A Portable NMR Sensor Used for Assessing the Aging Status of Silicone Rubber Insulator

A portable nuclear magnetic resonance (NMR) sensor with an adjustable ‘clamp’ structure is constructed for the noninvasive measurement of the aging status of silicone rubber insulators used in the high-voltage power transmission. The Carr–Purcell–Meiboom–Gill sequence was employed to record the ¹H NMR transverse relaxation curves of silicone rubber insulators with different service times. The decay curves were fitted to mono-exponential and bi-exponential functions. Further data processing of the decay curves was performed with the inverse Laplace transformation for one-dimensional T ₂ distribution analysis, focusing on the mean lifetime of the long T ₂ component (T _{2long mean}). The results demonstrate that an increase in the aging level of the insulator clearly results in a decrease of T _{2long mean}. For comparison, the relative permittivity of the insulator was also measured. It shows the same trend as that of T _{2long mean}. This indicates that the T _{2long mean} relaxation time obtained from our portable NMR sensor can reliably be used as an index to reflect the aging status of silicone rubber insulator.