Impulse strength of distribution transformers under load. Final report, February 1975--September 1976
The General Electric Company was contracted by the Energy Research and Development Administration (ERDA) under contract No. E(49-18) 2157 to study the relationship in distribution transformers between impulse strength and load current. The evaluation of the impulse strength of distribution transformers by a new test technique which simulates in-service functional conditions is described. This unique test procedure includes the effect of different load currents and of rated 60 Hz voltage stress as well as the effect of precipitation cooling. Over 50 distribution transformers with a 15 kV class insulation system were subjected to impulse breakdown tests; approximately one half of these transformers were tested in the new condition. The other half were tested after a loss of life of 50% during accelerated laboratory aging. Specimen transformers representing several USA manufacturers were purchased from five utility stockpiles. The possibility that gas bubble formation and/or accumulation within transformer windings may be a factor contributing to transformer field failures was the subject of another study described. Visual observation and dielectric measurements were made on full-size distribution transformers and on special model coils in order to establish operating conditions which resulted in bubble generation and a possible decrease in insulation breakdown strength. Other data obtained during the aging and loading of sample transformers includes: excitation and impedance losses before and after aging; winding temperatures and estimated hot spot temperatures as a function of load current; and oil characteristics before and after aging. Also described are the results of impulse tests under short-time overload conditions, and some data concerning the effect of moisture in the winding on impulse breakdown.
- Research Organization:
- General Electric Co., Pittsfield, MA (USA)
- DOE Contract Number:
- EX-76-C-01-2157
- OSTI ID:
- 7099559
- Report Number(s):
- CONS-2157-1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
TRANSFORMERS
PERFORMANCE TESTING
AC SYSTEMS
AGING
BREAKDOWN
BUBBLES
ELECTRIC POWER
ELECTRICAL INSULATION
ENERGY CONSERVATION
MOISTURE
POWER DISTRIBUTION
SURGES
TEMPERATURE DEPENDENCE
ELECTRICAL EQUIPMENT
EQUIPMENT
POWER
POWER SYSTEMS
TESTING
200301* - Power Transmission & Distribution- AC Systems
EHV & UHV- (-1989)