There’s a great deal of work being done on the power delivery system to assist the world’s transitioning from fossil-fuels to clean energy. The grid needs modernization from its distribution networks to its bulk transmission systems. Worldwide, there are proposals to establish transmission corridors, refurbish distribution lines, and add overall system capacity. Exacerbating these challenges is the growing demand for more electricity worldwide, but the 800-pound gorilla in the room is the grid’s aging bulk transmission system.
When it comes to aging infrastructure, the power delivery system leads the pack. It has been identified as a major target for being overhauled and enhanced. Last year the IEA (International Energy Agency) released a report titled “Electricity Grids and Secure Energy Transitions.” It shocked readers by stating that the world needed to add or refurbish over 50 million miles (80 million km) of transmission lines by 2040 to meet decarbonization goals. The IEA report went on to say, “That is the equivalent of the entire existing global grid.”
Just thinking about building and/or refurbishing thousands of miles can be an intimidating responsibility. The IEA study isn’t the only attention-grabbing report that has been published lately on the necessity of improving the robustness of the world’s bulk transmission systems. Each study comes with a slightly different approach, but the conclusions are pretty much the same. Something needs to be done to the overall bulk transmission system and it has to happen quickly. The IEA objective of 2040 has been met with skepticism on the part of utilities, ISOs (Independent System Operators), and RTOs (Regional Transmission Organizations) alike.
They understand that building a single large-scale, high-voltage transmission project can take over 10 years. Imagine the effect that multiple large-scale transmission projects taking place concurrently worldwide will have on the industry. Supply-chain issues alone would be insurmountable not to mention their cost. Wouldn’t it be amazing if there was a technology available that increases transmission capacity and modernizes the transmission infrastructure simultaneously?
Transfer Capacity
Well, it does, thanks to the advancements in wire technologies. Modern conductors have been developed to attain the maximum power capacity with the lowest sag and the most tensile strength. It’s called advanced conductor technology, but it covers many applications. The most interest for this discussion is the overhead conductor portion. They’re attracting the power delivery industry’s interest for both new construction and reconductoring projects. Since speed is a leading consideration, let’s focus on the reconductoring of existing transmission lines as our prime interest.
A few months ago, FERC (Federal Energy Regulatory Commission) issued its Order No. 1920, “Building for the Future Through Electric Regional Transmission Planning and Cost Allocation.” Order 1920 addresses many of the critical issues affecting the transmission grid. Basically, the approximately 1,300 page Order 1920 tackles the remedies for what FERC says are the deficiencies in the existing processes when it comes to planning, building and paying for transmission facilities needed for today and the future.
One of the more interesting reforms is alternative transmission technologies. Providers have to include these technologies when evaluating new regional transmission facilities and upgrades to existing facilities. Providers are defined as ISOs, RTOs, and utilities not included in ISOs or RTOs. It goes so far as to say that providers must explain why or why not these technologies were incorporated into the selected transmission facilities.
Modern Material Science
The upgrades mentioned in Order 1920 also include reconductoring existing transmission. Logically advanced conductors should be the go-to technology when it comes to upgrading transmission facilities. Modern advanced conductors take advantage of the latest innovations for increasing the amount of power they can move to market. FERC says advanced conductors include, but are not limited to, “superconducting cables, advanced composite conductors, advanced steel cores, high temperature low-sag conductors, fiber optic temperature sensing conductors, and advanced overhead conductors.”
Let’s keep this discussion focused on advanced overhead conductors. That would allow an in-depth look at this wire technology. The recent study performed by the Idaho National Laboratory (INL) is a good place to start. It’s titled, “Advanced Conductor Scan Report,” and is available at INLs’ website for anyone interested.
Examining the INL report revealed some interesting details concerning these innovative wires. Many of the advanced conductors listed by INL should be familiar to readers. They include ACSR (Aluminum Conductor Steel Reinforced), AAC (All Aluminum Conductor), ACSS/TW (Aluminum Conductor Steel Supported), AAAC (All Aluminum Alloy Conductor) to name a few. There is, however, some controversy concerning them.
