Vibration in overhead conductors is a very serious issue. Excessive vibration can result in conductor failure which can be catastrophic. Vibrations should be kept within limits for safe operation of the transmission lines.
Vibration in Power Lines can be categorized into three types.
- Aeolian Vibration
- Gallop
- Simple swinging
Aeolian Vibration
These vibrations are caused by aerodynamic forces generated as the wind blows across the conductor. The frequency of the vibration may receive a positive feedback from the conductor's natural vibration frequency. This self-exciting vibration can cause cracks on the conductors due to fatigue and can cause damage particularly where the conductors is fastened to the insulators by means of clamps
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| Dampers on conductors near the string insulator |
This kind of vibration can be minimized by the use of dampers. The most widely used damper is the stock bridge damper. This damper consists of two weights which are fitted on either side of a cable. This shape is known as a "dog bone". The cable is fastened to the main conductor by means of clamps.
When the conductor vibrates, the weights fitted on either side vibrate and dissipate the vibrational energy.
Gallop
These vibrations are low frequency and high amplitudes. These vibrations are caused by the wind blowing over conductors which are not circular . Hence, conductors are designed to be circular to prevent gallop-type vibrations. These vibrations can result in breaking of the conductor. They can also result in flash over if the conductors come too close to each other during oscillations.
Simple Swinging
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| Stockbridge Vibration Damper |
This kind of vibration occurs in the horizontal direction as the conductors swing under the influence of wind. This kind of swinging does not have any major impact. However, it needs to be ensured that the that lines to not come too close to each other or the tower to cause a flash over.