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Havard Engineering Inc. - Conductor Vibration Monitoring
Havard Engineering Inc.
Conductor Vibration Monitoring
Overhead conductors vibrate due to the action of wind on their circular cross-section. Vortices are shed alternately from the top and bottom of the downstream surface of the conductor, causing the conductor to vibrate in the vertical plane. This vibration is conventionally controlled within safe limits of motion by the use of dampers on the conductors or structural supports at the suspension clamps. These vibration effects can occur on single conductors and on all configurations of bundle conductors.
A vibration recorder monitoring conductor motions at an AGS clamp on an operating line is shown on the left.
Sometimes the vibration becomes excessive, usually due to inadequate or improperly located dampers, and the conductor suffers damage from wear and fatigue at the suspension clamps, or the dampers suffer damage to overworking. To evaluate the effectiveness of the damping system, the vibration of the actual conductors is monitored using vibration recorders. Based on the amplitude, frequency and number of cycles of the vibration, the safety of the conductor can be assessed. Such field measurements permit the damping system to be evaluated and, if required, modified to ensure that the conductor does not suffer further damage.
A specially designed asymmetric mounting arrangement to optimize Stockbridge damper effectiveness is shown on the right.
Occasionally, the damping from the Stockbridge dampers, or the stress distribution from cushioned suspension clamp supports, can be sufficient to protect the conductor, but some vibration can be transmitted to the towers. This vibration can cause damage to insulators strings, suspension hardware and tower arm members.
The photo on the left shows U-bolts from suspension hardware with grooves due to wear from conductor vibration after sixty years of service.
If you have concerns regarding vibration on your overhead conductors, let us help you assess the situation. Our experience with this type of problem enables us to provide an effective service to utilities at reasonable cost. Just send us an e-mail and we will contact you promptly to discuss your problem and suggest a practical approach to achieving a solution.
Updated October 9, 2006
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