A new diagnostic tool for determining and locating wet electrical insulation

Leaking water coolant into stator electrical insulation is a growing concern for the aging liquid-cooled generator fleet since wet insulation poses a safety risk to continued operation. Present leak detection or monitoring methods suffer from one or more weaknesses: lack of locational specificity, poor sensitivity or selectivity, and/or inability to be implemented on-line. A new technology has been developed to address these needs (the "Wet Bar Detector" (WBD)). This report will briefly discuss the background of the water-leak problem and provide a brief survey of the present technology commercially available for detecting and/or monitoring water leaks or wet insulation. Next, a statistical analysis and comparison is presented benchmarking the performance of the WBD versus capacitance mapping. A prototype field instrument has been built and beta-testing is underway (off-line) on generators with suspected water coolant leak problems. Preliminary field data is presented.