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In this paper, the electrical resistivity (determined with absorption/resorption currents) is used as a diagnostic factor in order to assess the mineral oil condition and to evaluate its elapsed and remaining lifetimes. Based on experimental results of thermal accelerated ageing, the lifetime values at constant temperature are calculated by the IEC and activation energy methods. The chosen end-of-life...
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 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...
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