Abstract
Transformer explosion and its prevention is a complex industrial issue where various physical phenomena occur. To understand them, an experimental test campaign was performed by CEPEL on large scale transformers. It consisted in creating arcing in oil filled transformer tanks. The tests confirmed that the arc generates dynamic pressure waves that propagate in the oil. Reflections of these waves on the walls build up high static pressure to which transformer tanks can not withstand. This static pressure increase can be prevented by a quick oil evacuation triggered by the first dynamic pressure peak generated by the electrical arc. Moreover, a numerical tool was developed to simulate the phenomena highlighted during the tests and mainly the pressure wave propagation. It is thus based on a compressible two-phase flow modelling where viscous flow, electromagnetic, thermal and gravity effects are taken into account. The equations are solved using a finite volume method allowing computing complex 3D transformer geometries. Comparisons between the data obtained during the experiments and the results given by the simulations validated the model. It can be used to study transformer explosions as well as depressurisation induced by the explosion prevention technology based on a quick oil evacuation.
Highlights
Companies often reduce the investments by using aging equipments and by overloading the power transformers
Explosions were found to occur when the transformer oil loses its dielectric properties leading to the occurrence of an electrical arc inside the transformer tank
PAPER CONTENTS The aim of this paper is to present the development of such a numerical tool able to describe unsteady non uniform pressure phenomena following the arc ignition and the influence on the pressure distribution of a mechanical device that evacuates the oil in order to prevent the explosion
Summary
Companies often reduce the investments by using aging equipments and by overloading the power transformers. Oil-filled transformer explosions are more and more frequent and they result in dangerous fires, very expensive damages and possible environmental pollution. For all these reasons, transformer explosions and their prevention are becoming a critical industrial issue. Explosions were found to occur when the transformer oil loses its dielectric properties (because of age, Pressure wave propagation induced by short circuits inside power transformers: Development of a simulation tool, comparisons with experiments and applications design errors, oil pollution, overloading, lack of maintenance...) leading to the occurrence of an electrical arc inside the transformer tank
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