Temperature Monitoring for 500 kV Oil-Filled Submarine Cable Based on BOTDA Distributed Optical Fiber Sensing Technology: Method and Application

The 500 kV oil-filled ac submarine cables in the networking project of China's southern coast are large capacity, ultrahigh-voltage cross-sea submarine power cables, which are 31 km long and bundled with submarine optical cables. Temperature monitoring on submarine cables is of great significance in controlling the ampacity and ensuring operational reliability. Referring to the submarine cables' structural characteristics and setting conditions, a temperature monitoring system is established based on the Brillouin optical time-domain analysis (BOTDA) distributed optical fiber sensing technology. The thermal circuit model IEC60287 is modified and used to calculate internal temperature distribution. Moreover, an onshore simulation experimental platform is established on the same cables as the networking project with a special sealing and joint structures designed for filling oil and adding load, proving the accuracy of the temperature monitoring system and the calculation method. Finally, one example of the on-site operation and maintenances data is presented to show the actual working condition of the temperature monitoring system.