A high-voltage electrical power supply line for the provides a secure and water-proof connection transfer of high-voltage electricity through an inner high-voltage electrical cable between a single point mooring (SPM) buoy and/or a caternary anchor leg mooring (CALM) buoy and an LNG vessel moored to the SPM CALM buoy, with a secured connection on each end of the high-voltage electrical cable, disallowing and prevent current flow through high-voltage electrical cable until a secure and confirmed connection is established between connectors attaching the high-voltage electrical power supply line to the SPM CALM buoy and the LNG vessel.

A floating power-generation group comprises a floating hub such as a spar buoy that is anchored to subsea foundations by anchor lines. Floating power producer units such as wind turbines are connected electrically and mechanically to the hub. The power producer units are each moored by mooring lines. At least one mooring line extends inwardly toward the hub to effect mechanical connection to the hub and at least one other mooring line extends outwardly toward a subsea foundation. The groups are combined as a set whose hubs are connected electrically to each other via subsea energy storage units. Anchor lines of different groups can share subsea foundations. The storage units comprise pumping machinery to expel water from an elongate storage volume and generating machinery to generate electricity from a flow of water entering the storage volume. The pumping machinery can be in deeper water than the generating machinery.

A method for holding a cable in a wind turbine transition piece by a cable hang-off device, the method includes providing a cable hang-off device comprising a main body with a first flange, an opposed second flange and a through passage, a sealing sleeve with a sealing passage, at least one temporary clamp, located in the through passage, a clamping plate, and at least one solid sealing element, attaching the main body to the wind turbine transition piece with the first flange, attaching the sealing sleeve to the second flange, inserting the cable through the through passage and the sealing passage sleeve, clamping an outer serving of the cable with the at least one temporary clamp, pealing the outer serving of the cable to reveal armour wires of the cable, folding the armour wires over the second flange in a radially outward direction, with respect to a longitudinal direction of the cable hang-off device, inserting the clamping plate in the sealing passage, clamping the armour wires against the second flange, by the clamping plate, releasing the at least one temporary clamp from outside the main body to release a clamping force from the at least one temporary clamp, inserting the at least one solid sealing element in the sealing passage to at least partially surround one or more conductors of the cable, and sealing the sealing passage with the at least one solid sealing element.

A system for transmission of power offshore comprises two or more power stations operably connected with a high voltage cable system. The high voltage cable system may comprise a dynamic, dry or wet type high voltage submarine cable of varying length configured to transmit at least about 100 megawatts of power. In some cases the dynamic, dry or wet type high voltage submarine cable comprises a first end connected to an offshore power station and second end connected to a static submarine cable system which is connected to an onshore power station. The systems may facilitate transmission of power for applications such as compressing and/or pumping subsea natural gas in deep water.

A system for transmission of power offshore comprises two or more power stations operably connected with a high voltage cable system. The high voltage cable system may comprise a dynamic, dry or wet type high voltage submarine cable of varying length configured to transmit at least about 100 megawatts of power. In some cases the dynamic, dry or wet type high voltage submarine cable comprises a first end connected to an offshore power station and second end connected to a static submarine cable system which is connected to an onshore power station. The systems may facilitate transmission of power for applications such as compressing and/or pumping subsea natural gas in deep water.