D-Shaped Photonic Crystal Fiber SPR Sensor for Humidity Monitoring in Oils

¹ Federal University of Pará, Applied Eletromagnetism Laboratory, Belém Pará, Brazil
² Federal Center for Technological Education Celso Suckow da Fonseca, Rio de Janeiro, Brazil
³ Military Institute of Engineering, Rio de Janeiro, Brazil
⁴ INESC TEC, Porto, Portugal
⁵ Faculty of Sciences, University of Porto, Porto, Portugal

^* Corresponding Author: Romeiro.amanda@gmail.com

Published online: 15 October 2024

Abstract

This theoretical study presents a D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) based sensor designed for humidity detection in transformer oil. Humidity refers to the presence of water dissolved or suspended in the oil, which can affect its dielectric properties and, consequently, the efficiency and safety of the transformer’s operation, failures in the sealing system and the phenomenon of condensation can be the main sources of this humidity. This sensor leverages the unique properties of the coupling between surface plasmons and fiber guided mode at the Au-PCF interface to enhance the sensitivity to humidity changes in the external environment. The research demonstrated the sensor’s efficacy in monitoring humidity levels ranging from 0% to 100% with an average sensitivity of measured at 1106.1 nm/RIU. This high sensitivity indicates a substantial shift in the resonance wavelength corresponding to minor changes in the refractive index caused by varying humidity levels, which is critically important in the context of transformer maintenance and safety. Transformer oil serves as both an insulator and a coolant, and its humidity level is a key parameter influencing the performance and longevity of transformers. Excessive humidity can lead to insulation failure and reduced efficiency and, therefore, the ability to accurately detect and monitor humidity levels in transformer oil can significantly enhance preventive maintenance strategies, reduce downtime, and prevent potential failures, ensuring the reliable operation of electrical power systems.