Dynamic Line Rating Tech Aims to Maximize Transmission Capacity

By leveraging existing transmission infrastructure, grid-enhancing technologies (GETs) like dynamic line rating (DLR) systems avoid costs that would otherwise be spent on building new transmission lines or roads with alternative routes for power flow. Still, GETs devices often lack independent testing covering costs, usage characteristics, economic benefits, and deployment and integration challenges. 

 

Transmission lines. Image used courtesy of Pexels/by PhotoMIX Company

 

Four projects will address this gap by testing innovations with nearly $8.4 million from the U.S. Department of Energy’s Grid-Enhancing Technologies (GETs) program. The recipients will demonstrate DLR technologies to optimize infrastructure in existing rights of way and improve power transfer to support a growing share of renewables on the grid. Some will also test power flow control devices, which push or pull power to balance overloaded lines with underutilized ones. 

 

What Is Dynamic Line Rating Technology? 

Transmission lines are typically given static ratings according to their temperature limits and maximum ampacity. This is often based on conservative assumptions. For example, operators may transmit only 800 MW on a system due to reliability margin reserves when the actual limit is 1,000 MW. Conventional ratings don’t consider additional cooling during high winds or cold temperatures, creating unused headroom on overhead transmission lines. 

 

Grids using DLR compared to grids with static ratings. Image used courtesy of DOE 

 

Power lines can deliver 50% more energy than their labeled limits on cold or windy days. DLR unlocks this opportunity by introducing a changing transmission line rating system informed by local conditions instead of the traditional static rating assumption. DLR hardware and software are designed to update the calculated thermal limits of existing transmission lines to determine new limits based on real-time power capacity. 

Dynamic rating of power lines uses the heat balance of an overhead conductor to design capacity limits. The maximum ampacity could depend on temperature, wind speed and direction, solar radiation, and location-based factors enabling additional ampacity for transmission lines. 

DLR can help ease congestion, where physical constraints reduce the power flow needed for reliable operation. Without sufficient transmission and distribution infrastructure to transport electricity from generators to load centers, generation may be dispatched sub-optimally. For instance, the maximum thermal limit of a transformer or power line conductor may restrict power flow, leading operators to reroute through sub-optimal paths and rely on conventional fossil fuels to meet demand. 

 

The benefits of grid-enhancing technologies. Image used courtesy of DOE (page 56)

 

GETs Projects Tackle Interconnection, Weather-based DLR, Offshore Wind Integration

Each of the four GETs projects will receive about $2.1 million. Georgia Tech Research Corporation will demonstrate and deploy advanced power flow control (APFC) and DLR systems supporting renewable interconnection and load electrification. The project will model and optimize multiple mechanisms to integrate these technologies with existing utility operations, providing system operators with field-validated implementation, deployment methods, and infrastructure resiliency metrics to integrate APFC and DLR in the future. 

Idaho-based Pitch Aeronautics will demonstrate overhead monitoring systems combined with weather-based DLR technologies—among the first real-world demos of its kind in the western U.S. The project aims to increase transmission capacity while reducing congestion costs and facilitating renewable interconnection to avoid curtailing power generation. The DLR demo will incorporate drones, transmission line sensors, computational fluid dynamics modeling, and ampacity forecasting. 

The University of Connecticut will demonstrate a DLR system in New England with changing weather and offshore wind integration. The project will install solar-powered DLR sensors along an existing 345 kV transmission line near the 800 MW Vineyard Wind project in Massachusetts, which is expected to come online by early 2024. The sensors will be placed at strategic points across 20.26 miles, collecting real-time information on conductor and ambient temperatures, line angle, and wind speed. These metrics can calculate the lines’ load-bearing capacity in any given condition. 

 

The first GE Haliade-X wind turbine was installed for Massachusetts’s Vineyard Wind project earlier this year. Image used courtesy of Avangrid

 

Another project, led by Nevada-based NV Energy, will focus on direct and indirect contact DLR technologies to increase transmission capacity and reduce congestion without reconductoring. Using digital twins, the company will assess power line capacity to make way for increased renewable transmission. It will also identify ideal sensor locations.