Bubble generation during transformer overload

Technical Report · Thu Mar 01 00:00:00 EST 1990

OSTI ID:6975814

Oommen, T V ^[1]

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1. Westinghouse ABB Power T and D Co., Sharon, PA (USA). Materials and Mfg. Technology Dept.

Bubble generation in transformers has been demonstrated under certain overload conditions. The release of large quantities of bubbles would pose a dielectric breakdown hazard. A bubble prediction model developed under EPRI Project 1289-4 attempts to predict the bubble evolution temperature under different overload conditions. This report details a verification study undertaken to confirm the validity of the above model using coil structures subjected to overload conditions. The test variables included moisture in paper insulation, gas content in oil, and the type of oil preservation system. Two aged coils were also tested. The results indicated that the observed bubble temperatures were close to the predicted temperatures for models with low initial gas content in the oil. The predicted temperatures were significantly lower than the observed temperatures for models with high gas content. Some explanations are provided for the anomalous behavior at high gas levels in oil. It is suggested that the dissolved gas content is not a significant factor in bubble evolution. The dominant factor in bubble evolution appears to be the water vapor pressure which must reach critical levels before bubbles can be released. Further study is needed to make a meaningful revision of the bubble prediction model. 8 refs., 13 figs., 11 tabs.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (USA); Westinghouse ABB Power T and D Co., Sharon, PA (USA). Materials and Mfg. Technology Dept.
• Sponsoring Organization: EPRI
• OSTI ID: 6975814
• Report Number(s): EPRI-EL-6761
• Country of Publication: United States
• Language: English

Related Subjects

24 POWER TRANSMISSION AND DISTRIBUTION
42 ENGINEERING
36 MATERIALS SCIENCE
BUBBLES
DIELECTRIC PROPERTIES
POWER DISTRIBUTION SYSTEMS
TRANSFORMERS
BREAKDOWN
COMPARATIVE EVALUATIONS
CONSTRUCTION
DESIGN
ELECTRICAL INSULATION
HAZARDS
IMPREGNATION
OPERATION
OVERCURRENT
PRESSURE EFFECTS
RECOMMENDATIONS
SURFACE TENSION
TEMPERATURE EFFECTS
THERMOCOUPLES
VAPORS
VARIATIONS
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
EQUIPMENT
FLUIDS
GASES
MEASURING INSTRUMENTS
PHYSICAL PROPERTIES
SURFACE PROPERTIES
240201* - Power System Networks
Transmission & Distribution- AC Systems- (1990-)
426000 - Engineering- Components
Electron Devices & Circuits- (1990-)
360602 - Other Materials- Structure & Phase Studies