AR Products are patented, tested and proven for
AR Products specializes in galloping control solutions. Variations in wind, ice, dynamic structural properties and conductor stiffness under changing environmental conditions makes galloping difficult to predict. The AR method of application and proprietary twisting technology of AR dampers has been shown to reduce predicted peak-to-peak galloping amplitude by more than 50%.
Understanding Twisting Technology
Twisting the conductor as a method to control galloping is a complex challenge. AR Products specializes in designing a solution suitable for the unique characteristics and features of the line. Experience has shown that dampers that twist the conductor will act to arrest galloping, rather than merely decrease galloping amplitude.
How Twisting works to control galloping. As the wind angle of attack creates galloping conditions, the gravitational force on the damper will cause the conductor to start twisting, thus dumping off the aerodynamic lift. AR Products solutions control galloping by twisting the conductor, a methodology based on two key principles: acceleration and inertia.
Using Twisting as a Method to Control Galloping. Twisting technology differentiates AR Products anti-galloping solutions from all others. The initial twist of the line at product installation induces the conductor to rotate through large angles when ice and wind conditions occur, so that galloping never gets going.
This initial twist and gravitational forces on the anti-galloping dampers will cause the conductor to start twisting more during wind and ice conditions, effectively dumping off the aerodynamic lift that induces galloping.
AR Products technology is grounded in fundamental, scientific and engineering principles.
On-line devices tame wind- and -ice induced conductor movement.
A field test to show how twisting controls galloping amplitude
Holding Strength.* Two models of AR Clamps have been tested for holding strength. Alligator grip clamps slipped at a tensile load of 1000 lbs. Nutcracker grip clamp slipped at a tensile load of 1200 lbs.
Corona and RIV Testing* AR Clamps and Spacer Dampers have been tested for RIV measurements and corona photographs. RIV and Corona tests indicate AR Clamps are free of corona ad RIV well above 345kV.
Insulator Rod Testing.* Insulator rods used in the AR Spacer Twister have been tested for compressive strength to establish column-buckling behavior. The tensile test of the 5/8” rod revealed an ultimate load of 35,000 lbs. The rods behave as an elastic column under compression load.
Galloping and Vibration Performance Testing.* AR Twister have been tested to qualify for performance in controlling Aeolian vibration and galloping on energized high voltage transmission lines. Testing also included corona and RIV.
Dynamic & Mechanical Testing.* AR Clamps, Twister and Spacer Damper have been test for mechanical characteristics and tensile strength.
All tests were completed in an independent laboratory.
Research Consulting Associates has conducted scores of research and development projects for private industry entities, as well as Federal Government agencies, including the NSF, DOE and NASA. Research includes examining methods for effectively controlling high-frequency vibration and low frequency galloping of power lines. Field studies include measuring product performance and the analysis of data on galloping.
Studying the Probability of Galloping. In 1998, Research Consulting Associates pioneered one of the most comprehensive studies on galloping based on field data collected over 3 years. Funded by the Department of Energy, the study analyzed data collected by Ontario Hydro on the field performance of two anti-galloping dampers. Several hundred units of each damper were installed on the utility’s single circuit line for observation. One conclusion of this study was that the probability of galloping is a linear function. The other lesson learned from both this study, and experience, is that galloping is a phenomenon that cannot be controlled in a single span approach. Observed galloping in one span may have started in an adjacent one, and it may then relay the motion in both directions ahead and back. Treating one span where galloping has been observed does guarantee that the line will not gallop again nor will it protect adjacent spans from galloping. See A Study of Galloping Conductors on 230kV Transmission Line
Twister. PacifiCorp analyzed the Worland to Thermopolis line in Wyoming to determine the probability of conductor clashing. Field testing was initiated to compare effective galloping control by the AR Spacer Twister (polymer interphase with articulating clamps) and the AR Twister MOD3 (20lbs aluminum weight). These tests revealed that both devices eliminated galloping flashover. See PacifiCorp gets a Grip on Galloping Conductors, T&D World/April 2002.
Spacer Damper. A series of field tests were undertaken during December 1985 in Littleton, New Hampshire, for the New England Power Company to measure the Aeolian vibration of a new triple bundle DC transmission line. The objective was to evaluate the performance of the damping devices installed on the Phase I transmission line. These tests provided design data for specifying vibration control devices for the Phase II line. Conclusions of the study included:
• vibration of a single conductor is 4-5 times less than the vibration of the triple bundle having five spacer-dampers of a particular type, and
• the level of vibration of the bundle having only one spacer-damper at mid-span and one end-point damper per sub-conductor is the same as a single conductor. See Vibration of Bundled and Single Conductors: A Comparative Case Study
How does twisting help control galloping?
All AR products offer galloping control by twisting the conductor. This methodology operates on two key principles – acceleration and inertia.
Experience has shown that twisting the conductor will arrest galloping rather than decrease galloping amplitude. Generally a conductor will gallop up to 100% of sag and gallop down a percentage too. A twisting mechanism effectively controls galloping by interrupting the cycle before it gets going. As the angle of wind attack creates galloping conditions, the gravitational force on the AR damper causes the conductor to start twisting and effectively dumping off the aerodynamic lift. AR Products are not intended to decrease the amplitude of galloping, rather all are designed to interrupt galloping so that higher amplitudes are not achieved.
