Ageing of thermally and electrically stressed mineral oil impregnated presspaper insulation systems

Muth, Torben; Jenau, Frank; Gasser, H.P.

doi:10.1109/ichve.2014.7035388

Cited by 1 publication

(1 citation statement)

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“…The ability of the insulation systems based on impregnated cellulose materials to work reliably depends on their current degree of aging. If the degree of polymerization of cellulose, which correlates with mechanical strength [1], is taken as the measure of aging, then in the case of typical exposures occurring in the transformer (temperature, electric field strength, and mechanical stresses), the aging process will depend on the combination of these exposures [2]. By reproducing thermal and electrical exposures in laboratory conditions, it can be proved that thermal exposures are dominant [3].…”

Section: Introductionmentioning

confidence: 99%

The Use of Methanol Vapour for Effective Drying of Cellulose Insulation

Przybyłek

Gielniak

2023

Energies

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The paper deals with a new method of drying cellulose insulation, which uses methanol vapour present in nitrogen as a drying medium. Compared to the insulation drying methods currently used in the industry, the method presented in the article has the following advantages: there is no cellulose depolymerization because there is no need to heat the insulation, there is no need to use large-size and energy-intensive dryers because the whole process takes place in the tank of the transformer. Important parameters of the drying process, such as methanol concentration in the nitrogen, flow rate, and process duration, were determined in four separate experiments. For the purposes of these experiments, a special system was constructed to control and measure the flow of drying medium. Controlling the flow rate of the carrier gas (nitrogen) made it possible to obtain different concentrations of methanol in nitrogen. Such values of concentration and flow rate were determined that allow drying of pressboard and paper in less than 144 h to a level lower than 1%.

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Section: Introductionmentioning

confidence: 99%