IntroductionTo carry out insulation reliability testing of hydropower generator stator windings, four testing methods have been periodically employed to determine whether o r not insulation withstanding the prescribed voltage level at the Tokyo Electric Power Company (TEPCO), is being maintaind.During these testings, much preparation time, which includes detachment and restoration of windings, wire connections of measuring equipment and data processing, was required. Particularly, for partial discharge measurement, expert operators were indispensable in achieving exact measurement. Furthermore, due to the lack of standardized measuring methods, various methods have been used by individual users and organizations.At TEPCO, personal-computer-aided automated measuring and data processing equipment have been developed and introduced for field use, thereby enabling all hydroelectric engineers to use this equipment with ease and confidence.[l], [21 With this equipment, about 20% and 25% reduction o f t e s t i n g t i m e a n d w o r k e r r e d u c t i o n s , respectively, were attained. In our newly developed automated equipment, a new partial discharge detector with low external noise was used.For rewinding the stator coils, comparison measuring tests employing both new and conventional discharge detectors were simultaneously carried out. The results attested to the excellent characteristics of the new detector, and variation response at each generating position of partial discharge in the windings was measured to a fairly accurate degree.
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