Utility Applications
1. AR WINDAMPER® Anti-Galloping System
When galloping is present, aerodynamic forces act upon the AR WINDAMPER® device causing the conductor to twist along its axis changing the leading edge of the airfoil of ice on the conductor in relation to the wind's angle of attack. With less than a 10-degree twist, this action is sufficient to shed aerodynamic lift known as galloping. This is the engineering premise of all AR PRODUCTS, LLC low-frequency vibration technology.
2. AR TWISTER Anti-Galloping System
In this application, the MOD III AR TWISTER is installed from a bucket truck on a hot transmission line operating at 115kV. The device is clamped to armor rods installed first to protect the aluminum conductor from damage. The installation point is at 1/3rd span. Only one device is usually needed per span on each conductor. It is suspended from the boom upside down and moved to a position over the armor rods, previously installed.
After the clamps are secured to the rods the sling is released and the weight drops to the side. The final position depends upon the torsional stiffness of the conductor, previously calculated. The final position of 90 to 120 degrees from vertical is ideal.
Upon exposure to galloping due to ice and wind the device moves up and down with the conductor incurring acceleration forces both up and down. Such forces twist the conductor causing dynamic changes of the wind angle of attack. Because the frozen ice behaves like an airfoil, aerodynamically, the dynamic lift force along the span is operating to oppose the motion and to reduce or prevent galloping of the span. Thus, the angle of attack the relation to wind direction has been changed and lift of the conductor is cancelled.
3. Pacificorp installation of AR TWISTER and AR SPACER TWISTER Anti-Galloping System
An analysis of the PacifiCorp Worland to Thermopolis line in Wyoming determined the high probability of conductor clashing. The construction consisted of T&D circuits on a single set of wood poles with the high-voltage 115-kV line constructed over the 34.5-kV distribution line. Span lengths were between 290 ft and 350 ft. Ceramic post insulators support the transmission conductor 795 kcmil 26/7 ACSR DRAKE, while pin insulators on cross-arms support the distribution conductor 477 kcmil 19-strand ACC COSMOS.
For the distribution circuit, the cross-arm separation was 5 ft with the top cross-arm pin insulators installed 54 inches on either side of the pole centerline, and the bottom cross-arm pin insulators installed 43 inches on either side of the pole. Two phases were mounted on the top cross-arm, and the third phase and neutral were mounted on the bottom arm. Preformed ties and line guards were used to protect the conductor at the pin insulators.
The anti-gallop device, MOD II AR Spacer Twister, was installed at the one-third span points, separating the phase wires from one another and from the neutral. The Spacer Twister consists of a Sediver 60-inch insulator with eye connectors on both ends. The endpoint clamps attach to the insulator and install at an angle to the conductor to produce twisting whenever galloping occurs.
For the transmission line, one MOD III AR Twister was also installed at the one-third span point. The Twister consists of a 20-lb aluminum weight supported by aluminum bracket assemblies mating to an aluminum alligator-gripping clamp. The unit is mounted upside down over armor rods and allowed to fall by gravity to either side of the conductor, reaching equilibrium between 90 and 120 degrees.
4. AR SPACER DAMPER Anti-Galloping System
The AR MOD-II SPACERS DAMPER system reduces low-frequency ice induced galloping of bundled conductor transmission circuits. This unique design also mitigates sub-conductor oscillation, as well as auto-rotation of the bundle.
Two units per span are installed at the one-third span points on opposite sides of the conductor with the spacer damper ring in a vertical plane, and one clamp attached over furnished armor rods to each sub-conductor. The clamps of the AR SPACER DAMPER are designed to swivel about the spacer damper ring, allowing the unit to attach to the vertical bundles having spacing differences along the span.
Torque stiffness of the sub-conductor keeps the unit in the correct alignment after being installed. It is this torque stiffness which works in tandem with the AR SPACER DAMPER device to allow the sub-conductor to twist.
When galloping is present, the up and down motion induces twisting of the conductor due to the eccentric offset of the AR SPACER DAMPER unit. With less than a 10 degree twist, this action is sufficient to cause the airfoil of ice present on the conductor to shed aerodynamic lift.
Electric Utility Articles and Video:
Power Line Damage, Electrical Outages, Reduced in the "Sleet Belt"
Electrical World: Anti-Galloping Devices
PacifiCorp gets a Grip on Galloping Conductors
Twister System Prototype Demonstration
Windamper® / Twister System to Reduce Mechanical Vibration
Electric Light and Power - January 1984
Bethlehem Steel Success Story: Technology Showcase
Bethlehem Steel Burns Harbor Video
Windamper® Comparison to Other Devices