This study presents the short-term ageing study on refined, bleached and deodorised palm oil (RBDPO) and mineral oil (MO) in the presence of insulation paper, moisture, low molecular weight acid (LMA) and oxygen. The ageing experiment was performed for 7 days at 140°C. The oil was maintained dried while the paper’s moisture was varied between 0.5% and 3.5%. In total, 0.2 g of LMA and 20 mbar of oxygen pressure were initially introduced in the oil before the ageing started. Several analyses were conducted after the ageing experiment, which include the AC breakdown voltage (BDV) oil/paper, tensile strength, degree of polymerization (DP) and thermogravimetric analysis and differential scanning calorimetry (TGA-DSC). After being subjected to ageing in the presence of LMA and oxygen, the reduction of AC BDV of RBDPO is lower than MO at all moisture levels. At the same condition, the AC BDV of RBDPO-impregnated paper also maintains higher than MO-impregnated paper. The RBDPO-impregnated paper, in the presence of LMA and oxygen, has higher resistance toward ageing than MO-impregnated paper based on DP and tensile index, even in high moisture. All RBDPO are more resistant to ageing than MO in the presence of LMA and oxygen based on the high onset temperatures of the TGA-DSC analysis.

• Abdelmalik, A. A. (2015). Analysis of thermally aged insulation paper in a natural ester-based dielectric fluid. IEEE Transactions on Dielectrics and Electrical Insulation, 22(5), 2408-2414. https://doi.org/10.1109/TDEI.2014.004824

• Arroyo, O. H., Jalbert, J., Fofana, I., & Ryadi, M. (2017). Temperature dependence of methanol and the tensile strength of insulation paper: Kinetics of the changes of mechanical properties during ageing. Cellulose, 24(2), 1031-1039. https://doi.org/10.1007/s10570-016-1123-7

• ASTM D1816-12. (2019). Standard test method for dielectric breakdown voltage of insulating liquids using VDE electrodes. ASTM International. https://www.astm.org/Standards/D1816.htm

• ASTM D974. (2023). Standard test method for acid and base number by color-indicator titration. ASTM International. https://www.astm.org/d0974-22.html.

• ASTM D6304. (2021). Standard test method for determination of water in petroleum products, lubricating oils, and additives by coulometric karl fischer titration. ASTM International. https://www.astm.org/d6304-20.html

• ASTM D4243. (2023). Standard test method for measurement of average viscometric degree of polymerization of new and aged electrical papers and boards. ASTM International. https://www.astm.org/d4243-16.html

• Azis, N., & Wang, Z. D. (2011, August 22-26). Acid generation study of natural ester. [Paper presentation]. XVII International Symposium on High Voltage Engineering, Hannover, Germany.

• Azis, N., Jasni, J., Ab Kadir, M. Z. A., & Mohtar, M. N. (2014). Suitability of palm based oil as dielectric insulating fluid in transformers. Journal of Electrical Engineering and Technology, 9(2), 662-669. https://doi.org/10.5370/JEET.2014.9.2.662

• Carcedo, J., Fernández, I., Ortiz, A., Delgado, F., Renedo, C. J., & Pesquera, C. (2015). Aging assessment of dielectric vegetable oils. IEEE Electrical Insulation Magazine, 31(6), 13-21. https://doi.org/10.1109/MEI.2015.7303258

• Ciuriuc, A., Notingher, P. V., Jovalekic, M., & Tenbohlen, S. (2014, May 22-24). Experimental study on vegetable and mineral transformer oils properties. [Paper presentation]. International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), Bran, Romania. https://doi.org/10.1109/OPTIM.2014.6850907

• Coulibaly, M. L., Perrier, C., Beroual, A., & Marugan, M. (2012, September 23-27). Thermal aging of paper and pressboard in mineral and ester oils under air and nitrogen atmospheres. [Paper presentation]. IEEE International Conference on Condition Monitoring and Diagnosis, Bali, Indonesia. https://doi.org/10.1109/CMD.2012.6416449

• Emsley, A. M., Xiao, X., Heywood, R. J., & Aii, M. (2000). Degradation of cellulosic insulation in power transformers. Part 3: Effects of oxygen and water on ageing in oil. IEE Proceedings-Science, Measurement and Technology, 147(3), 115-119. https://doi.org/10.1049/ip-smt:20000021

