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In this paper the results of an experimental study concerning the vegetable and mineral oil impregnated paper subjected to thermal ageing is presented. Using activation energy method, the paper lifetime is calculated. Samples of vegetable and mineral oil impregnated paper were aged at 155 °C. Dielectric properties, water content and degree of polymerization of aged samples were measured. Using the...
The electrical field causes a series of stresses on the power transformers' insulation systems, respectively over voltages, surface electrical discharges on the solid components' surfaces, partial discharges etc. All these stresses (permanent and temporary) are more important for high electrical field strength and they cause insulation's degradation and loss of life. Among these, partial discharges...
In the last years, the vegetable oil for power transformers has attracted much interest from the manufacturers and users of power transformers especially due to its superior fire point and biodegradability. In this paper an experimental study regarding the properties of vegetable and mineral oils subjected to thermal stress (155 °C, 1500 h) in the presence and absence of paper is presented. During...
The power transformer's lifetime is strongly influenced by its insulation system degradation, especially by the paper degradation. As the vegetable oil should replace mineral oil, this paper presents a study concerning the dielectric properties variation of cellulosic paper impregnated with vegetable oil as a function of the ageing duration. In order to characterize the condition of the paper the...
The operational safety of transmission and distribution grids depends essentially on the power transformers' state. Lately, there is a tendency to replace mineral oils with vegetable oils because vegetable oils provide a higher explosion safety aspect for transformers due to their higher fire points. Further, vegetable oils are favorable for the environment due to their higher biodegradability. The...
Due to the increasing need to replace the petroleum based products, there's an interest in replacing the mineral insulating oil for electrical equipment with biodegradable vegetable oil. This paper presents a comparative experimental study concerning the ageing of mineral and vegetable oils used in power transformers. In this view, samples of mineral and vegetable oil were accelerated thermally aged,...
The flow electrification of mineral oil produces local electric discharges which may facilitate the damage and worsen the physico-chemical properties of the electrical power transformer insulation systems. This paper presents a study concerning the influence of the mineral oil ageing condition on the flow electrification phenomenon. The flow electrification current has been measured with a spinning...
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