THERMAL AGEING OF OIL IMPREGNATED PAPER FOR POWER TRANSFORMERS INSULATION SYSTEMS
Journal Title: ANALELE UNIVERSITATII DIN CRAIOVA - Seria Inginerie electrica - Year 2010, Vol 34, Issue 34
Abstract
The assessment of conditions and life time reserves of power transformers is generally done based on the analysis of characteristics of main components of insulation systems (oil and paper). During operation, the insulation systems of power transformers are subjected to different stresses (thermal, electrical, mechanical, other stresses); the most important for transformers operation are the thermal stresses which lead to degradation reactions of their insulation system. This paper presents a study concerning the ageing of some pressboard samples impregnated with NYNAS transformer oil subjected to accelerated thermal stress at the 155 ºC for time intervals between 0 and 750 h. For certain values of the real and the imaginary parts of complex conductivity and relative permittivity and the loss factor were measured for different values of the temperature and frequency. Variation curves of these quantities with ageing time were drawn. The results show that the increases of temperature and ageing time determine important increases of the real part of relative permittivity and real part of electrical conductivity and these increases are more important for low electric field frequencies. Using the values of real and imaginary parts of relative permittivity and conductivity and the loss factor the condition of oil impregnated paper can be obtained.
Authors and Affiliations
Laurenţiu BADICU, Petru NOTINGHER, Gabriel TĂNĂSESCU, Dorin POPA, Gheorghe BATIR
Keywords
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