Chemical and physical properties of aged dodecylbenzene insulating oil

Oil plays an important role in many items of high voltage plant, both as an electrical insulator and as a coolant. Although the electrical properties of the oil degrade during use, an understanding of the ageing process is lacking. Consequentially samples of dodecylbenzene cable oil were aged thermally in various atmospheres at temperatures up to 135°C. The resulting samples were analyzed by a number of techniques to provide a comprehensive picture of the oil ageing process. The results highlight the effects of materials commonly found in high voltage plant, such as aluminium, paper and copper, and reveal the critical role of particular chemical species on oil ageing.