1) Please explain the electrical performance of ClampStar®
2) Please explain the mechanical performance of ClampStar® and its tension rating
There is normally a connector in place, carrying line tension (even if degraded) at the time ClampStar is installed. ClampStar immediately shunts the majority of phase current around the degraded device, thereby reducing its temperature to near ambient, preventing further degradation, and halting any slip that may have occurred. The combination will restore a Class 1 Full Tension rating to the installation.
ClampStar is not intended to be a primary connector, but is designed to operate in conjunction with a primary connector, such as a splice or deadend, to reinforce the primary connector and restore its electrical and mechanical integrity to its original condition, or to exceed that condition.
As is the case with all bolted connectors and strain clamps, because ClampStar utilizes threaded fasteners, and is installed over a conductor, directly engaging only the outer layer of stranding, mechanical performance varies with the type of conductor. A full explanation of this is included in the PDF document titled: “Understanding the Mechanical Performance of ClampStar.”
(Note [a]: This 60% is based on ACSR type conductor. AAC, AAAC, and ACAR will typically approach “full tension” ratings).
(Note [b]: ACSS, ACCC, ACCR, INVAR, Gap Type, SD Type conductors rely on the primary connectors purchase and engagement of the core. ClampStar cannot engage or purchase the core of any conductor, including ACSR, and therefore requires the primary connector to serve as the mechanical anchor).
3) Please explain the affect of Tension load on ClampStar®
Similarly, there is no tension load on the ClampStar® unit when it is applied to shunt tangent suspension and other non-tension clamps and connectors.
The only purpose of ClampStar® units having a tension rating is to assure that the ClampStar® unit will continue to support the mechanical load and maintain conductor integrity in the unlikely event a severely degraded primary connector fails mechanically after ClampStar® installation.
The mechanical integrity of bolted line hardware is dependent upon the application as well as the conductor size and construction. This applies to all types of bolted conductor hardware, including straight line strain clamps, quadrant strain clamps, deadend shoes, etc. Like all bolted line hardware, ClampStar® units have two mechanical strength ratings. One is the UTS or Ultimate Tensile Strength of the ClampStar® body. ClampStar® units sized up through 4/0 AWG (CSR-0609) have UTS ratings that exceed the RBS (Rated Breaking Strength) of the largest conductor on which the ClampStar® unit can be used. The UTS of larger ClampStar® units is at least 70% of the RBS of the largest conductor on which it can be applied.
The conductor holding or slip strength is dependent upon the conductor used. ClampStar® Connector Correctors alone are designed to hold at least 60% RBS of the largest and highest strength conductor for which it is designed. However, most applications will exceed that rating and most AA conductors will be held to at least 95% of the conductor RBS, which is considered to be full tension.
4) Does ClampStar® restore mechanical integrity for full line tension ACSR repairs?
Exactly like bolted deadends, ClampStar units are designed to obtain a minimum of 60% RBS for a given conductor size, not including the connector already in place. i.e., if two cable ends were terminated in respective ends of a ClampStar, having no connector in between, with the ClampStar holding the entire tensile load, it would be intended for 60% minimum of the largest ACSR conductor which it will accommodate. Typically, it will exceed 70% or more, but being an external bolted connection, like all bolted deadends or other line hardware that has been used for over 100 years, it probably will not reach full tension based on the conductor rating, because it does not directly attach to the core. However, the design and intent of ClampStar is to be applied over an aged connector, that although is undoubtedly weakened due to annealing, is presently supporting the full line tension, and now having been protected from further thermal excursions, will contribute sufficiently to the overall assembly, and thus the repaired assembly with ClampStar included can restore the mechanical integrity to that of the original conductor/connector.
For applications on Dead-ends and suspension clamps, a stainless steel tether cable is available to attach through the steel eye, to assure the mechanical integrity of the assembly.
5) What is the purpose of the mechanical tethers and are they needed for all installations?
Typical examples for use of a CSF ClampStar over a deadend would be either to uprate the line for higher ampacity, possibly for contingency conditions, or to restore the electrical integrity to a connector which has been identified as approaching failure, commonly by a hot infrared signature, or high resistance measured in-line.
If the purpose is to uprate the line, and the connectors are known to be mechanically sound, once the ClampStar is installed, the connector will be protected, and will remain cool (only slightly above ambient temperatures) and not be subjected to thermal concern, even at significantly high current levels which raise conductor temperatures to 250°C. Therefore, the connector will continue to serve as the mechanical connection to the insulator.
