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Frequency domain spectroscopy (FDS) is widely used to diagnose the condition of transformer oil–paper insulation. However, FDS measurements are highly temperature dependent. The master curve technique is the most common method to remove the temperature effect on FDS, but the reliability of this method is largely dependent on the value of the activation energy, which can be affected by moisture content...
The cellulosic insulation used in electrical transformers were aged in mineral oil and natural ester respectively to investigate the influence of oil type on thermal ageing properties of oil-paper. The accelerated ageing test was developed at three different temperatures and degree polymerization (DP) of insulation paper was measured to indicate the ageing extent of paper. Furfural concentration CF...
In order to compare the characteristics of natural ester impregnated Kraft paper and thermally upgraded paper, sealed aging vessels containing copper, insulation paper (Kraft paper and thermally upgraded paper), and natural ester were aged at 90, 110, and 130degC about 400 days. The results show that both degree of polymerization (DP) and leveling-off degree of polymerization (LODP) for thermally...
The accelerated thermal experiments at 90degC, 110degC and 130degC are performed, using the samples that Kraft paper or thermally upgraded paper were immersed by mineral oil or nature ester. The results show that the leveling-off degree of polymerization (LODP) for ester-immersed paper insulation is higher than the one for mineral oil-immersed paper insulation, and the time of getting to the LODP...
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