• Ghoneim, S. S. M. (2021). The degree of polymerization in a prediction model of insulating paper and the remaining life of power transformers. Energies, 14(3), Article 670. https://doi.org/10.3390/en14030670

• Gomna, A., N’Tsoukpoe, K. E., Le Pierrès, N., & Coulibaly, Y. (2019). Review of vegetable oils behaviour at high temperature for solar plants: Stability, properties and current applications. Solar Energy Materials and Solar Cells, 200, Article 109956. https://doi.org/10.1016/j.solmat.2019.109956

• Ismail, N., Arief, Y. Z., Adzis, Z., Azli, S. A., Jamil, A. A. A., Mohd, N. K., Huei, L. W., & Kian, Y. S. (2013). Effect of water on electrical properties of refined, bleached, and deodorized palm oil (RBDPO) as electrical insulating material. Jurnal Teknologi (Sciences and Engineering), 64(4), 97-101. https://doi.org/10.11113/jt.v64.2108

• Kiasatina, Kamarol, M., Zulhilmey, M., & Arief, Y. A. (2011, June 21-22). Breakdown characteristics of RBDPO and soybean oil mixture for transformer application. [Paper presentation]. International Conference on Electrical, Control and Computer Engineering (InECCE), Kuantan, Malaysia. https://doi.org/10.1109/INECCE.2011.5953879

• Kouassi, K. D., Fofana, I., Cissé, L., Hadjadj, Y., Yapi, K. M. L., & Diby, K. A. (2018). Impact of low molecular weight acids on oil impregnated paper insulation degradation. Energies, 11(6), Article 1465. https://doi.org/10.3390/en11061465

• Maharana, M., Baruah, N., Nayak, S. K., Meher, N., & Iyer, P. K. (2019). Condition assessment of aged ester-based nanofluid through physicochemical and spectroscopic measurement. IEEE Transactions on Instrumentation and Measurement, 68(12), 4853-4863. https://doi.org/10.1109/TIM.2019.2900883

• Maharana, M., Nayak, S. K., & Sahoo, N. (2018). Karanji oil as a potential dielectrics liquid for transformer. IEEE Transactions on Dielectrics and Electrical Insulation, 25(5), 1871-1879. https://doi.org/10.1109/TDEI.2018.007230

• Makmud, M. Z.H., Illias, H. A., Chee, C. Y., & Sarjadi, M. S. (2018). Influence of conductive and semi-conductive nanoparticles on the dielectric response of natural ester-based nanofluid insulation. Energies, 11(2), Article 333. https://doi.org/10.3390/en11020333

• Makmud, M. Z. H., Illias, H. A., Chee, C. Y., & Dabbak, S. Z. A. (2019). Partial discharge in nanofluid insulation material with conductive and semiconductive nanoparticles. Materials, 12(5), Article 816. https://doi.org/10.3390/MA12050816

• Martin, D., Wang, Z. D., Darwin, A. W., & James, I. (2006, October 15-18). A comparative study of the chemical stability of esters for use in large power transformers. [Paper presentation]. IEEE Conference on Electrical Insulation and Dielectric Phenomena, Kansas City, USA. https://doi.org/10.1109/CEIDP.2006.311977

• Matharage, S. Y., Liu, Q., & Wang, Z. D. (2016). Aging assessment of kraft paper insulation through methanol in oil measurement. IEEE Transactions on Dielectrics and Electrical Insulation, 23(3), 1589-1896. https://doi.org/10.1109/TDEI.2016.005564

• Mohamad, N. A., Azis, N., Jasni, J., Kadir, M. Z. A. A., Yunus, R., Ishak, M. T., & Yaakub, Z. (2016). Investigation on the dielectric, physical and chemical properties of palm oil and coconut oil under open thermal ageing condition. Journal of Electrical Engineering and Technology, 11(3), 690-698. https://doi.org/10.5370/JEET.2016.11.3.690

• Mohamad, N. A., Azis, N., Jasni, J., Kadir, Z. A. A., Yunus, R., Ishak, M. T., & Yaakub, Z. (2015). Analysis on the degradation of insulation paper in palm oil and coconut oil under high temperature ageing. Jurnal Teknologi, 72(1), 1-6.