However, if the deadend had been running hot, or was known to have been subjected to severe fault currents, and was severely weakened mechanically prior to installation of the ClampStar, legitimate concern exists for the mechanical integrity of the deadend. Prudence dictates that it can no longer be relied upon to support the conductor, It is in this instance, where a “Safety Tether” may be used. If that deadend should mechanically fail or separate due the the damage which occurred prior to the installation of the ClampStar, the safety tether effectively picks up the mechanical tensile load on the conductor, and maintains near normal conductor position thereby preventing conductor drop, fault, and outage.
Another example would be a conductor with severely damaged strands in the mouth of a tangent suspension clamp. A safety tether from one ClampStar clamp, through the insulator connection of the clamp, to the opposite ClampStar clamp would ensure that the conductor remains in the air if either the conductor or clamp should fail completely.
It’s important to note that tether ferrules are 7/8” diameter (give or take a few thousandths) and will readily fit through a one inch opening. Hardware for deadend tether fittings cannot readily be “standardized” due to the substantial variety of components, not only between different manufacturers, but even from a single mfg. i.e., vertical eyes, horizontal eyes, clevis ends, adjustable clevis ends, and among those, there are different dimensions (such as diameter of cross-section through component) such as 30K insulator hardware, 50K hardware, etc., that it is almost impossible to make a one fits all, or even a 3 fits all.
At the present time we are working diligently with individual utilities to come up with a bracket for their particular application. We will gladly review hardware, and provide a solution for all inquiries.
6) Would the Safe-T-Link Tether really hold the line tension if the Dead-End failed mechanically?
Regardless of how much tension we now put on the far end of the cable, the spring will not elongate, or be exposed to any additional tension until enough tension is placed on the cable to rupture or overcome the wire.
Of course, if the wire is placed in slack, the spring would stretch until the wire became tight. Unfortunately, a deadend would not stretch very much, but it would likely elongate an eighth of an inch or so before rupture if the tether did not stop it. Typically, additional adverse tension applied to the conductor is going to be in the form of ice, or a tree falling on it, which will pull it downward, and thus the tether, properly placed above the conductor in the same vertical plane, will be subjected to the greater tensile force first.
So, the first objective of the tether is to prevent the original connector from ever being subjected to any additional tensile load – just as the first objective of the ClampStar is to prevent the original connector from ever being subjected to any additional ampacity/thermal load. A ClampStar will very effectively limit the temperature of a connector to something below 75˚C, even at ampacity levels that drive the conductor to 250˚C and beyond! The tether will very effectively limit the tensile load to what the connector is subjected to roughly 30-50% of its rated full tension capacity.
If a span were under 10K tension, and the connector was rated at 40K, the addition of the 20K tether would (within reasonable tolerances) prevent the connector from being exposed to 30K of tension, leaving the already existing 30K margin originally in the connector. As the load increases, movement of the conductor toward the ground, and stretch occurring in the tether, the load would likely equalize somewhere around 40K. Beyond that, we would be relying on the 20K margin still available in the original deadend.
The tether on the suspension clamp works in the same fashion, should there be a large percentage of broken aluminum strands, and perhaps even some core strands – more than just “holding the load in case the original conductor breaks” it prevents the area protected in the suspension clamp from ever being subjected to additional tension.
7) Please explain the fundamentals of ClampStar® applications on Tangent Suspension Clamps with Rods.
The problem is often not detected until conductor failure occurs, because the rods tend to assist in conduction of current, and in so doing, mask the thermal rise which would otherwise be more readily detectable. Thus one might argue that the rods are performing as intended, assuming that fatigue breaks might have occurred earlier had the rods not been in place, and the failure might have occurred earlier. It is difficult to determine the location of broken strands, as they seem to occur in all areas underneath the rods, from close proximity to the clamp, all the way out to nearly the end of the rods with many occurring near the center.
Therefore, the application of ClampStar over suspension systems that incorporate helical rod overlays is recommended to be attached at points directly on the conductor, beyond the end of the rods. Because the ClampStar is attached to the conductor, it moves with it, just as the “clamp portion” of a damper, the added weight serving to disturb the normal wave frequency, and as it has the flex rail attachment, traversing to the opposite side of the suspension system, it transfers a portion of the vibration energy around the normally “fixed point” and dissipates some portion of that energy through the process. Thus by two distinct means, ClampStar serves to dampen the vibration and lessen its severity.
