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Havard Engineering Inc. - Conductor Galloping Control
Havard Engineering Inc.
Conductor Galloping Control
Single and bundle conductors of overhead lines gallop when moderate winds blow across conductors after ice has deposited on them. The motions can be violent, with conductors moving with up to 30 feet peak to peak amplitude, with the motion mainly in the vertical plane. Simultaneously, large dynamic forces are applied to the structures. Often adjacent phases clash together causing power outages, and the conductors, supporting hardware and structures suffer mechanical damage. The contacts between conductors can be minimized by use of large spacings between phases at the tower, or by interphase spacers. These measures do not reduce the dynamic forces, but do reduce the disruptions of the power system.
Interphase spacers and detuning pendulums installed on a two-conductor bundle line for galloping control are shown on the left above.
At the right is a photo of a design of detuning pendulum for a single conductor transmission line.
As a result of extensive laboratory research and field evaluations on operating utility power lines, a method of control of galloping single and bundle conductors has been developed. The control device is the detuning pendulum which is designed to interfere with the synchronous vertical and torsional motions which are characteristic of observed galloping motions. These pendulums are designed to suit the mechanical properties of the conductor, the span length, and the conductor tension, and for bundles, the number of subconductors and their spacing.
Pendulums are masses suspended below the conductor or conductor bundle at several locations across the span. The number of masses and the pendulum arm length required depend mainly on the conductor size and span length. The number of pendulums has been established based on twenty years of field experience. The pendulums reduce the number of times the conductors gallop, and when galloping motions do occur, the amplitudes are found to be less than one third the maximum level experienced by normal untreated conductors.
Above left is a photo of a design of detuning pendulum for a triple bundle line operating at 500 kV.
The photo on the right shows detuning pendulums installed on a 345 kV two conductor bundle transmission line.
If you have concerns regarding galloping on your overhead conductors, let us help you assess the situation and offer a pendulum design to suit your line. Just send us an E-mail and we will contact you promptly to discuss your problem.
Updated October 9, 2006
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