Gene Wolf
Thyristor-controlled series capacitor.
Thyristor-controlled series capacitor.
Thyristor-controlled series capacitor.
Thyristor-controlled series capacitor.
Thyristor-controlled series capacitor.

The Impossible Takes Longer

Dec. 5, 2023
With all the renewable generation being added to the power grid, there is an increasing need for more transmission capacity.

With 2023 in its final month, there is a great deal of speculation about 2024! What will the new year have instore for the power delivery system? Reading all the predictions, prophecies, and forecasts presents some interesting ideas. In one way or another they all seem to be focusing on the transmission system. That’s probably because there are over 2,000 gigawatts of renewable generation waiting to be connected the grid.

According to all the reports, this power is being held up by interconnections queues, permitting, supply chain issues, and the condition of the transmission system itself. So it’s a reasonable assumption that addressing transmission bottlenecks will become a higher priority in 2024. It’s also a good bet we’ll be hearing a lot about the technologies that can squeeze more megawatts out of the existing transmission system and can add gigawatts of capacity to the entire power grid. 

Technology to the Rescue

There’s an old saying, “The difficult we do now, the impossible takes a little longer!” That could be the mantra of today’s amazing new technologies and non-wire alternatives when it comes to addressing the power grid’s challenges. What we are talking about are the grid-enhancing technologies (GETs). They have been the subject of numerous publications this past year. Let’s look deeper into GETs and get a better understanding of what they are.

Last year, the Department of Energy (DOE) issued a report specifically about GETs titled, “Grid-Enhancing Technologies: A Case Study on Ratepayer Impact.” That report looked at the effects of GETs within existing transmission lines and on the customers. It was followed by DOE’s draft report titled. “National Transmission Study,” which focused on the challenges of an aging infrastructure. Taken together these two publications provide some insightful reading about the transmission systems needs and how to address them. They can be downloaded from the DOE’s website for anyone interested.

What are GETs anyway? There are several definitions, but the most common is “Hardware and software that increases the capacity, efficiency, and/or reliability of the transmission grid.” That covers a wide bandwidth when it comes to digital technologies used in the smart grid. Some authorities add that GETs provide operational support while larger upgrades are completed, but that gives the wrong impression.

These are not stopgap measures to be removed once legacy technologies have caught up with the transmission grid needs. GETs are proven applications that allow the difficult to be done right now!

They fall into two separate categories when it comes to classifying them. One type of GET are installed quickly for achieving fast results straightaway. The other type of GETs take more time for deployment, but that’s because they are more complicated. The complexity, however, comes with paybacks that can’t be matched by traditional methods used in conventional transmission lines. These are the applications that allow us to move into what was once considered the province of the impossible, and like the saying goes – that takes a little longer. 

Fast-Tracked GETs

One of the exciting aspects of fast-tracked GETs is how quickly they can be installed and start working. These are fast-paced projects that get results immediately, but are receiving pushback from those unfamiliar with the science involved. A great example of this is the dynamic line rating (DLR) technology. Many operators are seeing from 25% to 30%  or more of unused capacity in existing transmission lines using the DLR technology.

DLR technology is basically a system utilizing hardware installed on the transmission line to gather real-time operational and environmental data. All of the real-time data is collected and analyzed by sophisticated software, which is then combine with a 3D (3-dimensional) digital twin of the transmission line. The virtual transmission line model uses the data to optimize the loadings of physical transmission line in real-time.

DLR technology has proven itself over several decades of use throughout the world. FERC’s (Federal Energy Regulatory Commission) Rule 881 requires transmission providers to implement ambient-adjusted transmission line ratings, which is a boost for DLR technologies. FERC has pointed out that transmission grid congestion would be greatly reduced if utilities/transmission operators were able to tap into this capacity in their existing transmission lines that goes unused today. 