Attaching the ClampStar directly to the conductor assures that (a) the electrical interface will serve to conduct ALL the current in the line if needed with no limits on ampacity, and (b) that should a mechanical need arise, with the addition of a safety tether, the conductor would remain suspended, with almost no detectable differential in sag. In most applications with ACSR type conductor, on normal spans, over cleared right-of-ways, unless there were some concern about the integrity of the core strands, (such as severe corrosion on aged conductor), a safety tether would normally not be required, because the thermal concern will be eliminated by the ClampStar, and the mechanical integrity is unlikely to degrade further. It would perhaps be wise to include a safety tether on “critical” or “high risk” spans such as river crossings, highway crossings, rail crossings, and areas of high pedestrian traffic, where a dropped conductor would cause significant damage or danger. For other types of conductor, such as AAC, not incorporating the safety advantage of a higher strength core, the overall integrity of the conductor must be considered.
The clearance length of the ClampStar is selected by the end user for the application, designated in the part number by the last three digits, i.e. ClampStar CSF-1108-072 is a Flex-Rail ClampStar for conductors typically from just under ¾” diameter up to a maximum diameter of 1.108 inches (795 Drake ACSR); and having 72 inches of clearance between the heads.
Creating a software program to compute the optimal placement of a ClampStar to minimize vibration is extremely complex, as all the mechanical characteristics are not yet quantified. The same may be said for modifying existing vibration analysis software at this time. Therefore, the optimal placement may be slightly different, but at this time, we would recommend placing the ClampStar ends such that the clearance to the end of the helical rods is no less than 3 inches, and typically no greater than 12 inches.
For example, an application of helical rods over 795 Drake ACSR conductor would utilize rods 100 inches long. Thus, an optimal ClampStar for this application would be CSF-1108-112, which would provide 6” clearance beyond the end of the rods.
8) What information is needed to determine the proper ClampStar unit for my application?
1.Type, diameter and size of conductor, i.e., size in kcmil – type, ACSR, AAC, AAAC, ACSS, etc., and preferably with the code name (bird, flower, river, city, animal – or other) from which we can determine everything else. This is needed to determine the proper size of the needed ClampStar, or IF another size might be, could be, or should be substituted. Also an indication for need of tethers. AAC will rarely if ever need tethers, except for deadend or suspension issues.
2. Application! Conductor Damage, Suspension Reinforcement, Connector and Type of splice/deadend; particularly Single Die, or Conventional Two Die, bolted or other. It can be very helpful to get the brand if possible, as this gives a clue to the length, needed to determine the clearance for the ClampStar.
3. Purpose! Is this to repair hot connections, or is this an uprate? Potential application for “Light” versions. Another consideration for tethers.
4. Voltage class of line. Needed to determine corona shielding, and also rigid or flex rail recommendation.
5. Vibration potential – span length – orientation. May determine rigid or flex rail recommendation.
6. Construction of line – single conductor or bundled and how many. Semi-important but could affect shielding options, and gives insight to CSR/CSF as in #4 & 5.
7. Age of the line, if known. May indicate additional potential problems that should be addressed.
8. Operating history, if known. Outages, component failures, other problems.
9. Operating environment. Location, terrain, (sea coast, desert, mountainous, heavily contaminated, etc.).
9) How do I determine if I should use a Flex (CSF) or Rigid (CSR) rail ClampStar unit for my application?
For deadend applications, we would suggest you take a look at the Classic Connectors photo gallery, the first photo is of an improved design specifically for deadends and suspension clamps, which is substantially easier to install, and a few dollars less expensive than the CSF units. It is known as the CSS unit, and should be the first choice for ClampStar applications on deadends or suspension clamps.
10) What is the highest voltage for which ClampStar® is designed?
11) Can ClampStars be ordered with Corona Shields?
Since most 161 kV lines are insulated for 230 kV, the corona shields for 161 and 230kV are the same and are made to fit specific ClampStar units. If you wish to order a complete assembly consisting of a ClampStar unit and the appropriate corona shields please add a “CORXXX” suffix to the ClampStar unit number. Therefore the complete part number for a unit with corona shielding for a 230kV nominal system voltage would be, for example, CSF-1302-048-COR230.
