Investigation on aging markers of thermally accelerated aged oil-impregnated papers

Summary

With the liberalization of the electricity market, the operators of energy supply are more and more interested to prolong the life of their assets, which results in replacing the high voltage components later and later. Accordingly, the imposed cost pressure could be mitigated. This could results in increased stress on insulation of high voltage equipment, which makes them more vulnerable to different failures. The life of a high voltage component decisively depends on the condition of the insulation system. Oil impregnated paper are widely used as insulation material for high voltage apparatus such as oil-filled power transformers or reactors. Both paper and oil insulation have a slow but steady aging process under thermal, electrical, mechanical and chemical stresses. However, the effect of temperature has a decomposing effect on the cellulose of the paper, resulting in a decrease of the mechanical stability of the paper as well of its insulation quality. In order to prolong the life duration of the paper-insulation and to give recommendations about their future life expectation it is necessary to observe the degeneration of the cellulose during operation time of the asset. In general, this is been done by measuring various kinds of monitoring parameters by investigating the oil insulation. But there is a high level of experience need to predict the actual condition of the cellulose, due to these measuring results. Therefore, a study was conducted to investigate the change of the paper (degeneration) during long-term thermal stress. The aim of this research is the development of an assessment scheme for the estimation of the aging progress of oil-paper insulation as a function of characteristic parameters, such as the stress time. The focus of these investigations is the finding of aging mechanisms that are suitable for the formulation of a condition statement of the paper with increased thermal stress and whether these occur sufficiently in the insulation system.

Additional informations

Keywords

decomposition, paper aging, aging marker