There are experts who contend that these conductors are no more than improved overhead conductors. Others say it’s all about cutting-edge material sciences improving modern conductors. FERC says it best, “Advanced conductors include present and future transmission line technologies whose power flow capacities exceed the power flow capacities of conventional aluminum conductor steel reinforced conductors,” and that seems adequate.
Dynamic Technologies
INL’s report stated, “A key characteristic of advanced conductors is their ability to withstand the high-conductor temperatures that occur when heavily loaded without excess thermal sag.” It also points out that reconductoring upgrades line performance at a much lower cost with less impact to communities than new construction and it’s much faster. This would be a good place to get an expert’s opinion on advanced conductors and all of the offshoots from this technological family tree. “Charging Ahead” contacted Daniel Berkowitz, Bekaert’s Strategic Market Manager to discuss this complex subject and get his viewpoint on advanced conductor technology and how familiar conductors like ACSR fit in the scheme of things.
Berkowitz began our discussion saying, “As you are aware, ACSR is a very generic term. The traditional ACSR/GA2 conductor is one with a standard zinc coating strength grade 2 steel core. It comes in various sizes and is great at being inexpensive and robust. This is what the grid is generally outfitted with. The advanced steel cores that we are developing can of course be used in either an ACSR or ACSS conductor. However, the conductor manufacturers tend to use the Bezinal (95% Zinc, 5% Aluminum) coating with a strength grade 5 steel core (sometimes referred to as “ultra”) in the ACSS/TW/MA5 conductor. Europe is already using even higher strength cores like strength grade 7 and 8 (“mega” and “giga” respectively). We achieve these strengths in part by adding more carbon content to the steel. This helps with the rated breaking strength of a conductor and allows the utility to string the conductor with more tension.”
Berkowitz explained, “One of the goals of the government’s transmission infrastructure modernization program is to add approximately 100,000 miles (160,935 km) in the next ten years or so. Given the problems with regulatory and permitting issues along with acquiring right-of-way, supply-chain issues, etc. that is a very ambitious goal. Reconductoring existing transmission lines, however, with advanced conductors can eliminate or shorten these concerns. Reconductoring utilizes the existing rights-of-way, and towers. Also, the majority of the other existing components are usable, all of which saves both time and money.”
Berkowitz continued, “Studies have been performed using a variety of advanced conductors replacing similar existing traditional conductors used on existing transmission lines. The results have been extremely positive. As an example, one case compared the replacement of an existing traditional ACSR conductor transmission line with an ACSS/TW (editor note - trapezoidal wire) advanced conductor. The ACSS/TW had a higher strength grade and an advanced metallic-coating. It was the same diameter as the original conductor. The results indicated the reconductored transmission line’s characteristics were improved and the capacity was increased by 218%. Tomorrow’s transmission grid has to have a higher efficiency than today’s system. Advanced conductors are one of the most cost effective and efficient tools in a utility’s toolbox.”
Holistic Approach
There’s an old folktale about how to eat an elephant. It says it’s done one bite at a time. That has to be the approach for adding or refurbishing 50 million miles (80 km) of transmission lines. Granted, building a new transmission line can be both time consuming and expensive, but it’s needed. And what about all the congested existing transmission lines? That has needs addressing too because new builds only go so far. Why not take a holistic approach?
In addition to new power lines, the reconductoring of existing transmission lines has to be included. It not only relieves the congestion, it provides a bigger bang for the buck! A high-performance, advanced conductor like the ACSS/TW discussed in the example above, increased the capacity of that existing line by 218%. That is the equivalent capacity of two transmission lines in one right-of-way. In most cases reconductoring costs less than a third of new line construction and it can usually be accomplished in months rather than years. If dynamic line rating technology is added we get an additional 30% to 40% capacity. Wire technology is a win/win for both the distribution and transmission grid along with the providers and customers!
