Locating of leaks in water-cooled generator stator bars using perfluorocarbon tracers

Technical Report · Sun Sep 01 04:00:00 EDT 1991

DOI:https://doi.org/10.2172/6081483· OSTI ID:6081483

Loss, W M; Dietz, R N

Water cooled stator bars in power plant generators often fail during the maintenance cycle due to water leakage. After the hydrogen pressure in the generator shell has been released water can leak through cracks in the copper and through the insulation. Leaking bars, but not the leaks themselves, are detected with so-called hi-pot'' (high potential) tests where direct electrical current is applied to the stator bar windings. A study initiated by ConEd and Brookhaven's Tracer Technology Center to explore the cause of these leakage problems to determine if the failures originate in the manufacturing process or are created in service by phase related torque stresses. To this purpose bars that had failed the hi-pot test were investigated first with the insulation in place and then stripped to the bare copper. The bars were pressurized with gases containing perfluorocarbon tracers and the magnitude and location of the leaks was detected by using tracers technology principles and instruments such as the double source'' method and the Dual Trap Analyzer. In the second part of the project the windings within a generator were tested in-situ for leaks during an outage using tracer principles. Recommendations are given suggesting the shut down of stator bar cooling water before hydrogen bleeding during outages and a revision of the current vent flow rate. The new standard should establish a reasonable leak rate for the stator bar windings proper and exclude leakage of pump seals and connections. Testing during the maintenance cycle in generators should include routine tracer leak detection following the hi-pot test.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6081483
• Report Number(s): BNL-46745; ON: DE92005006
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220200* -- Nuclear Reactor Technology-- Components & Accessories
COOLING
DETECTION
FAILURES
FLUORINATED ALIPHATIC HYDROCARBONS
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LEAKS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXYGEN COMPOUNDS
STATORS
TRACER TECHNIQUES
WATER