Aging of silicone rubber composite insulators widely used in high-voltage transmission lines is a dynamic process starting from surface and gradually forming an aged surface layer with reduced thermal diffusivity. Based on the demodulation of the modulated infrared radiation signal and the subsequent data analysis, self-normalized photothermal radiometry (PTR) is used to quantitatively characterize the aging degree of field-serviced composite insulators. The ratio of the thermal diffusivity of the aged layer normalized by the substrate thermal diffusivity is proposed to characterize the aging degree to eliminate the influence of the wide variation of the initial thermal diffusivities of fresh silicone rubber composite insulators which are normally not known. Experimental results show that the thermal diffusivity ratio decreases and the aged layer thickness increases monotonically with the increasing field-service years, in consistent with the measurements of hydrophobicity class. The thermal diffusivity ratio and thickness of the aged layer are expected to be used as numerical indices for understanding the aging mechanism and estimating the remaining lifetime of silicone rubber composite insulators in field service.

高压输电线路中广泛使用的硅橡胶复合绝缘子的老化是一个动态过程，其过程从表面开始，逐渐形成具有降低的热扩散率的老化表面层。基于已调制红外辐射信号的解调和后续数据分析，使用自归一化光热辐射法（PTR）定量表征现场维修的复合绝缘子的老化程度。提出了通过基底热扩散率归一化的老化层的热扩散率之比，以表征老化程度，以消除通常未知的新鲜硅橡胶复合绝缘子的初始热扩散率的广泛变化的影响。实验结果表明，随着疏水性等级的增加，热扩散率降低，老化层厚度随现场使用年限的增加而单调增加。预期热扩散率和时效层的厚度将用作数值指标，以了解时效机理并估计现场使用中的硅橡胶复合绝缘子的剩余寿命。