Wind Turbine Power Cable Torsional Resistance Design

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Solution Overview

Problem

Power cables used in wind mill power plants experience premature breakage due to alternate torsional stresses, leading to frequent maintenance and reduced service life, as the outer jacket's non-constant thickness and penetration into interstitial areas restrict earth conductor movement, causing stress concentrations and breakage.

Innovation Solution

A power cable design with a tubular outer jacket of constant thickness, allowing earth conductors to move radially and circumferentially, reducing stress concentrations and enhancing resistance to torsional stresses, while maintaining a compact structure and easy manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the outer jacket penetrates into the interstitial areas between earth conductors and power conductors (non-constant thickness), then the cable structure is more compact, but the earth conductors are constrained and subjected to stress concentrations causing premature breakage

Engineering Contradiction:

Improvecable structure compactnessVSAvoidearth conductor resistance to torsional stress

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The outer jacket is designed with different functional zones: in the interstitial areas, it maintains constant thickness and does not penetrate between conductors, allowing earth conductors to move freely; at the power conductors extrados, it provides normal protection. This local differentiation resolves the contradiction by allowing compactness where needed while preventing stress concentration on earth conductors.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of allowing the outer jacket to penetrate into interstitial areas (conventional design), the invention inverts this approach by keeping the jacket away from interstitial areas with constant thickness, thereby freeing the earth conductors from constraints while maintaining overall cable compactness through alternative structural arrangements.

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If the outer jacket has non-constant thickness penetrating into interstitial areas, then the cable assembly is more compact, but the earth conductors experience constrained movement and stress concentration leading to breakage

Engineering Contradiction:

Improvecable assembly compactnessVSAvoidearth conductor strength under torsional stress

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The outer jacket applies protection locally at the power conductors extrados while maintaining constant thickness and avoiding penetration into interstitial areas, thereby preserving earth conductor strength and freedom of movement while maintaining overall cable compactness through this differentiated local approach.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The cable structure is segmented into distinct functional zones: power conductors with their extrados protected by the outer jacket, and interstitial areas left free of jacket penetration to allow earth conductor movement. This segmentation resolves the contradiction by separating the protection function from the constraint function.

Inventive Principle:

Principle #1Segmentation

3Volume of moving object

If the outer jacket penetrates into interstitial areas with variable thickness, then the cable structure is optimized for compactness, but the earth conductors are restricted in movement causing premature breakage under alternate torsional stresses

Engineering Contradiction:

Improvecable volume efficiencyVSAvoidcable service life

Core Design Contradiction:

Volume of moving objectVSDuration of action of stationary object

Solution Approach 1:

The outer jacket is designed with local quality differentiation, maintaining constant thickness and avoiding interstitial area penetration to ensure earth conductor freedom of movement throughout the cable service life, while achieving volume efficiency through optimized overall cable geometry and conductor arrangement.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention inverts the conventional approach by keeping the outer jacket away from interstitial areas with constant thickness, thereby ensuring long-term durability and freedom of earth conductor movement, while achieving compactness through alternative structural optimizations.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8669474B2Power cable with high torsional resistance

Publication Date: 2014.03.11 PRYSMIAN CABLES & SISTEMAS SL

AI summary

A power cable includes at least two power conductors, at least one earth conductor, and a tubular outer jacket surrounding the power conductors and earth conductor. Each power conductor may comprise a conductive core and an insulating layer surrounding said conductive core. The power conductors may be twisted and contact each other. The earth conductor may have a diameter smaller than the power conductors and may be positioned in the interstitial area between two adjacent power conductors and the outer jacket. The earth conductor may contact the two power conductors along two respective contact lines and the outer jacket along an extrados portion facing outward with respect to the cable. The outer jacket may have substantially constant thickness. The lateral surfaces of the earth conductor may be free from constraints between the contact lines with the power conductors and the extrados contacted by the outer jacket.