Improvements in corona probe testing of modern hydroelectricgenerators

摘要

The authors reevaluate the required test voltage, necessarystabilization time, and traditional measurement frequencies for coronaprobe testing. Studies indicate that the corona inception voltage (CIV)can be estimated for each stator slot. When a coil is operated below itsCIV, deterioration due to electrical discharges is very unlikely. Thiswas verified through dissection of several coils. Data were compiledfrom tests performed on four machines with epoxy-mica insulation systemsat service ages of 10000, 50000, and 200000 h