Stockbridge vibration absorber

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Four Stockbridge vibration absorbers on an overhead line
Stockbridge vibration absorber, detailed view

The Stockbridge vibration damper is a vibration damper for reducing the mechanical vibrations of electrical overhead lines , especially high-voltage lines with long spans between the masts .

Stockbridge vibration absorbers continue to be used to dampen vibrations on the guy ropes of transmission masts and on cable-stayed bridges .

This type of vibration damper was invented in 1928 by George H. Stockbridge , who was an engineer at Southern California Edison at the time.

Cause of the vibrations

A steady, albeit moderate, wind can lead to standing waves with a wavelength of several meters on the conductor between two masts. This is one of the main causes of mechanical damage to the isolators .

To reduce this, especially in long spans, structurally coordinated damper elements are attached, which consist of a short piece of rope with end dimensions. These are clamped to the conductor near the suspension points. Stockbridge vibration absorbers have the shape of a dumbbell that is centrally connected to the conductor cable via a suspension.

Areas of Effect

Stockbridge vibration absorbers on the suspension cables of the Severn Bridge

In overhead lines, wind can lead to mechanical oscillations in the following frequency ranges:

  • the "line gallop" with amplitudes of a few meters and a frequency in the range of 0.08 Hz to 3  Hz .
  • Vibrations due to the aeroelasticity , which has amplitudes in the range of a few millimeters to a few centimeters and is in a frequency range of 3 Hz to 150 Hz.

Stockbridge vibration absorbers act particularly efficiently against vibrations due to the aeroelasticity at a certain frequency determined by the construction. As a result of an asymmetrical mass distribution of the damper elements, good damping properties can also be achieved in different frequency ranges.

Individual evidence

  1. ↑ U.S. Patent No. 1675391, July 3, 1928.
  2. ^ John McCombe, FR Haigh: Overhead Line Practice . 3. Edition. MacDonald, 1966, pp. 216 to 219 .
  3. ↑ EPRI Transmission Line Reference Book: Wind-Induced Conductor Motion . EPRI 1012317, 2008.
  4. ^ Tom Lawson: Building aerodynamics . Imperial College Press, 2001, ISBN 1-86094-187-7 , pp. 115 .