Electrical transmission lines in a field next to a wind turbine.

New software—General Line Ampacity State Solver—resulted from an Idaho National Laboratory study of transmission lines and wind cooling. Photo by Dennis Schroeder, NREL 31732

A wind power plant study initiated in 2010 by Idaho National Laboratory (INL) and the Wind Energy Technologies Office sought to explore how transmission lines, when cooled by the wind, are capable of handling more electricity. The research resulted in the development of a new software tool: General Line Ampacity State Solver (GLASS), which offers the ability to blend data from weather monitors and electric utility systems with weather analysis algorithms enhanced by computational fluid dynamics (CFD).

Power transfer capacity is affected by stability, voltage limits, and thermal ratings, with the last representing the greatest opportunity to quickly, reliably, and economically improve the grid's capacity. INL's wind power team surmised that if they could come up with a reliable system for dynamic line rating to replace the conservative static line ratings in use, system planners and grid operators might have access to greater transmission capacity.

The first step was to find a CFD software program that could be integrated and tested against actual wind and weather station data. Coordinating with a CFD program from WindSim, the INL team developed GLASS.

Since 2010, INL has collaborated with Idaho Power Company on dynamic line rating concepts and recently finished a full instrumentation of two test beds with weather stations and line rating software in Idaho. INL also completed a cooperative research and development agreement with AltaLink LLC—Alberta, Canada's, largest regulated electric transmission company—on a field study of four transmission line segments in support of a wind project's expansion request.

"From what we've seen, it's working," said Phil Anderson, project leader for Idaho Power. "Our greatest challenge was to come up with a standard design that didn't cost a fortune." With GLASS, Idaho Power has been gathering weather data and calculating steady-state, transient, and what INL calls "true dynamic line rating" ampacities (ampacity is the amount of current a line can carry). The next step is ramping up the software to calculate forecasted line ampacities and temperatures. "It really shows the viability of weather-based dynamic line rating," Anderson said.

While WindSim was originally a software program designed to optimize placement and performance of wind turbines, the company's collaboration with INL has allowed the company to broaden its solutions, according to Catherine Meissner, WindSim's software development manager. "The next current challenge is de-risking the path to market and deployment," she said.

In 2018 and 2019, INL plans to refine the GLASS software with another industry partner, testing endurance and commercialization possibilities.