Conductor vibration of transmission line refers to the movement or oscillation of the electrical conductors that make up the transmission line. Various factors, including wind, ice, and mechanical stresses on the transmission line, can cause this.
Conductor vibration can have several negative impacts on transmission lines, including:
Increased power loss: Vibrations can cause the conductors to rub against each other or against the insulators, which can increase the resistance of the transmission line and cause power losses.
Damage to equipment: Vibrations can cause damage to the transmission line and its supporting structures, such as poles or towers, and the electrical equipment connected to the transmission line.
Interference with communication: Vibrations can cause interference with communication systems that use the transmission line for support, such as telecommunications or television cables.
Safety hazards: Vibrations can cause the transmission line to become unstable and potentially collapse, posing a safety hazard to people and property.
To mitigate the effects of conductor vibration, transmission line operators may use various techniques, such as installing damping devices, reinforcing transmission line structures, or using different conductors with lower vibration frequencies.
Types of Mechanical Vibration in Transmission Lines
Following are several types of mechanical vibration that can witness in Electrical Power Lines.
Resonant vibration
Resonant vibration in transmission lines occurs when the natural frequency of the transmission line conductors matches the frequency of an external force, such as wind or ice. This can cause the transmission line conductors to vibrate more severely, leading to increased power loss, damage to equipment, interference with communication systems, and safety hazards. Resonant vibration can be caused by several factors, including:
- The natural frequency of the transmission line is the frequency at which the transmission line conductors naturally vibrate when they are subjected to external forces. The natural frequency of a transmission line depends on several factors, including the mass and stiffness of the conductors and the length and spacing of the conductors.
- The frequency of the external force: This is the frequency at which the transmission line is subjected to an external force, such as wind or ice. If the external force’s frequency matches the transmission line’s natural frequency, resonant vibration can occur.
- The magnitude of the external force: The severity of the resonant vibration will depend on the importance of the external power, as well as the natural frequency and mass of the transmission line conductors.
To prevent or mitigate resonant vibration in transmission lines, operators may use various techniques, such as installing vibration dampers, reinforcing transmission line structures, or using different conductors with lower natural frequencies. It is also necessary to adjust the frequency of the external force to prevent it from resonating with the transmission line.
Galloping
Galloping is a form of oscillation that can happen when strong wind or ice forces push on transmission lines. It is defined by large-amplitude, low-frequency vibrations of the transmission line conductors, which can move the conductors horizontally or vertically.Aerodynamic forces act on a cross-section that isn’t a circle, causing line conductors to vibrate independently. The conductor isn’t a perfect circle because the ice on its exterior isn’t even. This oscillation of conductors with a low frequency and large amplitude is called galloping. People have seen changes with amplitudes of about 11 m and periods of about eight. Galloping conditions don’t happen very often. Galloping has been seen with wind speeds between 15 and 75 km/h and an angle between 10 and 90 degrees to the line. In the conductor, both twisting and multinational motions are set up. It is what makes overhead transmission lines shake. At the attachment points, there may be stresses that aren’t normal, which could damage these same conductors and fittings. Galloping can also cause electrical contact between two conductors or between a phase conductor and the ground. So, the supply could be cut off.
Dancing and sleet-jump
Dancing and sleet-jump are types of oscillation that can occur in transmission lines when subjected to strong wind or ice forces.
Dancing is a type of oscillation characterized by small-amplitude, high-frequency vibrations of the transmission line conductors. It is caused by the wind or ice acting on the conductors, causing them to vibrate rapidly. Dancing can cause power losses and may lead to fatigue and failure of the conductors or insulators.
Sleet-jump is a type of oscillation characterized by large-amplitude, low-frequency vibrations of the transmission line conductors. It is caused by the accumulation of ice on the conductors, which can increase their weight and stiffness. Sleet-jump can cause damage to the transmission line and its supporting structures and the electrical equipment connected to the transmission line. If the transmission line collapses, it can also pose a safety hazard to people and property.
Use of Vibration Dampers in Transmission Lines
Transmission line vibration dampers are devices that reduce or dampen the vibrations of the electrical conductors in transmission lines. They are typically used to prevent the transmission line from becoming unstable or collapsing due to conductor vibrations, which can be caused by factors such as wind, ice, and mechanical stresses on the transmission line.
There are several different types of transmission line vibration dampers, including:
- Helical dampers are spiral-shaped devices attached to the transmission line conductors and designed to absorb energy from the vibrations by deforming elastically.
- Tuned mass dampers: These devices are attached to the transmission line conductors and are designed to absorb energy from the vibrations by moving in the opposite direction to the beats.
- Tension dampers: These devices are attached to the transmission line conductors and are designed to absorb energy from the vibrations by applying a tension force to the conductors.
- Friction dampers: These devices are attached to the transmission line conductors and are designed to absorb energy from the vibrations by creating a friction force between the conductors and the dampers.
Vibration of Transmission Line dampers are essential for mitigating the adverse effects of conductor vibrations on transmission lines. They are typically used with other measures, such as reinforcing transmission line structures or using different types of conductors with lower vibration frequencies.