In recent years, as the federal government and states across the country continue to adopt ambitious zero-carbon targets for power supply, climate change continues to bring more severe and damaging weather, and customer energy demand continues to rise, one thing is for sure: enhancing our electric grid is non-negotiable.
Significant transmission infrastructure upgrades and investments are needed in the coming years to keep pace with rising electricity demand, electrification, and integrating the massive amounts of new clean energy sources slated to come online. A changing climate is also causing more severe storms and extremely challenging weather conditions that damage the aging infrastructure—and cause customer outages.
“At Eversource, we believe our future is clean energy, and a clean energy future starts with the grid,” said Eversource President of Transmission and Offshore Wind Projects Bill Quinlan. “At the same time, through the use of innovative equipment and software, we need to ensure that we are maximizing the transmission of electricity across our existing system as we continue to build out the clean energy grid of the future.”
Enter grid-enhancing technologies, or GETs. These are a wide range of technologies that include sensors, power flow control devices, advanced conductors, and analytical tools designed to improve electric system performance and benefit customers.
Eversource has extensive experience with GETs. In some cases, Eversource’s standard equipment is GETs, and this means that the vast majority of projects result in significant additional capacity to existing infrastructure. The company has been studying and utilizing these technologies on its transmission system for decades—some as far back as the 1980s. As part of Eversource’s solution-development process and analysis of alternatives, it evaluates GETs and conducts a thorough cost-benefit analysis on behalf of its customers before implementing the technology or software.
On average, projects over the last few years to rebuild transmission lines to replace aging infrastructure have increased individual line ratings by 200% to 300%. This is because Eversource uses modern high-temperature, low-sag advanced conductors, which is the company’s standard conductor of choice. Without use of this technology, two or three new additional transmission lines would need to be built along the same corridor for each rebuild project to achieve the same increase in capacity. Not only do these line rebuilds utilize more resilient structures that can withstand higher winds and environmental damage, but the lines’ increased capacity can be used for a myriad of purposes—as one example, interconnecting a new solar generator, which can contribute significant property taxes and other local economic benefits.
Another GETs example is Eversource’s successful commissioning and placing into service the world’s first grid-forming static synchronous compensator, or STATCOM, which is a reactive compensation device capable of quickly providing or absorbing reactive current. This technology enables the safe and reliable operation of South Fork Wind, the country’s first commercial-scale offshore wind farm that saw its turbines marshaled out of New London’s State Pier.
STATCOM is being used on the South Fork Wind project.
Credit: Courtesy of Eversource
This type of specialized STATCOM uses inverters capable of “grid-forming” control. This emerging and promising technology offers numerous advantages in specific applications, such as the inherent capability to create and maintain voltage stability during unbalanced faults and extremely weak grid conditions. Most inverter-based resources utilize “grid-following” inverters, which depend on the grid to provide stable voltage and frequency reference. Tremendous industry research and study are being poured into the benefits and capabilities of grid-forming inverters. Eversource has published technical papers in journals and given talks internationally on its best practices and lessons learned from utilizing this cutting-edge technology.
Array cable installation at the South Fork Wind substation.
GETs can also be utilized to help achieve carbon-reduction goals in many ways. For example, “clean air” circuit breakers use purified oxygen instead of SF6—a potent greenhouse gas—as the insulating medium. In December 2022, Eversource energized the first 115 kV clean air breaker in the United States as part of a suite of upgrades to a substation in Preston. In December 2023, Eversource also energized the world’s first 345 kV clean air breaker at a substation in Haddam Neck. These breakers are important safety devices that help protect the system from damage by an overcurrent while increasing the reliability of the system and lowering carbon emissions.
Eversource, in collaboration with the University of Connecticut (UConn), was selected as one of four grant recipients through a federal Department of Energy program to develop technologies that improve grid reliability, optimize electricity infrastructure, and facilitate grid connection with renewable resources. One of the ways Eversource is collaborating with UConn on GETs is to deploy new solar-powered dynamic line rating, or DLR, sensors along existing transmission lines in Massachusetts that are critical to integrating and delivering new offshore wind power.
DLRs help determine conductor thermal ratings more dynamically using improved, more granular, or real-time data. This is especially helpful when a large amount of power—like an offshore wind farm—is interconnected to the electric grid, and system operators need to determine the prevailing current-carrying capacity limits of transmission lines. As more offshore wind projects come online over the next decade to help meet Connecticut’s decarbonization and clean energy goals, Eversource can take lessons learned from this critical research to ensure DLRs are implemented efficiently and the benefits are maximized.
In partnership with the University of Connecticut, Eversource plans to install non-contact DLR sensors on an existing 345 kV transmission line between two substations which will allow for the optimization of the nearby 800 MW Vineyard Wind offshore wind farm.
Credit: Courtesy of Eversource
“GETs allow us to maximize the utilization of existing facilities; plan for the grid of the future; more efficiently integrate new sources of clean, renewable energy into our electric grid; and bolster resiliency and reliability for our customers,” said Eversource Director of Transmission System Planning Jacob Lucas. “While GETs are an important component of the modernized electric grid that complements clean energy projects, they are not a one-size-fits-all solution and must be carefully evaluated on a case-by-case basis. Our ultimate responsibility is to provide our customers with safe and reliable electric service—cost-effectively.”