How Vibration Damper Works in Transmission Line?

How Does a Small Size Damper Reduce Vibration in Transmission Lines?

Vibration dampers are usually used in high voltage and extra-high voltage electrical energy overhead transmission lines to handle aeolian and galloping or dancing vibrations in the transmission lines' conductors. The dampers are designed in such a way that they attenuate the line vibrations by reaching the same frequency as the cable that has wind-induced vibrations.

The overhead Transmission Line mainly experiences two types of vibrations in a vertical plane which can be categorized into two groups.

• Aeolian Vibration;
• Galloping or Dancing vibration.

Aeolian Vibration has a high frequency and low amplitude at shallow velocity (4 to 15 km/hr) of wind, like- a vibration frequency of 5 to 40 cycles/second, and the amplitude is 2 cm to 5 cm with a loop length of 1 m to 10 m. 

Galloping or Dancing Vibration is having self-explanted type of a low frequency but higher amplitude, like- 1/4 – 3/2 cycle/second, and an amplitude of vibration around 10 m.

The Vibration phenomenon in the Transmission Line is solved by using specially designed dampers called Stockbridge Damper which is basically a device to absorb vibration energy and prevent vibration in the Transmission Line.

Stockbridge Damper

The Stockbridge damper was invented in the 1920s by engineer George H. Stockbridge, as per his name it is called Stockbridge. In early Stockbridge dampers used concrete as damper mass material, nowadays it uses some heavy metal.

As in the figure's right end, the Stockbridge Damper has two masses at the ends of a connecting rod or stiff cable which gives it a dumbbell shape. It is connected to the line conductor immediately above it through a clamp. They can effectively dampen Aeolian wind vibrations.

See video of what actually happens during conductor vibration

Stockbridge Dampers absorb vibrational energy and thus prevent the formation of standing waves which can cause serious stress fatigue to the energy transmission line and damage it. 

The Spiral Vibration Damper

Smaller diameter  (less than 0.75") conductors like shield wire or optical ground wire (OPGW), a Stockbridge damper is not suitable rather a different type and more effective damper is available named Spiral Vibration Damper. 

The Spiral Vibration Damper has been used successfully over the last few decades to control Aeolian Vibration on these smaller sizes of overhead transmission line conductors and wires.

Spiral Vibration Damper

Spiral vibration dampers have a helically-formed damping section sized for the interplay of damper and cable to provide the action/reaction motion such that they impact during Aeolian vibration activity that absorbs the natural vibration wave.