Optimal Design of a Portable Arc-Shaped NMR Sensor and Its Application in the Aging-Level Detection of Silicone Rubber Insulator

Resumo

Silicone rubber insulators (SRIs) are widely used in power systems because of their excellent hydrophobicity, high mechanical strength, and light weight; however, detecting SRI degradation remains problematic. Many studies have focused on SRI detection, but reports on rod-sheath detection are limited. We designed a novel nuclear magnetic resonance sensor that could be used to detect the sheath of arc-shaped SRI rods. First, the magnetic structure that generates the main magnetic field (B₀) was designed and optimized, and B₀ was designed purposely for an arc-shaped distribution that can match the sheath of SRI rod well. Second, an arc-shaped spiral radio-frequency coil was designed and optimized. Third, three SRIs serving on a 220-kV power transmission line for different time points were measured using this sensor. The transverse-relaxation decay curves were obtained using the Carr–Purcell–Meiboom–Gill (CPMG) sequence. Inverse Laplace transformation was then used to obtain the T₂ distribution from the CPMG decay curves. T₂ distribution demonstrated that the long component of T₂ decreased with increased serving time. Therefore, the T_{2,long mean} obtained from the T₂ distribution can be used as an index to reflect the aging level of the sheath of SRI rod.