A New Approach Toward Assessing Transformer Insulating Paper Condition via Online Optical Detection of 2-FAL

A feasibility check of a novel optical chemical sensor for the detection of 2-Furaldehyde (2-FAL) in an insulating liquid under flow is reported. The device consists of a capturing chip made in a plastic optical fiber (POF), which houses a robust, cheap and stable synthetic receptor with high selectivity and sensitivity to the specific 2-FAL chemical marker. The interrogation scheme is based on a white light source and on a POF-based resonant detector, which can be located away from the POF-based capturing chip. To reproduce a real operating conditions tests were carried out on a laboratory mockup which replicates the expansion tank (conservator) of an insulating liquid filled transformer. Increasing 2-FAL amounts were manually injected into the tank and driven to the measuring cell. Results indicate that the optical device can rapidly follow the increase of 2-FAL amounts in the conservator (up to 0.5 mg/L concentrations), confirming the feasibility of the application of this device for dynamic detection of 2-FAL in the tank.