Maine’s New Transmission Study Highlights an Important Evolution in Advanced Conductor Planning
The electric power industry faces a challenge that is becoming increasingly difficult to ignore. Electricity demand is growing faster than much of the infrastructure needed to serve it can be planned, permitted and built, while utilities are simultaneously confronting aging transmission assets, congestion, changing generation patterns, reliability requirements and increasing pressure to keep electricity affordable. A newly released study from the Maine Department of Energy Resources offers a thoughtful perspective on how the industry can respond. The Transmission Infrastructure Study: Landscape Review of Transmission Processes, Needs, and Emerging Opportunities in the State of Maine, prepared by Energy and Environmental Economics (E3), examines Maine and the broader New England transmission system, but many of its conclusions have implications well beyond the region.
One of the report’s most important observations is that utilities have a much larger technology toolbox today than they did when much of the existing transmission system was originally designed. The study recommends that advanced transmission technologies become part of the standard transmission planning process and identifies dynamic line ratings, advanced conductors, power-flow controls, topology optimization and strategically deployed storage among the technologies capable of improving system performance and, in appropriate applications, reducing or deferring more capital-intensive infrastructure investments. This does not diminish the need for new transmission. New transmission corridors will remain essential as electricity demand grows and generation resources change. Rather, the study reinforces an increasingly important idea: expansion and modernization are complementary strategies, and the infrastructure already in service should be evaluated as a strategic resource rather than simply something to be maintained.
An Important Distinction Within the HTLS Category
The study’s discussion of advanced conductors is particularly noteworthy because of how it treats the broader High-Temperature Low-Sag, or HTLS, conductor category. For many years, a wide range of conductors have been grouped together under the HTLS label, sometimes creating the impression that technologies capable of operating at elevated temperatures provide essentially comparable solutions. The Maine study takes a more discerning approach. While the broader HTLS category is acknowledged, its substantive discussion of advanced conductors focuses on composite-core technology and specifically identifies ACCC® Conductor as the most widely deployed design, describing its stronger and lighter carbon- and glass-fiber composite core combined with trapezoidal aluminum strands.
What is equally interesting is what does not become the focus of that discussion. Conventional steel-core HTLS designs such as ACSS are not presented as the centerpiece of the advanced-conductor opportunity described by the report. In that sense, traditional steel-core HTLS technology has effectively been pushed to the side of the study’s forward-looking advanced-conductor discussion, while composite-core technology receives the attention. That should not be interpreted as the study declaring ACSS unusable or inappropriate for every application; it does not. But the distinction is technically important because operating at a higher temperature and fundamentally changing the physical limitations of an overhead conductor are not the same thing.
ACSS can operate at elevated temperatures because its fully annealed aluminum strands are designed to carry electrical load while the steel core provides much of the mechanical strength. ACSS can also be manufactured with compact or trapezoidal aluminum strands, which can increase aluminum content and reduce electrical resistance. But adding aluminum also adds weight, and the underlying steel core retains the thermal-expansion characteristics that contribute to thermal elongation and sag. Consequently, simply increasing allowable operating temperature does not necessarily translate into a comparable increase in useful corridor capacity, particularly when clearances and thermal sag become the limiting factors.
This is precisely why the Maine study’s emphasis on composite-core technology is meaningful. ACCC Conductor changes several of those underlying physical relationships simultaneously. Its lightweight composite core has a substantially lower coefficient of thermal expansion than steel, allowing the conductor to operate at elevated temperatures while maintaining much lower thermal sag. Because the composite core is substantially lighter than steel, more conductive aluminum can also be incorporated into a conductor of comparable diameter and weight. The result is not merely a conductor with a higher temperature rating, but one designed to provide substantially greater capacity while reducing electrical resistance and associated line losses.
That distinction deserves greater attention whenever HTLS technologies are compared. A higher thermal rating is not the same thing as higher delivered power. Conductor sag, resistance, electrical losses, weight, structure loading, clearances and mechanical performance all influence the amount of useful power that can ultimately be moved through a transmission corridor. The Maine study’s focus on these broader performance characteristics rather than temperature capability alone represents an important evolution in the way advanced conductors are being evaluated.
Capacity Is Only Part of the Opportunity
The study appropriately looks beyond ampacity. It identifies reduced sag, lower electrical losses, improved corrosion resistance and even the potential incorporation of optical fiber for monitoring and communications among the benefits associated with advanced conductors. It also recognizes one of reconductoring’s greatest practical advantages: existing towers and rights-of-way can often continue to be utilized, potentially avoiding many of the land acquisition, permitting and environmental challenges associated with developing entirely new transmission corridors. According to the study’s Advanced Transmission Technology summary, reconductoring can cost approximately one-third as much as a complete line rebuild while potentially doubling line capacity, with particularly significant savings where existing structures can be retained.
For utilities facing rapidly growing demand, this introduces an increasingly important consideration: time-to-capacity. A new transmission corridor may ultimately provide enormous transfer capability, but it can require many years to plan, permit and construct. If an existing corridor can be reconductored substantially sooner while delivering the capacity necessary to address near- and medium-term requirements, that option deserves serious evaluation. Reconductoring and new transmission should not be viewed as competing approaches. In some cases, advanced reconductoring can provide urgently needed capacity while larger infrastructure projects move forward; in others, it may defer or eliminate the need for more extensive construction altogether.
