Abstract
This study explores the influence of hydrostatic pressure on the discharge along the oil-paper interface under AC voltage, especially for the normal operating condition and breakdown. In this paper, an experimental platform was set up to record the partial discharge (PD) parameters of the test sample under different hydrostatic pressures, while the applied AC voltage was increased to final flashover voltage step by step. Experimental results showed that higher hydrostatic pressure had different effects on PD under different voltages. Higher pressure decreased the PD energy and increased the flashover voltage. Furthermore, under higher hydrostatic pressure, discharge traces (white mark) were found on the surface of the samples after intense discharging on the oil-paper interfaces, indicating that the hydrostatic pressure can affect the gas generation and dissipation process underneath the surface of the pressboards. Finally, the mechanism of how hydrostatic pressure influences the PD, flashover voltage, and white mark was interpreted based on the bubble theory. The results derived in this paper can be helpful for an optimal design and reasonable operation of oil-paper insulation systems, especially for power transformers.
Highlights
The phenomenon of surface discharge is widespread in the field of electrical engineering and has been studied by many scholars [1,2,3,4,5,6,7]
PD charge, and PD energy into consideration to analyze the influence of hydrostatic pressure on partial discharge
This paper mainly focuses on the voltage stages when PD was not over 200 pC under atmospheric pressure (17–25 kV), to study the effect of pressure on the oil-paper interface PD under the normal operating condition
Summary
The phenomenon of surface discharge is widespread in the field of electrical engineering and has been studied by many scholars [1,2,3,4,5,6,7]. When the local electrical field is intensified by degradations like moisture, dielectric degradation, or winding deformation, discharge may happen along the paper interface. Sustained PD induces unrecoverable tracking and carbonization on the pressboard [1,2]. This kind of dielectric degradation will cause flashover along the surfaces, winding short-circuit, and even bushing burst. The surface discharge in oil-paper insulation has been studied from different aspects [1,2,9,10,11,12,13]
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