Abstract
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 T2 distribution analysis, focusing on the mean lifetime of the long T2 component (T2long mean). The results demonstrate that an increase in the aging level of the insulator clearly results in a decrease of T2long mean. For comparison, the relative permittivity of the insulator was also measured. It shows the same trend as that of T2long mean. This indicates that the T2long 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.
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