Kraft insulation paper
Ingredients
cellulose, hemicellulose, lignin
Preparation Steps
Original Recipe Text
The experimental procedure involved preparing oil-paper specimens for accelerated thermal ageing. Firstly, the naphthenic-based insulating oil and Kraft insulation paper were degassed and dehydrated separately in a vacuum-thermal chamber at 50 Pa and 80 °C for 48 h (p. 1588). Secondly, the insulation paper was impregnated with the insulating oil at 50 Pa and 60 °C for another 48 h. Thirdly, the well-processed insulating oil and paper were mixed and put into a stainless steel container with a mass weight ratio of oil to paper equal to 10:1 (p. 1588). A copper sheet with the dimension of 50×1.5×0.1 cm was submerged in the oil in each container to simulate transformer winding conditions. Lastly, the containers were sealed and put into an ageing chamber at temperatures of 120 and 130 °C for various durations ranging from 4 to 180 days (p. 1588-1589).
Evidence
"The Kraft insulation paper from Taizhou Xinyuan Electrical Equipment Co. Ltd. were used as the accelerated thermal ageing experiment materials. (p. 1588) ... The insulation paper used in transformers consists of about 90% cellulose by weight, and others include hemicellulose and lignin. (p. 1589)"
Remarks
This study focuses on characterizing the degradation of transformer paper insulation using the dispersion staining method (DSM). The paper establishes that the refractive index of cellulose fibers increases as they age (p. 1590). These changes are visually manifested through dispersion staining colors (DSCs); unaged fibers appear mainly blue, indicating low refractive indices, but shift toward purple, then red or orange as the ageing degree (and refractive index) increases (p. 1592, 1595). The study correlates these optical changes with the average degree of polymerization (DP) and crystallinity index (Cr). Crystallinity was found to increase rapidly in the early ageing stage and more slowly later on (p. 1590). The research proposes primary color ratio-based markers (PCR-R and PCR-MD) which demonstrate potential for predicting the residual life of paper insulation in oil-filled transformers (p. 1595).