Oil-filled submarine cables play a crucial role in long-distance and high-voltage power transmission. However

the damage of cable will lead to the leakage of insulating oil and can impair the safety of power transmission. In order to detect trace insulating oil in the sea and thus precisely locate the leakage points of submarine cables

we developed a micro-detection device for the insulating oil of submarine cables based on the ultraviolet fluorescence method

and explained the detection principle of the ultraviolet fluorescence method for insulating oil. Moreover

the mechanical structure

optical path

core components

and circuits of the detection device were designed. The optimization schemes for the laboratory and field applications of the detection device were proposed. The concentration of insulating oil was calibrated

proving that the detection device has an accuracy rate of over 90% and a detection limit as low as 0.375 μg/L. The corrections of turbidity and temperature were carried out and the correction algorithms for turbidity and temperature were determined. The long-term field stability test in the Pearl River was carried out

proving that the prototype can operate stably for a long time and the temperature has a negligible effect on the fluorescence intensity. The simulated insulating oil leakage test in the Qiongzhou Strait was carried out. It is found that the insulating oil concentration exceeding 860 μg/L is detected at 0.5 m above the leakage point

enabling precise localization of the insulating oil leakage point

which is of great significance for the operation and maintenance of oil-filled submarine cables.