ACCC® Conductor is a high-capacity, low-sag conductor which consists of a carbon fiber composite core encased in a protective fiberglass sheath that is helically wrapped with conductive aluminum strands. It was developed and patented by CTC Global. ACCC® Conductor is a registered trademark of CTC Global.
CTC Global produces all ACCC® Composite Core at its 4 global manufacturing facilities and the ACCC® Conductor is stranded by 35 regional conductor manufacturers worldwide. Currently over 140,000 km of ACCC® Conductor has been installed at over 1,100 project sites.
Conventional conductors typically consist of aluminum strands wrapped around steel core wires. The steel core provides strength so supporting structures can be placed further apart. In some cases, steel core wires are not used, but an aluminum alloy is incorporated to improve the strength of the conductor. Special alloys increase electrical resistance which increases line losses. The ACCC® Conductor offers several advantages compared to conventional conductors with or without steel reinforcement:
- CTC Global’s high-strength composite core allows the incorporation of aluminum strands that provide the greatest conductivity (type 1350-O ≥ 63% IACS*). Various aluminum alloys can decrease conductivity to ≤ 53% IACS (*International Annealed Copper Standard).
- The composite core’s lighter weight (compared to steel core wire) allows the incorporation of ~28% more aluminum without a weight or diameter penalty (using compact trapezoidal strands).
- The composite core’s very low coefficient of thermal expansion enables the ACCC® Conductor to carry additional electrical current without causing excessive line sag that occurs when conventional conductors heat up under increased electrical load.
- The ACCC® Conductor’s additional aluminum content (and superior conductivity) substantially reduces line losses compared to any other conductor of the same diameter and weight.
- The ACCC® Conductor’s non-metallic core also eliminates magnetic hysteresis losses that can be as high as 6% on 3 layer steel core conductor and 20% or more on single layer steel core conductor under high current conditions.
- CTC Global ACCC® Conductor’s composite core is non-corrosive and will not cause a galvanic effect between the core and aluminum strands that can occur with conventional conductors.
- The ACCC® Conductor’s composite core – in conjunction with the smooth surface of the trapezoidal shaped aluminum strands – helps dissipate Aeolian vibration more effectively.
- The dissipation of vibration allows the conductor to be installed at higher initial tensions often without the use of dampers (based on project specific analysis) which serves to extend the effective service life of the conductor.
- The high strength, light weight CTC Global composite core enables installation over long spans which can reduce overall project costs by reducing the number (or height) of the required structures on new transmission or distribution projects.
- A reduction of structures can often minimize environmental impact, simplify the permitting process, and effectively reduce construction time.
- CTC Global ACCC® Conductor’s ability to carry up to twice the current of a conventional conductor makes it ideally suited for increasing the capacity of existing transmission and distribution lines without the need to reinforce or replace existing structures.
- Higher capacity and reduced sag helps improve the overall reliability of the grid.
Carbon and glass fiber composite materials offer superior strength to weight ratios (they are much stronger and lighter than steel). Composite materials do not exhibit the same fatigue failure as metals, nor do they rust, rot, or corrode. Unlike metal alloys, carbon fiber composite materials do not creep over time when subjected to cyclic or continuous high tensile load conditions. They also do not yield (permanently deform) under extreme load conditions. Hybrid carbon and glass fiber composites exhibit elastic behavior and return to their original condition (length) when extreme loads dissipate.
The ACCC® Conductor’s composite core is lighter and stronger than steel or special alloy core which allows the ACCC® Conductor to accommodate greater spans, with a lighter more compact design, and also allows approximately 28% more aluminum to be incorporated into any conductor design without a weight or diameter penalty. The added aluminum content decreases electrical resistance, line losses, fuel consumption (or generation requirement) and can help reduce associated emissions. The ACCC® Conductor offers the least amount of thermal sag compared to any other high temperature low-sag conductor and offers higher capacity with reduced losses compared to any other conductor available today.
The ACCC® Conductor was initially developed as a high temperature low-sag conductor to mitigate thermal sag on transmission lines that were capacity constrained due to sag and clearance limitations that occurred when higher electrical currents caused the conductors to heat up and sag due to their high CTE (coefficient of thermal expansion). The ACCC® Conductor’s low CTE composite core mitigated thermal sag. It therefore allowed existing transmission lines to be upgraded to carry additional current and is considered to be ideally suited for reconductoring projects.
