HYDRO GENERATORS WITH WATER-COOLED TYPE STATOR WINDING: DIFFICULTIES AND SOLUTIONS ON DOING DIELECTRIC TESTS

摘要

The application of dielectric tests on stator winding water-cooled type has many problems. For instance, the polarisation effect in the winding cooling water adulterates the winding dielectric condition, resulting on low and inconsistent values for the insulation resistance and the polarisation index. The elevated conduction current through the winding cooling water does not allow the use of conventional instrumentation (megger). Additionally, still today the technical literature about this subject needs a consolidation. This paper presents a model for the stator winding water-cooled type and the procedure of the insulation resistance test used in the generating units of Itaipu Power Plant. This test procedure, based in the winding depolarisation, returns trustworthy results and reduces the test duration.