Right-Sizing Infrastructure for Tomorrow
Perhaps one of the most important concepts highlighted by the Maine study is right-sizing. ISO New England’s October 2025 Asset Condition List identifies approximately $5.8 billion in planned transmission infrastructure investment through 2032, and the study observes that asset-condition work is expected to be one of the major drivers of transmission spending over the coming decade. That represents an extraordinary opportunity because when utilities are already investing substantial capital to address aging transmission assets, those projects can potentially accomplish much more than restoring the system to its previous capability.
With appropriate planning, an asset-condition project can become an opportunity to increase corridor capacity, reduce electrical losses, improve resilience and prepare infrastructure for anticipated load growth. Rather than asking only what is necessary to satisfy today’s requirement, planners can consider what that same corridor may be required to accomplish over the next 40 or 50 years. The least expensive initial solution is not necessarily the lowest-cost solution over the life of the asset. Rebuilding or upgrading a transmission corridor to meet only today’s requirement may appear economical, but that decision can become extraordinarily expensive if the same infrastructure must be upgraded again a decade later to accommodate load growth that could reasonably have been anticipated.
This is also where conductor selection becomes particularly important. If a utility is already replacing structures, hardware or conductors because of asset condition, simply installing another conventional conductor – or selecting an HTLS conductor primarily because it can tolerate a higher operating temperature – may leave substantial future value on the table. Right-sizing encourages planners to ask a more comprehensive question: if we are going to make this investment anyway, what conductor and system design will provide the greatest capacity, efficiency and flexibility over the full life of the upgraded corridor?
Efficiency Should Be Part of the Capacity Conversation
Electrical efficiency deserves an equally prominent place in that analysis. Transmission losses are not merely an engineering statistic. Every megawatt lost as heat must first be generated, and that means additional generation capacity, fuel, operating expense and infrastructure are required to deliver the same amount of useful electricity to customers. Reducing conductor resistance can therefore provide benefits far beyond a lower percentage-loss number: it can free generating capacity, lower operating costs and allow more of the electricity already being produced to reach load.
The Maine study’s reference to approximately 30 percent lower line losses associated with advanced conductors is therefore particularly significant. It also aligns with a broader recommendation in the report that energy-loss reductions should be considered in comprehensive transmission modeling alongside reliability, resilience, congestion reduction, investment deferral and other system and customer benefits. This reinforces an important principle: transmission technologies should not be evaluated solely by purchase price, temperature rating or nameplate ampacity. Delivered power, electrical losses, sag, structures, implementation time, reliability, future capacity and lifecycle economics all matter.
Advanced Conductors Don’t Need to Win Every Comparison
One of the strongest aspects of the Maine study is that it does not suggest any single technology is the answer to every transmission challenge. Neither does CTC Global. Dynamic line ratings may be particularly useful when conductor capability varies significantly with weather conditions. Power-flow control can help redirect electricity toward underutilized portions of the network. Storage may address particular temporal constraints. New HVAC and HVDC transmission will remain essential where major new regional or interregional transfer capability is required.
Advanced conductors do not need to win every comparison. They need to be included in the comparison – and the comparison needs to examine more than operating temperature. When an existing overhead transmission corridor requires substantially greater capacity, lower sag, improved electrical efficiency and better utilization of existing structures and rights-of-way, the underlying conductor technology matters. The Maine study’s emphasis on composite-core advanced conductors rather than treating all HTLS technologies as functionally equivalent is therefore encouraging. It reflects the engineering principle that technologies should be evaluated according to the physical limitations they actually solve.
More Than Two Decades of Advanced Reconductoring
For more than two decades, CTC Global and its manufacturing, hardware and installation partners have worked with utilities around the world to increase the capacity and efficiency of existing transmission infrastructure using ACCC Conductor. That experience has demonstrated an important principle: transmission modernization does not always require starting over. Existing corridors can frequently be transformed into substantially more productive assets. Advanced conductors can increase capacity, reduced electrical resistance can decrease losses, low thermal sag can help maintain clearances as power flow increases, and existing rights-of-way can often be preserved while avoiding some of the greatest challenges associated with developing entirely new corridors.
The result is not simply more transmission capacity. It is greater infrastructure productivity – more useful power delivered through infrastructure that utilities and their customers have already spent decades building and maintaining.
Getting More From the Grid We Already Have
CTC Global commends the Maine Department of Energy Resources, E3, ISO New England, utilities and the many agencies, organizations and stakeholders whose work contributed to the Transmission Infrastructure Study. Its importance extends beyond any individual technology. The study encourages a broader and more forward-looking approach to transmission planning – one that evaluates advanced technologies alongside conventional infrastructure and considers the multiple benefits an investment can deliver over decades of service.
Billions of dollars will be invested in transmission infrastructure in New England over the coming years, and similar investments are being planned throughout the United States. Electricity demand will continue to evolve, new generation will need to connect, aging assets will need attention, and existing transmission corridors will become increasingly valuable. We should certainly build new transmission where it is needed, but we should also recognize that simply increasing the operating temperature of conventional conductor technology does not necessarily unlock the full potential of those existing corridors.
As utilities prepare to make investments that will remain in service for the next several decades, perhaps the better question is not simply, “How much current can this conductor carry?”
It is:
“How much useful power can this corridor deliver – and how much more can we get from the grid we already have?”
The Maine Transmission Infrastructure Study suggests the answer may be: quite a lot more.
