Evaluating advanced cores for optimal grid capacity: a critical review

Transmission lines near Los Angeles, California (Courtesy: Robert Thiemann/Unsplash)

Contributed by Andy McComas, Institutional Director of North American Lineman Training Center (NALTC); and Dan Berkowitz, head of Bekaert’s North American Energy marketing & strategy department

The ever-increasing demand for electricity and the shift toward renewable energy sources are reshaping the landscape of power grid infrastructure. Central to this transformation is the selection of conductors, which are crucial for efficient and reliable electricity transmission.

This article offers a detailed examination of steel core conductors and their newer counterparts, emphasizing capacity, resiliency, sustainability, and cost to identify the best solutions for today’s grid challenges. 

Importance of conductor choice

Selecting the appropriate conductor is vital for enhancing grid capacity, ensuring resiliency, and maintaining cost-effectiveness. Aluminum Conductor Steel Reinforced (ACSR) conductors have traditionally been the standard in the industry due to their cost efficiency, strength, and versatility. However, with evolving grid demands, new materials like carbon fiber composite cores (CFC) are being considered for their unique characteristics. 

Conductors are assessed based on four main criteria: capacity, resiliency, sustainability, and cost.

Comparative analysis of different conductor types

The white paper compares various conductor types, including ACSR, ACSS (Aluminum Conductor Steel Supported), ACCFCS (Aluminum Conductor Carbon Fiber Composite Supported), and ACCFCR (Aluminum Conductor Carbon Fiber Composite Reinforced). Here’s an in-depth look at their performance: 

Capacity: 

ACSS/TW/MA5, with its high-temperature mischmetal coated steel core, boasts the highest capacity due to its ability to operate at up to 250°C. ACCFCS/TW features a polymer matrix core that limits its operating temperature to 180°C, resulting in lower capacity. ACCFCR/TW, similar to ACCFCS/TW but with a hard aluminum-zirconium alloy, also operates at a maximum of 180°C, offering slightly lower capacity. ACSR, limited to 100°C due to metallurgical constraints, provides the lowest capacity among the compared conductors.

Resiliency:

ACSR ranks highest in resiliency due to its robust steel core and hard aluminum strands, making it highly durable and easy to repair after damage. ACSS/TW/MA5 offers good resiliency with its multi-strand steel core but lacks the structural redundancy of ACSR. ACCFCR/TW and ACCFCS/TW are less resilient due to their single-strand cores, which lack redundancy and require specialized tools for restoration, leading to longer recovery times.

Sustainability:

ACSR and ACSS lead in sustainability with their long service lives, use of abundant materials, and high recyclability. ACCFCS/TW is less sustainable due to the complex recycling process of composite cores. ACCFCR/TW ranks lowest because of the lower recycling value of alloy aluminum and higher line losses.

Cost:

ACSR remains the most cost-effective for new structures due to its low initial cost. ACSS/TW/MA5 and composite core options are more competitive in reconductor projects where increasing capacity without replacing existing structures is necessary. Composite cores are less cost-effective due to their higher initial costs. 

Real-world reconductor scenarios

To illustrate the practical application of these conductors, a reconductor scenario was analyzed. In this example, a 795 kcmil 26/7 “Drake” ACSR conductor, which had reached its capacity limit, was compared with alternative conductors of similar diameter and cost. The 795 kcmil ACSS option provided a 66% capacity increase for a 10% cost increase. The 959.6 kcmil ACSS/TW/MA5 option increased capacity by 82% for a 40% cost increase. The composite core option offered a 68% capacity increase but doubled the cost, making it less competitive unless the cost of structural changes for steel core options exceeded its premium.

In a cost-constrained scenario, the 1026 kcmil composite core provided a 68% capacity increase for a 200% cost increase. The 1622 kcmil ACSS/TW/MA5 provided a 148% capacity increase for the same cost but had a larger diameter, potentially requiring structural remediation.

Comparing the cost per amp of an ACSS/TW/MA3 conductor vs the cost per amp of an ACCC “Drake” conductor. The ACSS/TW/MA3 conductor provides the transmission line with nearly 3 times cost per amps savings than the ACCC “Drake” conductor. 

Environmental and practical considerations

The selection of conductors involves both environmental and practical considerations. Composite core conductors, despite being innovative, face significant challenges related to their recycling processes and the environmental impact of their production. On the other hand, steel core conductors benefit from a well-established recycling infrastructure, making them more environmentally friendly over their entire lifecycle. Additionally, the installation and maintenance of composite core conductors require specialized tools and training, adding to the overall cost and complexity. This contrasts with the familiarity and ease of handling steel core conductors, which can be a decisive factor in regions with limited technical expertise.

Composite core conductors also suffer from lower resiliency compared to their steel core counterparts. Their single-strand cores lack redundancy, making them more vulnerable to damage and requiring longer restoration times. This is a critical drawback in areas prone to extreme weather events or where quick recovery of power lines is essential.

Future trends and innovations

The future of grid infrastructure will likely see a blend of these advanced conductor technologies. Research and development are continuously improving the performance and reducing the costs of composite core conductors. However, these advancements must overcome significant hurdles related to cost and practicality before they can become viable alternatives to steel core conductors. Innovations such as enhanced materials for better thermal performance and the development of hybrid conductors that combine the strengths of both steel and composite cores are on the horizon.

Utilities and grid operators must stay abreast of these advancements to make informed decisions that balance immediate needs with long-term sustainability and cost-effectiveness. Pilot projects and phased implementations can help in evaluating the practical benefits and challenges of new conductor technologies in real-world settings.

In conclusion

Steel core conductors, particularly ACSS/TW/MA5, demonstrate superior capacity, resiliency, and cost-effectiveness in most scenarios. Composite core conductors, while offering some advantages in specific applications, generally fall short due to higher costs, lower overall performance, and significant practical challenges. As the energy industry continues to evolve, the choice of conductor will remain crucial in balancing capacity, cost, and sustainability. This comprehensive analysis provides a clear roadmap for utilities and grid operators to make informed decisions, ensuring that their infrastructure is robust, resilient, and ready to meet future demands.

With ongoing advancements and a keen focus on environmental impacts, the future of grid infrastructure promises to be more efficient, sustainable, and capable of supporting the growing energy demands of a modern society. Conductors, as the backbone of power transmission, will continue to play a pivotal role in this evolution, making their selection and deployment a critical focus for the energy industry.


About the authors

Andy McComas acts as Institutional Director of North American Lineman Training Center (NALTC) in McEwen, Tennessee.  NALTC is a post-secondary educational facility accredited and mandated by the Tennessee Higher Education Commission and is one of the largest pre-apprentice lineman training programs in the United States.  NALTC has trained thousands of entry-level apprentices who are seeking to become distribution and transmission linemen in the exciting and lucrative electrical line-worker profession.   

Dan Berkowitz currently leads the North American Energy marketing & strategy department for Bekaert, focused on driving the Power Transmissions ACSS/ACSR Conductor growth. Dan has held many product management roles throughout his career related to the Energy Industry. His aspirations are to deliver the most efficient and economical solution that brings our electric grid into the future.

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