Coaxial Power Cable for Direct Electric Heating
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Solution Overview
Problem
Existing subsea electric power cables face challenges in dynamic applications due to excessive electric losses and corrosion issues when used for direct electric heating of oil or condensate pipelines, particularly when subjected to expansion and contraction, and the formation of hydrates or wax plugs that impede pipeline flow.
Innovation Solution
A coaxial dynamic riser and feeder cable design with two conductors and a concentric conductor adapter that minimizes electromagnetic induction and corrosion, featuring a central conductor connected via a piggyback cable and a concentric conductor connected to the pipeline, with a terminal assembly using cones and press-plates for secure and corrosion-resistant connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal armoring is applied to the cable to provide sufficient protection against squeezing and stretching forces, then mechanical strength and protection are improved, but excessive electric losses occur due to electromagnetic induction in the metal armoring
Solution Approach 1:
The patent removes the metal armoring from the cable structure entirely, replacing it with a non-conductive polymer sheath. This extraction eliminates the source of electromagnetic induction losses while maintaining mechanical protection through the flexible polymer material that can withstand squeezing and stretching forces during pipeline operations.
Solution Approach 2:
The patent changes the material parameter of the outer protective layer from conductive metal to non-conductive polymer. This parameter change transforms the cable from having electromagnetic induction capabilities to being electrically isolated, thereby eliminating energy losses while preserving mechanical integrity through the polymer's inherent strength and flexibility.
2Device complexity
If a single-core cable is used for direct electric heating, then the cable structure is simplified and installation is easier, but the cable lacks sufficient protection against squeezing and stretching forces during dynamic operations
Solution Approach 1:
The patent employs a composite cable structure consisting of a central conductor, insulation layer, and an outer protective polymer sheath. This composite design maintains the simplicity of a single-core configuration while the multi-layer composite structure provides enhanced mechanical protection against squeezing and stretching forces during pipeline expansion and contraction.
3Ease of operation
If a three-core dynamic cable is used to improve bending properties, then dynamic properties are improved, but dimensions, weight and cost increase significantly
Solution Approach 1:
The patent designs a single-core cable with a flexible polymer sheath that dynamically adapts to bending and stretching forces. The polymer material's inherent flexibility allows the cable to accommodate pipeline movements and bending without requiring additional cores, thereby maintaining good dynamic properties while minimizing weight and dimensions.
4Productivity
If alternating current is used for heating the pipeline, then heating efficiency is improved, but excessive electric losses occur when metal armoring is present due to electromagnetic induction
Solution Approach 1:
The patent removes the metal armoring that causes electromagnetic induction losses, allowing alternating current to be used for efficient pipeline heating without the harmful side effect of energy loss in the armoring. The extraction of this problematic component enables the full benefits of AC heating to be realized.
Solution Approach 2:
The patent creates an electrically inert environment by surrounding the conductor with a non-conductive polymer sheath instead of metal armoring. This inert electromagnetic environment allows alternating current to flow through the conductor for heating purposes without inducing parasitic currents in the cable structure, thereby maximizing heating efficiency while minimizing energy losses.
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 coaxial cable design enhances dynamic and electromagnetic properties, reducing power losses and preventing corrosion, while the terminal assembly ensures reliable and cost-effective connections, addressing the inefficiencies and operational risks of previous systems.
Implementation Method 1
The direct heating system is based on the fact that an electric current in a metal conductor generates heat due to ohmic loss
Implementation Method 2
at least one cone (conically shaped metallic ring) is adapted to squeeze the concentric conductor of the electric power cable against an electric conductive part of the concentric conductor adapter
Data Source
AI summary
Electric power cable used as a riser (15) and/or feeder cable (16) in a Direct Electric Heating system for oil or condensate pipelines (10), comprising at least two conductors (1, 5) and insulation layers (3, 6). An outer concentric conductor (5) is connected to a near end of the pipeline, and a central conductor (1) is connected via a piggyback cable (12) to a far end of the pipeline, to provide power for the heating. Another aspect is a terminal assembly adapted to providing an electric connection of the electric power cable with the pipeline (10), where a cone (41) is adapted to squeeze the concentric conductor (5) against a concentric conductor adapter (40).