As noted above the shields for 161 and 230kV are identical for specific ClampStar units, as dictated by the number of keepers and the keeper bolt length. The shields fit over the complete keeper array and keeper bolt ends.
For CSF/CSR-1108 and larger units, 230 and 345 kV corona shields are identical due to the keeper bolt length. They should still be ordered based on the intended system voltage but, if the same ClampStar units are used at 230 and 345 kV, it is only necessary to order 345 kV shielding.
500 kV corona shields are also available.
Shields for 345kV and 500kV will be different [larger diameter tubes].
Note: To ensure that shields are used appropriately at 161kV and above, it is more secure to order ClampStar units complete with shielding when necessary.
Auxiliary corona shielding is only required for units up through and including 1302 (1272 kcmil). Units for larger conductors are self-shielded and require no additional corona shielding.
12) How does Corona noise and Radio interference affect ClampStars on 345kV and above?
Positive polarity plumes occur on the positive half cycle and are so named from the appearance of the corona discharges. Positive polarity plume corona is audible and generates significant RIV/TVI.
In laboratory RIV / corona tests two corona levels are usually obtained; corona inception on rising voltage and extinction as the applied voltage is reduced. Extinction generally occurs at a lower voltage than inception due to ionization of the surrounding air. There are two other types of AC corona that occur at lower voltage gradients. Brush at approximately 25 kV rms/cm (64 kV rms/in) and glow at 20 kV rms/cm (50 kV rms/in). Both are also named for their visual appearance and neither generates objectionable fair weather corona.
Under wet conditions virtually all energized electrodes are in corona, including the phase conductors. We have completed RIV tests on 230 kV assemblies with original prototype 230 kV corona shields that resulted in positive polarity corona extinction within 10 kV of nominal 345 kV phase to ground voltage. That shielding was made from 1.5” OD tubing and a Corona Test Report with that shielding on CSF-1108-036 is available. The 345 kV shield is made from 2” OD tubing and the shield for 500 kV is made from 3” OD tubing.
13) Have RIV and corona tests been conducted at 345 and 500 kV?
14) Have there been any 500kV installations completed to date?
15) How does ClampStar® affect damping or galloping and how does it perform under galloping?
NOTE: Damper placement is never an exact science. Typically, utilities obtain placement recommendations from the damper manufacturer and those recommendations will vary, based on the damper characteristics. All are based on energy balance but, it is impossible to locate dampers such that they are on anti-nodes of vibration loops over the range of susceptible laminar wind velocities. It’s a very dynamic environment and damper placement becomes a matter of compromise. For example, the worst possible damper placement is on a vibration node and the reason for two dampers on one end of a deadend span is often to simply be sure that at least one will always be somewhere on the quarter cycle of a vibration loop.
Additionally, we have done some computer vibration analysis with hypothetical conductors, spans, tensions, etc. using a couple of different software packages and, if anyone would like an analysis of a specific case, we would welcome the opportunity to model and analyze it (and we do have the ability to simulate a defined mass anywhere in the span).
16) What is the recommended maximum number of ClampStar units per span of conductor? Example, 5 automatic splices in one span of wire. Is it acceptable to apply 5 ClampStars in one span?
Of course, factors such as; conductor/span length, sag, and splice location must all be considered. 3 ClampStars per span is commonly considered to be the max, but depending on location, perhaps only one or two if they are both in the middle of the span, but if they were all located close to the crossarms, as many as four could be installed and it actually raise the conductor slightly in the center, reducing the sag. Presently, there is no hard rule or standard, every situation may be different.
Consider the following scenario:
Suppose you had a 300 foot distribution span of #2 ACSR conductor. If you installed CSR-0325 ClampStars over the entire span, end to end, there would be 138 of them! Now consider that ice weighs roughly 57.2 lbs/ft3 which is 0.033 lbs/in3. ½” of radial ice on a #2 conductor will be roughly 1.1in3 per inch, and over the length of a CSR-0325, roughly 26 inches will be 29in3 x 0.033 lbs./in3 = 0.96 pounds. This is 27% of the weight of a CSR-0325.
Now, If you figured 27% of those original 138 ClampStar units, it would be 37 ClampStar units. If they were equally spaced, they would be 6 feet apart. That would be the equivalent load on the line as ½” of radial ice, which is the ice loading requirement for Chicago, and not particularly unusual.
