Copper particle contamination detection of oil-immersed transformer using laser-induced breakdown spectroscopy

The deterioration of transformer oil caused by particle contamination, especially copper particle, seriously affects the safe operation of oil-immersed transformers. Therefore, it is very important for the detection of metal particles in transformer oil. A new method based on laser-induced breakdown spectroscopy (LIBS) was first applied in the transformer oil diagnosis field. By screening out effective spots, the correlation between Cu particle concentration and LIBS signal was obtained after testing a set of oil samples with concentration range from 0.54 to 12.4 mu g/g; the calibration curves of Cu I 324.75 nm/CN 358.6 nm and Cu I 327.39 nm/CN 358.6 nm were therefore established. The results shown high linearity, and the determination coefficient R-2 of the two calibration curves in range from 0.54 to 3.1 mu g/g were superior to 0.99. The limit of detection (LOD) inferred from Cu I 324.75 nm/CN 358.6 nm fitting curve was 0.77 mu g/g and met the critical value specified by industry standards. Due to its flexibility, it can be used as a new-type of particle concentration detection method for transformer oil.