China's deepest submarine cable repair joint passes test in Zhoushan

On March 16, the 525-kilovolt direct current (DC) submarine cable repair joint, developed jointly by State Grid Zhoushan Power Supply Company and a domestic cable manufacturer, completed type testing at a water depth of 900 meters. All performance indicators met the required standards, marking a major breakthrough in China's deep-sea submarine cable emergency repair technology and filling the domestic gap in ultra-deepwater, ultra-high-voltage cable repair equipment.

[Photo provided to chinadaily.com.cn]

This submarine cable connector is China's first 525 kV DC repair joint specifically engineered for ultra-deepwater environments at a depth of 900 meters. Designed for extreme deep-sea conditions including high voltage, complex currents, and severe corrosion, the innovation was developed through joint efforts by State Grid Zhoushan's R&D team and domestic manufacturers. After multiple rounds of technical breakthroughs, the team overcame core challenges such as structural optimization for deep-water applications, ultra-high-pressure sealing processes, and installation compatibility in extreme marine environments.

[Photo provided to chinadaily.com.cn]

State Grid Zhoushan conducted rigorous testing and verification of the cable joint, including hydraulic pressure, mechanical strength, electrical insulation, and long-term aging tests. The joint demonstrated reliable sealing reliability, electrical insulation performance, and mechanical load-bearing capacity in ultra-deepwater environments, meeting engineering application requirements with overall superior performance.

This cable joint can be widely used in deep-sea offshore wind power projects, inter-island power grid connections, and offshore oil and gas development. It enables rapid emergency repairs of submarine cable faults, significantly reduces downtime at deep-sea energy facilities, enhances the operation and maintenance capabilities of China's deep-sea power transmission systems, and provides key technical support for the independent control of marine power transmission equipment and the large-scale development of marine energy resources.