Use of dielectric tests as an aid for hydro generator maintenance

A broad overview of tests performed as part of hydroelectric generator monitoring/maintenance at Electricite de France is provided. Special attention is devoted to dielectric testing of stator winding insulation. More than 30 years experience at the Hydropower Generation Division resulted in the adoption of a procedure for maintenance by periodic testing. These tests, organized according to three levels of periodicity and contents which can be adapted, allow detection and monitoring of mechanical, electrical, thermal, and dielectric damage. On the basis of this information, especially the dielectric tests, objectives in terms of production facility lifetime and availability, as well as optimization of maintenance costs, have been achieved successfully on over 1200 machines in service by implementing maintenance adapted to the equipment