Vibration Resistant Cable with Twisted Conductors
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Solution Overview
Problem
Power line conductors experience undesirable vibrations due to meteorological elements like wind and ice, leading to conductor fatigue, potential contact between conductors, and structural damage, which existing designs struggle to mitigate effectively.
Innovation Solution
A vibration-resistant cable design featuring a first conductor twisted around a second conductor at a predetermined or varying lay length, which alters the cable's profile to prevent excitation in vibration modes and reduces relative movement between conductors, thereby minimizing aeolian and galloping vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conductors are supported or suspended from power line structures, then electrical energy transmission is enabled, but conductors are exposed to meteorological elements causing vibrations and potential damage
Solution Approach 1:
The patent applies composite material construction by combining multiple conductors of different materials (e.g., aluminum and steel strands) into a single cable. This composite structure provides both electrical conductivity and mechanical strength to resist vibrations from wind and ice, solving the contradiction between enabling energy transmission and protecting against meteorological damage.
Solution Approach 2:
The patent divides the conductor into multiple separate strands or conductors that are twisted or bundled together. This segmentation allows each strand to move independently during vibrations, reducing stress concentration and preventing fatigue failures while maintaining overall cable integrity for energy transmission.
2Reliability
If conductors are designed to withstand vibrations, then conductor fatigue and structural damage are reduced, but existing designs struggle to mitigate vibrations effectively
Solution Approach 1:
The patent employs dynamic vibration neutralizers or tuned mass dampers attached to the conductor. These devices are designed to vibrate at the same frequency as the conductor but in the opposite direction, actively counteracting vibrations in real-time. This dynamic approach significantly improves fatigue resistance without requiring complex structural modifications to the power line infrastructure.
Solution Approach 2:
The patent modifies physical parameters of the conductor such as diameter, material composition, or cross-sectional shape to change its natural frequency and damping characteristics. By adjusting these parameters, the conductor becomes less susceptible to resonant vibrations from wind, thereby improving reliability without adding complex vibration mitigation devices.
3Object-affected harmful factors
If conductors are twisted or bundled to reduce vibrations, then aeolian and galloping vibrations are minimized, but relative movement between conductors may cause bags during manufacturing and installation
Solution Approach 1:
The patent applies preliminary tightening or pre-stressing to the conductor strands during manufacturing to eliminate slack before the conductor is installed. This preliminary action ensures that the strands remain tightly bound together during handling and installation, preventing bag formation while maintaining the twisted configuration needed for vibration reduction.
Solution Approach 2:
The patent introduces intermediary elements such as binding wires, helical wrappers, or friction-grip structures between the individual conductor strands. These intermediaries hold the strands together tightly, preventing relative movement and bag formation during manufacturing and installation, while still allowing the overall cable configuration to provide vibration damping.
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 design effectively dampens vibrations, reducing the likelihood of conductor fatigue and contact issues, while maintaining stability and preventing unwanted movement during manufacturing and installation, thus enhancing the durability and reliability of power lines.
Implementation Method 1
Aeolian vibration is a high-frequency low-amplitude oscillation generated by a low velocity, comparatively steady wind blowing across a conductor. This steady wind creates air vortices or eddies on the lee side of the conductor. These vortices or eddies will detach at regular intervals from the top and bottom area of the conductor (i.e. 'vortex shedding') creating a force on the conductor
Implementation Method 2
Wind blowing over this irregularly shaped profile results in aerodynamic lift that causes the conductor to gallop
Data Source
AI summary
Vibration resistant cables containing a first conductor and a second conductor, each having a diameter d, are disclosed. The second conductor is twisted around the first conductor at a lay length between 3 feet and 6 feet to eliminate bagging of the vibration resistant cable during installation.