Recently, the 550kV DC submarine cable, jointly developed by State Grid and several domestic companies, completed its laying test in the Zhoushan sea area. The cable utilizes new cross-linked polyethylene insulation material and lead alloy sheathing, overcoming challenges related to deep-sea high-voltage insulation and mechanical protection. Its power transmission capacity has increased by 40% compared to the previous generation. This breakthrough will be directly applied in China's first integrated "Deep-sea Wind Power - Island Microgrid" project, marking China's transition from "following" to "leading" in the field of ultra-high-voltage submarine cables.