Pre-stressed Conductors with Reduced Thermal Knee Points
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Solution Overview
Problem
Conventional electrical conductors for transmission and distribution face challenges such as high thermal knee points, leading to increased sag and limited current carrying capacity, especially in high-temperature and ice-heavy environments, due to conductive materials being under tensile stress, and require costly pre-stressing and specialized installation procedures.
Innovation Solution
The development of electrical conductors with pre-tensioned composite strength members, where the strength members are under tensile stress and the conductive materials are mostly tension-free or under compression, achieved through encapsulation with conductive materials like aluminum or copper, allowing for reduced thermal knee points without the need for on-site pre-stressing, thus enhancing installation ease and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional conductors with conductive materials under tensile stress are used, then the conductor can be easily manufactured and installed, but the thermal knee point is high resulting in increased thermal sag and limited current carrying capacity
Solution Approach 1:
The strength member is pre-stressed during manufacturing to establish a residual tensile stress state before the conductor is installed. This preliminary action ensures that when the conductor is installed in the conventional manner (without complex pre-stressing procedures), the conductive materials remain compression-free, thereby reducing the thermal knee point and minimizing thermal sag throughout the conductor's operational life.
2Temperature
If Gap conductor with suppressed thermal knee point is used, then thermal sag is reduced, but the installation process becomes complex requiring special procedures, extended time, and additional labor
Solution Approach 1:
The complex pre-stressing operation is performed in advance during the conductor manufacturing process, not during field installation. The strength member is pre-stressed to the required level before the conductor is shipped to the installation site. This transfers the time-consuming operation from the installation phase to the manufacturing phase, allowing conventional quick installation methods to be used in the field.
Solution Approach 2:
The conductor is designed to be self-pre-stressed through its construction methodology. The pre-stressed strength member automatically provides the necessary compression to the conductive materials without requiring external pre-stressing equipment or special installation procedures. The conductor essentially installs itself in the optimal stress state using conventional installation practices.
3Temperature
If pre-stress conditioning is applied to reduce thermal knee point, then thermal sag is reduced, but the conductor requires costly specialized installation procedures and equipment
Solution Approach 1:
All complex pre-stressing operations are completed during manufacturing using factory equipment. The conductor arrives at the installation site already conditioned with the desired stress state, eliminating the need for specialized field pre-stressing equipment and procedures. Standard installation tools and methods suffice.
Solution Approach 2:
The conductor structure itself provides the pre-stressing function through its design. The pre-stressed strength member inherently maintains the conductive materials in a compression-free state without requiring external active systems or complex installation procedures. The conductor is self-sufficient in maintaining its optimal thermal performance.
4Device complexity
If conductive materials are under tensile stress in conventional conductors, then the conductor structure is simple, but the thermal expansion is high resulting in large sag and limited current carrying capacity
Solution Approach 1:
The conductor structure is designed with differentiated stress states for its different components. The strength member is specifically engineered to carry tensile stress and provide pre-stress, while the conductive materials are positioned and dimensioned to remain compression-free or under minimal tension. This local differentiation of stress roles allows the conductive materials to exhibit minimal thermal expansion without compromising the overall structural integrity of the conductor.
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 results in conductors with significantly reduced thermal sag, increased capacity, and improved energy efficiency, while being cost-effective, easy to install and maintain, and less sensitive to temperature variations, effectively managing ice and wind loads without compromising conductor integrity.
Implementation Method 1
the strength members are under tensile stress and the conductive materials are mostly tension-free or under compression
Implementation Method 2
the conductor thermal expansion is substantially controlled by conductive material such as aluminum or copper with high thermal expansion coefficient
Data Source
AI summary
The present invention relates to electrical conductors for electrical transmission and distribution with pre-stress conditioning of the strength member so that the conductive materials of aluminum, aluminum alloys, copper, copper alloys, or copper micro-alloys are mostly tension free or under compressive stress in the conductor, while the strength member is under tensile stress prior to conductor stringing, resulting in a lower thermal knee point in the conductor.