New Transmission Line Life via Reconductoring
Jason Huang is the CEO and a Board Member of TS Conductors.
Charles Bayless is the retired CEO of Tucson Electric Power and Illinois Power (now part of Ameren Illinois) and a Board Member of TS Conductors.
As our understanding of Earth's climate has dramatically evolved, the urgency to transition away from fossil fuels is undeniable. Simultaneously, the need for additional or renewable generation is skyrocketing as our fossil fuel fleet is aging, new load needs arise such as data centers and electric vehicles, and other industries transition from gas to electricity.
However, a significant bottleneck on this path to a sustainable future is electric power transmission. Despite the increasing need for transmission, the miles of new transmission lines being built have decreased due to the near impossibility of obtaining permits.
Our past is littered with canceled projects like the Northern Pass and Twin State Clean Energy Link, while others, such as the SunZia Southwest Energy Link, struggled to gain permits. The result is that Grid Strategies currently estimates that transmission congestion costs in the U.S. are about twenty billion dollars per year.
Recognizing this situation, FERC issued Order 1920 (and Order 1977) to address the electric power transmission planning and permitting process. Fortunately, a concurrent technical breakthrough, advanced conductors that feature composite core in lieu of steel wires, presents a new pathway to achieve FERC's goals more quickly and at a lower cost than traditional methods. Together, new technology and new regulations can power the future.
The Why Behind Advanced Conductors
Advanced conductors, leveraging the same or the existing structures, can carry up to three times as much power as traditional conductors, cut line losses in half, and are cheaper for both new builds and reconductoring existing lines. With advanced conductors, the transition to a more energy-intensive, renewable economy can often be achieved by upgrading existing lines, decreasing the number of new lines needed to be built, and helping limit associated permitting challenges.
In a traditional ACSR (Aluminum Conductor Steel Reinforced) conductor, the strands are made of hard metal, such as unannealed aluminum, to provide additional physical strength to that furnished by the steel core. While the hard aluminum offers greater strength, it also brings higher electrical resistance and, thus, higher line losses that cause the lines' operating temperatures to increase.
These line losses heat the line and impose a current limit at high ambient temperatures to prevent the line from operating above the annealing temperature of ninety-three-degree Celsius, to avoid the annealing effect in aluminum. Once annealed, the aluminum loses its strength, causing sag and clearance violations; thus, in many areas, such as the Desert Southwest, line currents and power are limited during high temperatures, which is the time of peak load when the line is needed most.
Low-sag carbon cores and the use of pre-annealed aluminum allow advanced conductors to carry high currents, even at high ambient temperatures, facilitating power transfer during high-temperature peak loads without ground clearance or line damage concerns.
Carbon core conductors have little thermal sag. Most of the line tension in the conductor is carried by a carbon fiber composite core, which has a low coefficient of thermal expansion, thus allowing the use of annealed aluminum with lower resistance without the temperature limit in ACSR as the aluminum is already annealed.
Charles Bayless: In one segment of a project, a utility was able to reduce the number of towers from 78 to 59 and use shorter towers due to low-sag characteristics of advanced conductors. They can be made with a larger carbon core, allowing longer spans for applications such as river crossings.
Further, as the carbon fiber core is smaller than a steel core having the same strength, and advanced conductors use keystone-shaped (such as trapezoidal) strands instead of circular strands, lower-resistance aluminum can be used without conductor weight penalty. That is because the carbon composite core only weighs about twenty percent of the weight of an equivalent steel core. These factors combine to make a low-loss conductor that can carry two to three times the power of conventional conductors with about half of the line losses per unit of power transmitted.
Additionally, as the surface of the conductor is smoother than that of ACSR conductor with circular strands, wind loading decreases. This factor, coupled with the stronger core and compact conductor design, makes the conductor more hurricane resistant, while the added core strength allows for larger ice loads in cold weather, and the low-sag and annealed aluminum characteristics help the conductor survive through wildfires without clearance violations or performance deterioration.
Lower line resistance also introduces a new factor in evaluating transmission lines; for example, power plants should have transmission lines evaluated based on life-cycle costs. If line losses on an existing line are twenty megawatts, installing an advanced conductor would reduce losses to approximately ten megawatts for the same current, allowing ten megawatts of plant construction to be permanently deferred.
Thirty megawatts-hour times eight thousand seven hundred sixty hours per year, which represents an operating cost savings of approximately 2.6 million dollars per year, plus associated carbon dioxide savings, are all factors which must now be considered in the economic calculations when evaluating alternatives such as ACSR.
Jason Huang: Advanced conductors can hasten the adoption of renewables as they provide cheaper transmission that allows building of renewables in areas where they will have a higher capacity factor, such as the Desert Southwest for solar power or the Northern Great Plains and coastal areas for wind power.
As advanced conductor cores are significantly lighter, they allow use of a larger conductor without an increase in conductor weight. Thus, reconductoring with a larger conductor size having similar sag and weight characteristics as the original conductor, can quickly increase line capacity by a factor of four, while doing away with need for many new lines and lengthy and expensive tower modifications often required to support the increased weight in conventional reconductoring projects.
New advanced conductors have a totally encapsulated core to effectively protect the carbon fiber from degradation due to moisture, oxidation (especially at high temperatures), UV, or ozone. Further, newer generation advanced conductors are easily installed with ACSR tools, require no additional crew training or special handling, have no special storage requirements, and have built-in tolerance against mistakes for ease of handling and installation.
Advanced conductors are also significantly cheaper when used for new construction. When building a new line, conductors only represent about three to five percent of the total cost. Most of the cost of a new line is for tower design, construction, and lifetime royalty payments to landowners. Due to their strength, low weight, and low sag, advanced conductors allow longer spans to be used.
In one segment of a project, a utility was able to reduce the number of towers from seventy-eight to fifty-nine and use shorter towers due to the low-sag characteristics of advanced conductors. Advanced conductors can be made with a larger carbon core, allowing even longer spans for applications such as river crossings.
Reconductoring with advanced conductors brings significant advantages. By reconductoring the Phoenix to southern California lines, thousands more megawatts of solar can be brought to California. By reconductoring the existing Hydro Quebec-New England DC Line, about as much power would be gained as Northern Pass would have brought to New England, while not requiring new rights-of-way through New Hampshire's pristine forests.
Reconductoring can also efficiently address line congestion and vastly increase flows between areas such as PJM, MISO, New England, et cetera, yielding massive savings without building new transmission lines.
Looking Ahead
Advanced conductors can hasten the adoption of renewables as they provide cheaper transmission that allows building of renewables in areas where they will have a higher capacity factor, such as the Desert Southwest for solar power or the Northern Great Plains and coastal areas for wind power.
Some may question this strategy, but there is ample precedent. We built the lines from Washington and Oregon to Southern California to bring cheap hydropower to California; we built portions of the PJM grid primarily to bring coal power from Western Pennsylvania and West Virginia to the East Coast, and we built the AEP 765-kV system to bring cheap coal power to Chicago and the Midwest.
The same strategy will work for renewable energy, as advanced conductors allow building of a nationwide network (with the necessary AC-DC-AC interconnections) to allow nationwide transfers, which will generate considerable savings.
As FERC seeks to chart a necessary path to the future, advanced conductors will play an important part by offering new, cheaper options. Coupled with microgrids, efficiency improvements, gains in renewable technology, electrification, and renewable market penetration, we have the capability to power tomorrow, today.