Trailblazing GETs

The complex GETs require more time to accomplish their goals, but their results are amazing once operational. A good example would be the FACTS (flexible alternating current transmission system) controllers found in the power electronics family. These devices can shift the flow of power over the transmission system and balance overloaded transmission lines. They include series controllers like the thyristor controlled series capacitors. There are also shunt connected controllers like the STATCOMs (static synchronous compensators) and SVCs (static VAR compensators). In addition, there are combinations of series-shunt controllers like the UPFCs (unified power flow controllers).

Another branch of the power electronics family is HVDC (high-voltage direct current) transmission using VSC (voltage source converter) technology, which is like having a GET on steroids. HVDC-VSC has become the go to technology for developers needing transmission lines capable of moving extremely large blocks of renewable generated power to market. They’re flexible and have the ability to push clean power to exactly where it’s needed. This past year saw “Charging Ahead” explore several of these HVDC-VSC transmission technologies illustrating its adaptabilities.

The first story demonstrated HVDC-VSC’s ability to adapt to the available rights-of-way with “Rethinking Transmission ROW” (for details see www.tdworld.com/overhead-transmission/article/21255605/rethinking-transmission-row). A few months later there was "Transmission Lines With A Different Twist” (for details see www.tdworld.com/overhead-transmission/article/21268392/transmission-lines-with-a-different-twist). It showcased HVDC-VSC’s ability to moved massive blocks of power over extremely long distances. The last article was "Superhighways Are Supercharging The Transmission Grid” (for details see www.tdworld.com/transmission-reliability/article/21272798/superhighways-are-supercharging-the-transmission-grid). It featured moving gigawatts of offshore power to market across national borders to load centers far removed from the generation sites. 

Moving out of the digital realm, there are some wire-based GETs that are attracting attention. These are the advanced conductors made of modern composite cores and low resistance aluminum wire. They are more efficient than legacy conductors. In addition, they sag less, and have higher power capacities.

These conductors can be used in new construction, but it’s the reconductoring of existing lines that is generating excitement with designers. Reconductoring is simpler permitting wise. It also costs less and it’s faster to accomplish. Some conductors like ACCC (aluminum conductor composite core) can carry 2 to three times the amount of power compared to ACSR (aluminum conductor steel reinforced) cables. 

There's a Third Type

Just when you think a technology fits neatly into a well-defined box, an exception pops up. Grouping GETs into fast-track and slower deployment projects is convenient, but there is a problem. Some GETs start out in the fast-track class, but what happens as their application matures? The fast-track GET becomes more complex and its deployment times lengthen until they are no longer fast-track. Several types of GETs fit into this exception area.

Solar-plus-storage turned microgrid exist as both fast-track and slower deployment GETs. Rooftop solar plus storage leads the pack when in fast-tracking, but when electronics are added they can become microgrids. Many commercial and industrial users have opted for the microgrid option with added capacity to meet their needs. Others found microgrids could be combined making community microgrids. That has matured into neighborhood and town microgrids sized to meet their power needs. It didn’t take long for them grow in scale and move to the utility’s side of the meter.

In this role, they require more time to design, procure, and install. Still, they are one of the fastest ways to provide resiliency and reliability. Utilities are also using large-scale microgrids to replace or delay needed additional transmission and/or distribution lines. Duke Energy found a microgrid was more flexible than building a second feeder to a remote community in their service area (see “Microgridation Is Changing The Power Grid”  https://tdworld.com/21271684 for details).

Last summer, the DOE said the U.S. needs to expand its transmission capacity 60% by 2030 to meet its clean energy goals. With over 642,000 miles (1,033,199 km) of high-voltage transmission lines, that’s more than 385,200 miles (620,000 km) in the next six year. According to JP Morgan transmission growth has only been about 1% over the last five years, and that doesn’t include the amount of distribution circuits that must be added.

Adding thousands of miles of new transmission and distribution lines is an impossible challenge using traditional approaches for adding to the transmission system. Fast-track GETs can make the difficult happen right away! DRL technologies can add 25% to 30% or more of transmission capacity to the transmission system quickly. Granted that’s not the 60% capacity DOE said was needed, but it’s about half of the goal and it can happen faster than six years with only one of the available GETs. The impossible can be done with GETs, but it does take a little longer!

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