Subsea Cable Motion Detection via TDR Impedance
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Solution Overview
Problem
Subsea power cables are prone to failure due to forces from the sea, such as tides and vortices, which cause motion leading to degradation and failure of conductors and insulators, making it difficult to locate and costly to repair.
Innovation Solution
The method involves using time-domain reflectometry (TDR) to detect motion in electrical cables by sending a TDR signal along each core of the cable, receiving reflections, generating reflectometry data, and comparing it with reference data to identify impedance changes indicative of cable motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-domain reflectometry is used to detect cable motion, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces mechanical monitoring systems with electromagnetic field-based time-domain reflectometry to detect cable motion. By using TDR signals to measure impedance changes caused by motion, the system achieves high measurement precision without complex mechanical sensors or actuators along the cable route.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using impedance changes as a mediator to detect cable motion. Instead of directly measuring physical displacement, the system measures electrical impedance variations that result from motion, simplifying the detection mechanism while maintaining precision.
2Reliability
If long-term monitoring is implemented to prevent cable failure, then reliability is improved, but loss of time increases
Solution Approach 1:
The patent implements preliminary monitoring to detect cable motion and potential failures before they occur. By continuously measuring impedance changes and comparing them against baseline data, the system identifies early signs of cable stress or damage, enabling preventive maintenance scheduling that avoids both failures and unnecessary maintenance interruptions.
Solution Approach 2:
The patent establishes a feedback mechanism by comparing real-time TDR measurements with reference baseline data. This feedback loop allows the system to automatically identify deviations indicating cable motion or degradation, triggering alerts that enable timely preventive maintenance without requiring continuous manual inspection or causing unnecessary maintenance events.
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
This approach allows for the detection of cable motion that may lead to failure, enabling preventative maintenance and reducing the risk of costly repairs and power disruptions.
Implementation Method 1
sending a time-domain reflectometry (TDR) signal from a point of measurement along each core of the cable; receiving, at the point of measurement, one or more reflections of the TDR signal from each core
Implementation Method 2
motion of the cable causes a measurable change in the impedance of the cable's cores
Data Source
AI summary
A method (900) of detecting motion of an electrical cable comprising at least one core comprises sending (S91) a time-domain reflectometry, TDR, signal from a point of measurement along each core of the cable. Reflections of the TDR signal from each core are received (S92) at the measurement point, and a reflectogram is generated (S93) for each core by correlating the TDR signal with the reflections. Each reflectogram is a waveform of relative impedance change against distance from the point of measurement. Motion of the cable is detected by comparing (S94) the reflectogram generated for each core with a reference reflectogram for the respective core, where each reference reflectogram was previously obtained when the cable was in a baseline position.