Abstract
Operational factors are known to affect the health of an in-service power transformer and to reduce the capabilities and readiness for energy transmission and distribution. Hence, it is important to understand the degradation rate and corresponding behavioral aspects of different insulating fluids under various fault conditions. In this article, the behavior of mineral oil and two environmentally friendly fluids (a synthetic and a natural ester) are reported under arcing, partial discharges, and thermal fault conditions. Arcing, partial discharges and thermal faults are simulated by 100 repeated breakdowns, top oil electrical discharge of 9 kV for five hours, and local hotspots respectively by using different laboratory-based setups. Some physicochemical properties along with the gassing tendency of fresh and aged insulating liquids are investigated after the different fault conditions. UV spectroscopy and turbidity measurements are used to report the degradation behavior and dissolved gas analysis is used to understand the gassing tendency. The changes in the degradation rate of oil under the influence of various faults and the corresponding dissolved gasses generated are analyzed. The fault gas generations are diagnosed by Duval’s triangle and pentagon methods for mineral and non-mineral oils. It is inferred that; the gassing tendency of the dielectric fluids evolve with respect to the degradation rate and is dependent on the intensity and type of fault.
Highlights
Alternative dielectric fluids for use in oil-filled apparatuses is a topic of concern for industry and utilities for decades
The results of the degradation rate of the oil, before and after simulating electrical and thermal faults are discussed
When a fresh oil and aged oil are subjected to different fault conditions, the undergoing chemical perspectives are expected to the influenceSubsequently, is more associated to a generation acidson and free radicalsfluids whichwill leads the degradation
Summary
Alternative dielectric fluids for use in oil-filled apparatuses is a topic of concern for industry and utilities for decades. The tendency to gassing generation under partial discharges or low energy discharge electric faults in mineral oils and ester fluids were investigated and reported in [14,15,16]. Authors from our research group have reported the influence of aging on the gassing tendency and oil’s degradation under low energy electrical discharge faults for mineral oil and synthetic esters [23]. There is a need to study the gassing behavior of ester-based dielectric fluids (both natural and ester) under the influence of electrical and thermal fault conditions at different aging conditions and the influence of the faults on oil degradation. In the present work a mineral oil, a synthetic ester, and a natural ester have been investigated under low electrical energy discharge, high electrical energy arcing, and hotspot faulty conditions. The dissolved gas analysis measurements are performed as per ASTM D3612
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