 1998, partial discharge measuring equipment was installed as part of the control/monitoring systems upgrade. This consisted of two capacitive couplers on each phase connected to a HydroTrac continuous on-line monitoring system. When commissiong the system, engineers from Iris remarked that Unit 3 had some of highest partial discharge activity they had ever seen. Avista used data supplied by the partial discharge equipment to track stator winding condition. Partial discharge remained at very high levels and steady until the unit was rewound in 2004. Partial discharge activity has returned to levels expected from a new winding. It will be monitored over the life of the winding for signs of insulation decay.






Excerpt from article “Using On-Line Monitors to Improve Performance and Plan Corrective Actions”, by M. Walden and J. Hamill” in Hydro Review / November 2005



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