However, due to the ACCC® Conductor’s increased aluminum content, greater strength, and excellent self-damping characteristics, the ACCC® Conductor is now also being utilized on new transmission and distribution lines as it offers increased electrical capacity, decreased line losses, and greater spans between fewer or lower structures. These attributes decrease permitting challenges, simplify tower placement, decrease upfront capital costs, and reduce lifecycle costs. The ACCC® Conductor’s improved efficiency and lower line losses can also decrease fuel consumption and associated GHG emissions as certified by SCS Global Services.
ACCC InfoCore® System
CTC Global’s utility customers asked for a fast, inexpensive, easy, and accurate method to assure the integrity of ACCC® Conductor core after installation. It also allows quality to be extended to the field and provides a foundation for future innovation.
The ACCC InfoCore® System consists of three components: the ACCC® Core with embedded fiber optic filaments, the Confirmation Kit and the Information Management System. The embedded fiber optic filaments are integrated into the ACCC® Core allowing them to function as one structure. This means that if the ACCC® Core breaks then the fiber optic filaments will too and vice versa. The Confirmation Kit includes the tools needed to prepare the ACCC® Conductor and confirm that it was handled and installed correctly. The captured data is then uploaded to the CTC Cloud Server where the registered user can generate reports.
The process begins by preparing the ACCC® Core at each end, using tools provided in the ACCC InfoCore® Confirmation Kit. Then:
- The emitter is attached to one end of the ACCC® Core.
- The detector is attached to the other end.
- The controller (on the ground) operates the system and records the results.
Core preparation and inspection takes less than five minutes.
There is no price difference at this time, with the exception of the confirmation cost which is negligible. Keep in mind that CTC Global’s authorized manufacturing partners set the price of the finished product based on their production costs.
Product lead times can vary depending upon project size, location and supplier backlog. The time to produce ACCC® Core vs ACCC InfoCore® Core is identical.
ACCC® Conductor uses specially designed hardware that delivers worry-free performance and outstanding longevity in any environment. Due to the ACCC® Conductor’s high capacity, dead-ends and splices are typically larger than conventional hardware to dissipate heat. ACCC® Dead-ends and splices use an integrated collet design which grips the composite core, while outer aluminum sleeves are compressed onto the conductive aluminum strands using conventional compression dies and presses. Other designs are available for lower voltage applications. CTC Global generally recommends armor rod and AGS suspension clamps which is outlined in our Installation Guidelines document.
The ACCC® Conductor requires specially designed dead-ends and splices. A dead-end assembly consists of a collet housing, collet, and threaded eyebolt. During installation, a lineman removes several inches of the outer aluminum strands to expose the composite core. The collet and collet housing are placed over the core and the threaded eyebolt is inserted into the collet housing (also threaded) and tightened with a pair of crescent wrenches. Tightening the eyebolt into the collet housing tightens the collet and allows it to grip the core. A conventional (though somewhat larger) aluminum sleeve is placed over the conductive aluminum strands and collet / eyebolt assembly and compressed with a conventional 60 ton press using a compression die sized for the particular conductor being installed. The compression sleeve has a jumper pad located adjacent to the eyebolt which allows a jumper to be attached with a standard NEMA four bolt pattern, or other bolt pattern as specified by the customer. Dead-ends are back pressed to prevent conductor bird caging.
Full tension splices contain two collet assemblies that are installed using the same procedure as is used with dead-ends. However, instead of tightening the collets down with the threaded eyebolt ends, a free rotating threaded coupler is used in this case. Once the collet assemblies have been attached and tightened down, a similar outer aluminum sleeve is placed over the collet assemblies and a 60 ton press is used to crimp the ends of the outer sleeve to the aluminum strands on either side of the inner collet assemblies. It is noteworthy that the added mass of dead-ends and splices allows them to operate at approximately one-half of the temperature of the conductor which helps ensure efficiency, performance, reliability, and longevity.
Unlike steel or aluminum wires that will plastically deform and yield, hybrid carbon fiber composites are fully elastic, but can be damaged by impact. For instance, if you pound a round steel or aluminum wire with a hammer, the wire will flatten out. If you pound a round composite core you could damage it. Compression devices placed directly on a composite core may cause damage. CTC Global’s patented collet design will not damage the core and allows core elasticity without loss of grip or potentially damaging stress concentration.
