Further experimentation on bubble generation during transformer overload
- ABB Transmission Technology Inst., Raleigh, NC (United States)
This report covers additional work done during 1990 and 1991 on gas bubble generation under overload conditions. To improve visual bubble detection, a single disc coil was used. To further improve detection, a corona device was also used which signaled the onset of corona activity in the early stages of bubble formation. A total of fourteen model tests were conducted, half of which used the Inertaire system, and the remaining, a conservator (COPS). Moisture content of paper in the coil varied from 1.0% to 8.0%; gas (nitrogen) content varied from 1.0% to 8.8%. The results confirmed earlier observations that the mathematical bubble prediction model was not valid for high gas content model with relatively low moisture levels in the coil. An empirical relationship was formulated to accurately predict bubble evolution temperatures from known moisture and gas content values. For low moisture content models (below 2%), the simple Piper relationship was sufficient to predict bubble evolution temperatures, regardless of gas content. Moisture in the coil appears to be the key factor in bubble generation. Gas blanketed (Inertaire) systems do not appear to be prone to premature bubble generation from overloads as previously thought. The new bubble prediction model reveals that for a coil with 2% moisture, the bubble evolution temperature would be about 140{degrees}C. Since old transformers in service may have as much as 2% moisture in paper, the 140{degrees}C bubble evolution temperature may be taken as the lower limit of bubble evolution temperature under overload conditions for operating transformers. Drier insulation would raise the bubble evolution temperature.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); ABB Transmission Technology Inst., Raleigh, NC (United States)
- Sponsoring Organization:
- EPRI; Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 5281049
- Report Number(s):
- EPRI-EL-7291
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AC SYSTEMS
POWER SUBSTATIONS
ELECTRICAL INSULATION
BUBBLES
TRANSFORMERS
DIELECTRIC MATERIALS
GASES
MATHEMATICAL MODELS
MOISTURE
NITROGEN
POWER TRANSMISSION
TESTING
VAPOR PRESSURE
ELECTRICAL EQUIPMENT
ELEMENTS
EQUIPMENT
FLUIDS
MATERIALS
NONMETALS
PHYSICAL PROPERTIES
POWER SYSTEMS
THERMODYNAMIC PROPERTIES
240201* - Power System Networks
Transmission & Distribution- AC Systems- (1990-)