37 ClampStars in a 300 foot span! Now, would that create a lot of sag? You bet! Some spans might break with the weight.
The point is, even 6 or 7 ClampStar units would make no difference in the grand scheme of things mechanically. Now when you consider economics, I would think by the time you exceeded six units per span, you would be marginal, compared to the cost of replacing the span.
Of course some things just don’t make good sense. As stated, each span has different characteristics, and trying to calculate all the scenarios possible would take decades – and at the end you would likely conclude that three per span would be the maximum number – but there may be instances where one might use a couple more.
17) Can ClampStars be installed on Self Damping (SD) conductor?
18) Why do we seem to have more splice failures within a few miles of substations than we do at the ends?
19) How does ClampStar effect conductor sag?
20) The ClampStar® part numbers 0883 and 1108 both cover a 477 kcmil conductor, is there a reason to go with the larger ClampStar?
21) What do the last 3 digits in the part number represent?
Example: The nominal uncompressed length of a Burndy splice YDS37RP1 is 26-3/8”, the installed length will be greater due to extrusion of both ends during crimping. The length increase due to extrusion will depend upon the installation tooling and number of crimps (which for YDS37RP1 will likely be either 4 or 12 crimps per end; depending on the die set). Click here for an explanation of the ClampStar part number key code.
22) How is ClampStar® installed regarding nut torque to insure adequate connection?
23) What are ClampStar® “Installation Kits”?
Click here for a photo of the ClampStar Installation Kit.
24) What tools are needed for a successful ClampStar® installation?
Required Equipment and Tools:
- Clean stainless steel wire brush to clean the conductor over both clamping areas.
- Deep well sockets or drivers, as required (depending on the unit being installed). Those with 3/8” torque nuts require a 9/16” socket, while those with ½” torque nuts require a ¾” socket. Some larger units are equipped with torque-limiting set screws which require a T-60 Torx®, 6-point “star” bit, or ¾” socket for installation.
- Torque-limiting nuts and set screws assure proper installation torque with the outer portion shearing at 20 ft-lbs for 3/8” and either 40 or 55 ft-lbs for ½” and set screws.
- Power drills (rattle guns) can be used to significantly reduce installation time.
If removal or relocation of an installed ClampStar is ever needed, a ¾” socket is required for 3/8”, 15/16” for ½”, and a T-45 Torx® or 6-point “star” bit for set screws.
25) What are the characteristics of your proprietary CC² inhibitor?
26) Does your CC² inhibitor work on high temp applications?
27) Where is the CC² inhibitor applied on the shunts and to what thickness?
28) What is “inhibitor washout” and how does it affect ClampStar's CC² inhibitor?
There are many different joint compounds, inhibitors and sealants made from natural and synthetic oil bases. Depending upon the intended application, they may or may not contain grits of various materials, shapes and sizes. As with all compounds, the base oil imparts specific characteristics but the final properties are dependent upon the compounding constituents.
One means of evaluating the susceptibility of inhibitor washout or runout is the inhibitor’s dropping point. Dropping point is the temperature at which the inhibitor becomes fluid enough to drip. It indicates the upper temperature limit at which the inhibitor retains its structure. It does not necessarily indicate the maximum service temperature. There are well-known inhibitors that have dropping points of 50ºC that are commonly recommended for use up to maximum temperatures of 93ºC, depending solely on the film that remains to seal the joint.
Inhibitor washout or runout typically occurs when the joint temperature exceeds the inhibitor dropping point and the base oil begins to run out.
In ClampStar, inhibitor washout and runout of our proprietary CC² Compound is of no concern. It’s designed to withstand the maximum conductor operating temperatures that are being considered. It is non-melting with a dropping point in excess of 260ºC.
29) Can installed ClampStar® units be removed from service and be reinstalled in another location?
All units can be removed from service by removing the keeper nuts with either a ¾” or 15/16” deep well socket, or T-45 Torx® or 6-point “star” bit (set screws can only be loosened with those bits). Retain the flat and spring washers for reuse and visually inspect the unit for any damage. If any damage is evident, do not reuse and contact CC USA. Although the unit can be installed in a new location using the removed nuts, it is recommended that new torque nuts be used to ensure proper installation torque. Reinstallation also requires recoating the conductor grooves with CC² compound. This proprietary compound and replacement torque nuts are available from CC USA. Although it is possible to remove, inspect, and reinstall most units in the field, it is recommended that they be returned to the factory for inspection and reconditioning. Return to the factory is required for units with set screws.