Dynamic Power Cable Moisture Detection Without Barrier Bulging
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Solution Overview
Problem
Existing moisture ingress detection devices for submarine power cables are not suitable for dynamic power cables due to their inability to be effectively arranged in the tight, compressed space between a water barrier layer and an underlying layer, and they may cause bulging of the water barrier layer, compromising its structural integrity.
Innovation Solution
A moisture ingress detection device comprising an elongated optical fiber surrounded by a water-swellable material, arranged in direct contact with the water barrier layer, without an external rigid sheath, to avoid bulging and ensure structural integrity. The device relies on the tightness of the water barrier layer's wrapping to direct pressure inward towards the optical fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rigid cylindrical sheath is used to direct pressure inward towards the optical fiber, then the moisture detection function is improved, but the water barrier layer bulges and structural integrity is compromised
Solution Approach 1:
The rigid cylindrical sheath is completely removed from the detection device. Instead, the patent uses the water barrier layer's own tight wrapping and compression to provide the necessary pressure direction, extracting the harmful rigid sheath while maintaining the pressure-directed function through the cable's existing structural compression.
Solution Approach 2:
The patent introduces a compliant intermediary layer or uses the naturally compressed space between the water barrier layer and intermediate layer as a mediator. This compliant structure transmits pressure inward toward the optical fiber without causing bulging, replacing the rigid sheath's pressure-directing function with a flexible mechanism.
2Strength
If the detection device is arranged in interstices further to the interior of the cable, then the structural integrity is maintained, but the detection sensitivity and speed are reduced
Solution Approach 1:
The detection device is pre-positioned in direct contact with the water barrier layer during cable assembly, before the cable is put into service. This preliminary placement ensures immediate detection capability without requiring the device to be positioned deep within the cable interior, achieving both sensitivity and structural integrity.
3Measurement precision
If the detection device is placed in direct contact with the water barrier layer, then the detection sensitivity is optimized, but the water barrier layer may bulge and lose structural integrity
Solution Approach 1:
The detection device uses a flexible, compliant housing or wrapping instead of a rigid structure. This flexible shell allows the device to be in direct contact with the water barrier layer for sensitive detection while conforming to the layer's shape and not causing bulging, maintaining structural integrity through flexibility.
4Stress or pressure
If a rigid sheath is used to contain the swellable material, then the pressure direction is controlled, but the device cannot be arranged in the tight compressed space of dynamic cables
Solution Approach 1:
The patent changes the mechanical parameters of the device housing from rigid to flexible or compliant. This parameter change allows the device to adapt to the tight compressed space between the water barrier layer and intermediate layer in dynamic cables, while still maintaining pressure direction control through the compression provided by the cable's own structure.
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 allows for quick and precise detection of moisture ingress in dynamic submarine power cables, optimizing sensitivity by being in direct contact with the water barrier layer while maintaining the structural integrity of the cable.
Implementation Method 1
an elongated optical fiber surrounded by a water-swellable material, the swellable material arranged to expand upon contact with moisture
Implementation Method 2
exert a pressure on the underlying optical fiber sufficient to cause an observable change in the attenuation and/or propagation characteristics of the optical fiber
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A
AI summary
A power cable arrangement (28,40) , having a power core with one or more conductors, an intermediate layer disposed about the power core, a water barrier layer tightly arranged about the intermediate layer, and a moisture ingress detection device (10,29) arranged between the water barrier layer and the intermediate layer in direct contact with the water barrier layer. The moisture ingress detection device comprising an elongated optical fiber (12) surrounded by a water-swellable material (14,32) , the swellable material arranged to expand upon contact with moisture and exert a pressure on the underlying optical fiber sufficient to cause an observable change in the attenuation and/or propagation characteristics of the optical fiber.