Dynamic Line Rating might not be something that gets discussed around the dinner tables of America, but it could play a significant role in keeping the lights on and affordable.

Close to 70 people from the U.S. Department of Energy and the electrical utility industry came to Idaho Falls for a Dynamic Line Rating (DLR) workshop hosted Nov. 7-9 by Idaho National Laboratory. The workshop also provided a backdrop for the launch of a new industry group focused on upgrading the nation’s transmission network.


At issue was how to integrate new ideas and techniques into a grid that is changing for a number of reasons.

Wind power and other renewables, combined with changing consumption patterns and smart grid management, have opened up new possibilities to grid operators. In the past, transmission and distribution networks have been operated in a conservative fashion, resulting in a typical usage rate lower than the maximum transmission capacity. The more electric current a line carries, the hotter it gets and the more it sags. After a certain point, a line operator cannot add additional current without overheating and damaging the line. Planning has involved worst-case scenarios and static line ratings.

Taking wind and weather conditions into account, along with solid modeling and control approaches, DLR has shown potential to unlock latent network transmission capacity – a welcome development, as it typically takes five to 10 years to bring new transmission from the planning stage to construction and operation, costing millions of dollars of investment per mile.

To use dynamic line ratings, engineers need accurate real-time information about wind conditions and factors such as the line’s temperature and amount of current it’s carrying. That information then needs to be conveyed to utility operators in a way that enables them to quickly and safely adjust generation to meet load demands while operating within transmission safety limits.


Along with all the discussions of ampacity (the maximum amount of current a line can safely handle) and load at the INL workshop, financial considerations were never far from the presentations and panel discussions. For a utility to invest in new hardware and software, it has to make financial sense, said Mark Lancaster of Southwire, a large wire and cable manufacturer based in Carrollton, Georgia. “Utilities exist to make money for shareholders,” he said.

Cost, practicality and maintainability are the major factors in any line enhancement or upgrade, said Dave Angell of Idaho Power Co. Planning has to be long range. “Two years from now is already in the past,” he said. And rate pressure from customers and public utility regulators is always top of mind.

In addition to enhancing transmission line capacity, DLR has the potential to boost grid reliability and resiliency, said Charlton Clark, program manager for grid integration in DOE’s Wind Energy Technologies Office. While the concept has been around a long time, new developments in the speed of computation and communication have made DLR more feasible. Whether it’s incorporated into existing infrastructure or integrated into new transmission lines, “It’s a very inexpensive insurance policy,” he said.

Idaho Power has been working on DLR solutions with INL for nine years, and the utility now has roughly 450 miles of transmission line in two test beds set up to provide real-time weather information. This has been integrated with INL-developed software called General Line Ampacity State Solver (GLASS), a finalist for a 2017 R&D 100 Award.

The Java-based GLASS software dates back to around 2010, when INL researchers studying wind power plants noticed that transmission lines being cooled by the wind seemed able to handle more load. Using a commercial computational fluid dynamics (CFD) program, the team blended data from commercially available weather monitors and electric utility load data with CFD-enhanced weather analysis algorithms.

The commercial program developed by WindSim, a Norwegian company, was originally designed to optimize placement of wind turbines. While WindSim’s collaboration with INL has allowed the company to broaden its solutions, the current challenge is “de-risking the path to market and deployment,” said Catherine Meissner, the company’s software development manager and a panelist at the DLR workshop.


The biggest challenge could be creating vision in the industry, Southwire’s Lancaster said. “(Without) that, there is no market for DLR equipment. You really need a product line and help educating utilities. The value is not in how much or even what you know, but in how you use it.”

The INL-hosted workshop also provided the occasion to launch Working for Advanced Transmission Technology (WATT), a coalition of representatives from technology companies that have developed tools and processes to make the grid more reliable, flexible and cost-effective.

“The question is whether we can put the right incentives in place so that utilities who deploy them will share in the rewards,” said Todd Ryan, director of regulatory affairs at Smart Wires and chairman of the coalition. WATT’s goal is to promote the deployment of advanced power flow control, dynamic line ratings, topology optimization and other technologies with the potential to deliver more energy to customers over existing grids.

“We’ve been encouraged by the support from regulators, grid operators and transmission owners,” said Hudson Gilmer, vice president of Genscape and the coalition’s chair-elect. “We see an important role for WATT to engage these groups and inform them about the compelling benefits of advanced transmission technologies.”

Posted Dec. 6, 2017