Experimental Study on Thermal Aging Characters of Silicone Oil in Cable Terminal

In order to actualize the safe and reliable operation of transmission lines, it is necessary to carry out research on cable latent faults, so as to grasp the operation characteristics of cables under different fault conditions. This focuses on the thermal aging problem of silicone oil in cable terminal caused by long-term heating. The testing oil were placed in sealed pots and were thermal aging in a heating oven for 90 days at three different conditions, i.e. 30 °C, 60 °C and 90 °C. The electrical and physicochemical properties were tested to study the degradation level of the oil, and the infrared spectrum characters are tested to identify the presence of new substances. The experiments showed that the speed of degradation of silicone oil is very slow under limited thermal aging temperature (lower than 60 °C in this study) and test time. When the temperature is further raised to 90 °C, the aging process of silicone oil is accelerated. The acid value and kinematic viscosity increase, but the fluctuation range is not obvious. The whole aging process is accompanied by water generation. In addition, from the infrared spectrum results, the long chain molecule of silicone oil breaks down under the condition of thermal aging, which makes the side chain -CH
₃
separate from the main chain of Si-O and forms a new impurity component.