Stator Winding Internal Thermal Monitoring and Analysis Using In Situ FBG Sensing Technology

This paper reports a novel thermal monitoring scheme for on-line internal temperature measurement in low-voltage random wound machine stator windings. The scheme is based on utilizing electrically nonconductive and electromagnetic interference immune fiber optic sensing technology embedded in close proximity of hot spots of interest to create a robust distributed thermal monitoring network within the machine windings. The key design and implementation features of the proposed system are presented and applied on a prototype mains-fed induction motor. The on-line thermal monitoring performance is examined in a number of typical continuous and periodic running duty tests, as defined by the relevant IEC standards for rating and performance of rotating electrical machines. It is shown that the presented scheme has the potential to provide competent on-line measurement of critical machine thermal hot spots that are largely beyond the effective reach of conventional thermal monitoring solutions. Furthermore, the proposed scheme underpins a higher fidelity understanding of the distribution and propagation of winding thermal stress, demonstrated by the experimental analysis reported in the paper.