A Graphitic Carbon Nitride Film Capacitive Sensor for Selective Trace Moisture Detection in Transformer Oil

Transformers play a vital role in the power system. Moisture, 2-furfuraldehyde (2-FAL), and dissolved gases in transformer oil are used to assess the condition of the insulation in transformers. Reliable transformer insulation health monitoring in real time is still a challenge. Sensorbased monitoring is one of the solutions. The moisture concentration in oil is an important indicator of the health of oil and article insulation as well as an in-service transformer. Although it is possible to measure moisture concentrations in transformer oil using a capacitive sensor as its dielectric constant is very high in comparison to the oil, at the same time, the capacitive sensor will be sensitive to another high dielectric constant contamination, 2-FAL. Therefore, sensitive and selective measurement of the concentration of moisture in oil is a challenge. In this work, a novel material with an optimized comb structure is presented for selective trace moisture detection. A graphitic carbon nitride (g- C3N4) film capacitive sensor for moisture detection in transformer oil has been presented. This work aims to develop a robust and precise sensor for on-site condition monitoring, with an emphasis on material selection, design, and accurate characterization. The proposed sensor is tested for mineral and palm oil samples that contain different moisture concentrations from 0 to 40 ppm. The cross-sensitivity of the sensor is determined with 2-FAL and it is found that it is highly selective for moisture. The proposed sensor is found to be highly sensitive and selective for moisture detection in oil.