Application of Fluorescence Spectrophotometry in Trace Contamination Detection of Insulating Oil for Submarine Cables

Oil-filled cables are identified as critical infrastructure for cross-regional energy interconnection, and their insulating oil leakage poses a potential threat to marine ecosystems. In complex marine environment, widespread presence of background oils, such as diesel, significantly interferes with specific identification and accurate quantification of insulating oil leakage. The study focused on a coexistence system of typical submarine cable insulating oil (dodecyl benzene insulating oil) and typical diesel (Sinopec No.0 diesel). Differences in oil composition were analyzed via gas chromatography-mass spectrometry (GC-MS), and fluorescence spectral response characteristics of single and mixed oils in various medium environments were systematically investigated. Results showed that under excitation/emission wavelengths (λ_ex/λ_em) of 220 nm/295 nm, fluorescence signals of insulating oil and diesel could achieve baseline separation. Based on this characteristic wavelength, quantitative models were established for single submarine cable insulating oil and for insulating oil in the presence of diesel interference. It was found that seawater medium had no significant impact on these quantitative models. The proposed fluorescence detection method was characterized by its rapidity, sensitivity, and strong anti-interference capabilities, providing reliable technical support for online monitoring and precise early warning of insulating oil leakage in submarine cables under complex marine conditions.