• Munajad, A., Subroto, C., & Suwarno. (2017). Study on the effects of thermal aging on insulating paper for high voltage transformer composite with natural ester from palm oil using fourier transform infrared spectroscopy (ftir) and energy dispersive x-ray spectroscopy (EDS). Energies, 10(11), Article 1857. https://doi.org/10.3390/en10111857

• N’cho, J. S., Fofana, I., Hadjadj, Y., & Beroual, A. (2016). Review of physicochemical-based diagnostic techniques for assessing insulation condition in aged transformers. Energies, 9(5), Article 367. https://doi.org/10.3390/en9050367

• Suwarno, & Pasaribu, R. (2017, September 11-15). Effects of Thermal Aging on Paper Characteristics in Paper-Mineral Oil composite Insulation. International Symposium on Electrical Insulating Materials (ISEIM), Toyohashi, Japan. https://doi.org/10.23919/ISEIM.2017.8166587

• IEEE Standars Associaltion. (2012). IEEE guide for loading mineraloil-immersed transformers and step-voltage regulators. IEEE Standars Associaltion. https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6166928

• Raj, R. A., Samikannu, R., Yahya Began, A., & Mosalaosi, M. (2020). Comparison of ageing characteristics of superior insulating fluids with mineral oil for power transformer application. IEEE Access, 8, 141111-141122. https://doi.org/10.1109/ACCESS.2020.3012988

• Raof, N. A., Yunus, R., Rashid, U., Azis, N., & Yaakub, Z. (2019). Effect of molecular structure on oxidative degradation of ester based transformer oil. Tribology International, 140, Article 105852. https://doi.org/10.1016/j.triboint.2019.105852

• Rapp, K. J., McShane, C. P., & Luksich, J. (2005, June 26- July 1). Interaction mechanisms of natural ester dielectric fluid and kraft paper. [Paper presntation]. IEEE International Conference on Dielectric Liquids (ICDL), Coimbra, Portugal. https://doi.org/10.1109/icdl.2005.1490108

• Raymon, A., Pakianathan, P., E. Rajamani, M. P., & Karthik, R. (2013). Enhancing the critical characteristics of natural esters with antioxidants for power transformer applications. IEEE Transactions on Dielectrics and Electrical Insulation, 20(3), 899-912. https://doi.org/10.1109/TDEI.2013.6518959

• RSPO. (2015). Impact Update 2015. Roundtable on Sustainable Palm Oil. https://www.helikonia.co.uk/wp-content/uploads/2020/12/FA-RSPO-Impact-Update-2015_SINGLE.pdf

• Sinan, S. S., Shawaludin, S. N., Jasni, J., Azis, N., Ab Kadir, M. Z. A., & Mohtar, M. N. (2014, May 23-23). Investigation on the AC breakdown voltage of RBDPO Olein. [Paper presentation]. IEEE Innovative Smart Grid Technologies - Asia (ISGT ASIA), Kuala Lumpur, Malaysia. https://doi.org/10.1109/ISGT-Asia.2014.6873888

• Suleiman, A. A., Muhamad, N. A., Bashir, N., Murad, N. S., Arief, Y. Z., & Phung, B. T. (2014). Effect of moisture on breakdown voltage and structure of palm based insulation oils. IEEE Transactions on Dielectrics and Electrical Insulation, 21(5), 2119-2126. https://doi.org/10.1109/TDEI.2014.004431

• Suryani, S., Sariani, S., Earnestly, F., Marganof, M., Rahmawati, R., Sevindrajuta, S., Indra Mahlia, T. M., & Fudholi, A. (2020). A comparative study of virgin coconut oil, coconut oil and palm oil in terms of their active ingredients. Processes, 8(4), Article 403. https://doi.org/10.3390/PR8040402

• Tripathi, A. K., & Vinu, R. (2015). Characterization of thermal stability of synthetic and semi-synthetic engine oils. Lubricants, 3(1), 54-79. https://doi.org/10.3390/lubricants3010054

• Vihacencu, M. Ş., Ciuriuc, A., & Dumitran, L. M. (2013). Experimental study of electrical properties of mineral and vegetable transformer oils. UPB Scientific Bulletin, Series C: Electrical Engineering, 75(3), 171-182.

• Wilhelm, H. ., Tulio, L., Jasinski, R., & Almeida, G. (2011). Aging markers for in-service natural ester-based insulating fluids. IEEE Transactions on Dielectrics and Electrical Insulation, 18(3), 714-719. https://doi.org/10.1109/TDEI.2011.5931057