Effect of Waiting Time on Concentration of Chemical Markers measured on Laboratory Ageing Samples

Laboratory scale thermal ageing experiments have been used not only to study the degradation of the insulation materials but also to understand the variation of chemical markers in liquid during the ageing process. However, trends obtained from different experiments often disagree with each other due to experimental variations such as material type, material ratio and ageing temperature. In addition to these well-known factors, there are lesser- known factors such as the duration for which samples are left at room temperature after an ageing experiment, which could affect the concentration of chemical markers in liquid. It is known that temperature could affect the partitioning of chemical markers among the liquid, solid and gas phase. Hence the concentration of certain chemical-markers in liquid could vary depending on the duration for which samples are left at room temperature prior to the sampling of oil for the measurements. This paper investigates the effect of this sampling period on the variation of chemical markers including water, methanol and ethanol in liquid after a laboratory scale ageing experiment conducted at 150 °C. Results showed that the concentration of the investigated chemical markers in liquid decrease continuously when the sample is left at room temperature, with water having the highest reduction followed by methanol and ethanol.