ACCC® Conductor dissipates vibration energy more effectively than conventional round wire conductor designs, so in certain cases dampers may be unnecessary. However, the ACCC® Conductor’s greater tensile strength is often utilized to increase spans under higher tensile loads. It is therefore recommended that designers contact CTC Global or a damper manufacturer to secure recommendations specific to their project. When dampers are recommended for a specific project the exact location of damper placement is specified. Dampers are generally mounted directly on armor rod.
CTC Global’s hardware database allows you to select your project’s region and conductor size and it will provide you with a catalogue of ACCC® Hardware available from CTC Global’s authorized hardware manufactures in your area, along with contact information.
CTC Global’s engineering team can address electrical and mechanical questions, perform conductor comparisons, assist with PLS CADD™, Sag10™, CCP™ or other software design programs, and address other questions that relate to the conductor, ancillary hardware, or project economics.
Through substantial testing, field experience, and engineering interaction, CTC Global and other entities have well quantified the ACCC® Conductor’s performance as it relates to tensile strength, flexural strength, vibration dissipation, ice load capacity, and electrical performance. The data compiled allows transmission line designers to take full advantage of the ACCC® Conductor’s high electrical capacity, reduced line losses, high strength, and low-sag. The data compiled allows transmission engineers (both electrical and mechanical) to accurately assess ACCC® Conductor suitability for any project. Industry tools such as PLS CADD™ can be readily utilized to support the engineering process. CTC Global’s application engineers are also available to assist with analysis, comparisons, economic modeling and general support. They can also provide life cycle cost analysis based on upfront capital costs, line losses / GHG emission reductions, increased capacity, improved longevity and other attributes of the ACCC® Conductor at no additional cost.
CCP™ (Conductor Comparison Program) Software was created by CTC Global to help system planners and engineers compare the ampacity, line losses, thermal and ice load sag, and economic aspects of nearly any conductor type and size, so the numerous advantages of the ACCC® Conductor can be fully realized.
ACCC® Conductor is installed using conventional tools, techniques and equipment. While the installation of ACCC® Dead-ends and splices is slightly different than the installation of conventional ACSR, ACSS or AAAC fittings, the conductors are installed in a similar fashion. As with other types of conductors, it is important to follow IEEE 524 installation guidelines and select appropriately sized sheave wheels based on conductor diameter, pulling tension, and angle of the conductor’s entry in / out of the sheave wheels. As with ACSS conductor, ACCC® Conductors use fully annealed aluminum strands that are slightly softer than non-annealed, hardened, or special alloy aluminum. Sheave wheels should be properly aligned so that scuffing of the aluminum strands does not occur, and the conductor should not be dragged across the ground that could damage the aluminum strands and induce corona on an energized line. Additionally, as the ACCC® Conductor’s composite core is essentially non-conductive, care must be exercised such that grounding clamps are placed directly on the aluminum strands.
CTC Global provides installation training for all customers worldwide. ACCC℠ Installation Training is delivered by ACCC® Certified Master Installers and includes all safety and procedural aspects that are unique to ACCC® Conductor and associated hardware. While we assume that the crews being trained are generally experienced linemen, safety basics are reviewed. The program begins with a classroom review of the important differences between the ACCC® Conductor and other conductors and how those drive the few but important changes in industry standard installation practices. The classroom session is followed by a hands-on demonstration of dead end and splice assembly. These two elements take about a day, depending on class size. The third element is on-the-job training, wherein the Master Installer actually goes to the jobsite with his class for the first couple of sections or pulls. He will reinforce the classroom lessons and correct practices, is available to answer questions and advise on any special conditions, and to verify the effectiveness of the training.
Prior to the start of construction, our field support staff will provide specific tools and equipment lists. Then, we will review those lists with your key installation staff and contractors to ensure that proper equipment and tools are procured and allocated for your installation.
CTC Global offers ACCC℠ On Site Service (OSS℠), wherein an ACCC Certified Master Installer assists the site supervision by providing guidance and expert advice. The Master Installers are extremely experienced with tensioned overhead stringing in general and ACCC® Conductor installations in particular, and the OSS℠ makes this expertise available to your crews and supervision to help ensure a reliable and efficient installation outcome.