What are the electrical impacts (corona) of AR product technology?
When galloping control systems are used on low and medium voltage lines (115kV-230kV) corona is not a factor. When voltages are higher (345kV, 500kV) the AR Products are corona protected. To further protect the conductor most AR products are installed with line guards or Armor Rods.
What is the mechanism of ice shedding/how many galloping cycles occur?
These are two different phenomena. Galloping is a steady state of large amplitude motion. Ice shedding is an intermittent phenomenon that causes the conductor to jump when the ice falls from the conductor.
The mechanism of ice shedding - ice sheds in large chunks which causes the span to jump or gallop. Ice shedding and its affects have negligible effect in causing galloping.
We have little data or experimental evidence on the number of galloping cycles. Because the AR Twister is designed for a low frequency conductor, you get only one cycle every 5-7 seconds depending upon the span length. AR Twister interrupts the conditions that lead to galloping so there are no cycles to get underway.
What is the difference between galloping and Aeolian vibration?
Galloping is a low frequency, high amplitude wind-induced motion of a single conductor. Aeolian vibration is a high frequency, low amplitude motion caused by smooth laminar winds flowing across a cable. Uncontrolled galloping at high amplitudes can cause flashover and outages. Vibration that is unchecked can cause wear and structural damage to structures, hardware and the conductor itself.
Is there any impact on Aeolian vibration due to the use of AR Twisters?
Yes, AR Twisters are designed to control Aeolian vibration and galloping at the same time, by the same unit. This is a key element of the damper.
How does the MOD2 Spacer Damper control vibration and galloping?
The MOD2 controls galloping by the twisting mechanism in the clamps. The installation methodology is also a key factor in controlling high amplitude galloping. When the conductor experiences high frequency vibration, the conductor moves against the clamp. The clamp itself creates an impact with the steel hoop, thereby absorbing the transferred energy. In addition that motion creates movement of the coil springs, which also impact the hoop, adding more energy dissipation. Such features of the design eliminates the need for the dog-bone or any other high frequency damper.
Which AR Products use a twisting mechanism?
Low Frequency Galloping Control Systems all deliver an initial twist of the conductor at installation. These product solutions include WINDAMPER, AR Twisters, AR MOD2 Spacer Dampers, and AR Lightweight Spacer Dampers.
High Frequency Vibration Control Systems offer control for Aeolian vibration. These product solutions include Sandamper, AR Snubber, AR Ring Damper. AR Dual Dampers and AR Twisters control galloping in addition to Aeolian vibration.
What is the life cycle cost of AR Products?
The average service life value of the AR Twister is 12-15 years or more. Many WINDAMPERS have been in service for more than 30 years. If routine maintenance plans are followed for Sandampers, the service life value can be 25 years or more. AR MOD2 Spacer Dampers have been in service for more than 12 years.
How do AR Products compare with Interphase Spacers?
The key difference between interphase spacers and the AR product line is the clamp. For example, the AR Twister clamp is responsible for rotating the conductor through large angles so that galloping never gets going. The interphase spacers are designed to keep the conductors separated to avoid flashover. The net result of using the interphase spacer is that the two lines tend to gallop in synchrony. Side by Side comparison AR Twister – Interphase Spacers.
How does the AR Twister compare with dog-bone dampers?
The AR Twister is a galloping control damper that also protects the line from Aeolian vibration because of how it is installed. Dog-bone dampers are designed to protect the line from vibration and the damage caused by unchecked vibration (structural wear and tear). Dog-bone dampers do not mitigate galloping.
What is the decrease in galloping amplitude by AR Products?
In a publication issued by a CIGRE work group in 2005, it was reported that during a field test by EPRI, the Windamper was reported to reduce galloping amplitude by 75%. When AR Products are installed as a system across at least 10 consecutive spans it is possible to achieve a reduction in peak-to-peak galloping amplitude of more than 50%
MEANS FOR DAMPING VIBRATIONS OF POWER TRANSMISSION LINES
United States Patent 3,440,328
ANTI-GALLOPING DEVICE, TRANSMISSION LINE COMBINED THEREWITH, AND METHODS
United States Patent 4,777,327
Twisting as a Method for Controlling Galloping of Transmission Lines
TRANSMISSION LINE SPACER DAMPER DEVICE
United States Patent 5,362,920
AR Spacer Damper for Twin, Triple and Quad Bundled Transmission Lines
METHOD OF SPACING TRANSMISSION LINE SUBCONDUCTORS
United States Patent 5,488,920
Method for Controlling Galloping of Bundled Transmission Lines
TRANSMISSION LINE SPACER DAMPER DEVICE MOD-II
United States Patent 5,721,393
AR Spacer Damper MOD2
TRANSMISSION LINE SPACER TWISTER DEVICE
United States Patent 6,008,453
AR Spacer Twister