The State Grid Zhoushan Power Supply Company recently conducted its first integrated air-surface-underwater inspection of intertidal submarine cables in Zhejiang, a mission that deployed a self-developed twin-hulled unmanned vessel, an aeromagnetic drone and an underwater patrol robot, marking a major step toward fully intelligent all-scenario maintenance.

Serving as the power lifeline, Zhoushan's submarine cables stretch over 1,000 kilometers, with many segments lying in intertidal shallows where ships cannot enter, crews cannot operate, and instruments often fail, creating conditions that have long complicated maintenance. The twin-hulled unmanned vessel used in this operation was designed to overcome these persistent bottlenecks.

The vessel, domestically developed, measures 7 meters in length and 3 meters in beam, with a draft of only 0.5 meters. Its twin-hull configuration gives it a unique grounding capability, enabling it to operate in shallow restricted zones that conventional vessels cannot access.

More noteworthy is its pioneering forward-detection mode, which provides full 360-degree coverage across the bow, hull bottom, sides, and stern. Combined with its bow thruster and operational A-frame, the vessel can flexibly carry out a range of tasks, including subsea cable route detection and condition monitoring.

During the inspection, an integrated air-surface-underwater system was unfolded. A drone equipped with a high-precision magnetometer used an acoustic-optical-magnetic fusion algorithm to map the seabed and transmit real-time data on cable depth and location. On the surface, the twin-hulled unmanned vessel worked with the mother ship to record cable conditions. Underwater, a patrol robot examined the cables for sheath wear, displacement and other potential issues, identifying risk areas with precision.

"A survey that once required a three-day manual team can now be completed in just half a day using the air-surface-underwater collaborative system," said a subsea cable maintenance technician at State Grid Zhoushan Power Supply Company.

The system uses 5G and satellite links for uninterrupted data transmission, lifting inspection efficiency by over 80 percent, cutting operating costs by 60 percent, and virtually eliminating safety risks for on-site personnel, he added.