Dynamic Subsea Cable Sheath Pressure Balancing
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Solution Overview
Problem
Existing dynamic subsea cables are unable to withstand hydrostatic pressures at depths greater than 400-600 meters due to damage from substantial mechanical stress and fatigue, limiting their operational depth and longevity.
Innovation Solution
Incorporating a corrugated metal sheath with a dielectric liquid between the electrical insulation system and the corrugated sheath to counteract deformation from hydrostatic pressure, allowing the cable to maintain mechanical strength and withstand higher pressures, enabling operation up to several thousand meters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a corrugated metal sheath is used to protect against radial water penetration, then the cable's resistance to mechanical stress and fatigue is improved, but the cable cannot withstand hydrostatic pressure at depths greater than 400-600 meters
Solution Approach 1:
A liquid medium is introduced as an intermediary substance between the electrical insulation system and the corrugated metal sheath. This liquid transmits hydrostatic pressure uniformly to the sheath, preventing deformation and water penetration while maintaining the protective function of the corrugated structure. The liquid acts as a pressure-distributing mediator that enables deep-sea operation.
Solution Approach 2:
The invention utilizes hydraulic pressure transmission through a liquid medium to counteract external hydrostatic pressure. The liquid-filled space between the insulation system and corrugated sheath creates a hydraulic support system that maintains structural integrity at great depths, applying internal pressure that balances the external water pressure.
2Ease of manufacture
If the cable is designed for shallow depths (400-600 meters), then the corrugated sheath structure is simpler and easier to manufacture, but the operational depth is limited
Solution Approach 1:
The corrugated metal sheath serves multiple functions: it provides mechanical protection against stress and fatigue, acts as a radial water barrier, and serves as a pressure-receiving surface for the liquid medium. This multi-functional design enables the same structure to operate effectively across a wide depth range without requiring fundamental design changes.
Solution Approach 2:
The invention changes the operational parameters of the corrugated sheath by introducing a liquid medium that adapts to varying hydrostatic pressures. The liquid pressure transmission system allows the rigid corrugated structure to function dynamically at different depths, transforming the cable from a shallow-water design to a deep-sea capable system.
3Stress or pressure
If a liquid is introduced between the electrical insulation system and the corrugated sheath, then the cable can withstand higher hydrostatic pressure, but the device complexity increases
Solution Approach 1:
The liquid-filled space is nested within the existing cable structure, between the electrical insulation system and the corrugated metal sheath. This nested configuration utilizes the existing annular space without requiring additional external components, thereby minimizing structural complexity while achieving the pressure-withstand function.
Solution Approach 2:
The liquid medium automatically adjusts to external hydrostatic pressure without requiring active control systems. The liquid self-regulates the internal pressure distribution, eliminating the need for pumps, valves, or control mechanisms. The system serves itself by using the physical properties of the liquid to maintain structural integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables dynamic high voltage subsea cables to operate at greater depths while maintaining mechanical strength and preventing moisture penetration, thus extending the cable's lifespan and operational range.
Implementation Method 1
the liquid creates a pressure in the annular channel towards the internal surface of the corrugated sheath which varies with the depth of the dynamic high voltage subsea cable. In the top of the cable, there will be an atmospheric pressure, and at depth the pressure is given by the density of the liquid, times the depth, times the gravitational acceleration. This pressure will therefore be of the same order of magnitude as the hydrostatic pressure applied to the corrugated sheath.
Data Source
Figure 1~2b
Figure 3
AI summary
The present disclosure relates to an arrangement (5) for a dynamic high voltage subsea cable comprising an electrically conductive core (13), a corrugated sheath (9) defining a radial water barrier, an electrical insulation system (11) arranged to insulate the electrically conductive core (13) from the corrugated sheath (9), and a liquid (17). The electrical insulation system (11) has an external surface (11a) and the corrugated sheath (9) has an internal surface (9b), and wherein the liquid (17) is arranged between the external surface (11a) of the electrical insulation system (11) and the internal surface (9b) of the corrugated sheath (9) for counteracting deformation of the corrugated sheath (9).