Grid transmission lines are given static ratings based on maximum ampacity and temperature limits. The weather conditions used by regulators in these methods are typically constant values year-round or with seasonal patterns and are set using conservative assumptions for the conditions. By not accounting for additional cooling during periods of high wind or low ambient temperature, there is likely unused head room on many overhead transmission lines.  

Dynamic Line Rating (DLR) is a changing transmission line rating based on local conditions rather than a static rating assumption and provides additional ampacity capacity to a transmission line. The U.S. Department of Energy has identified DLR as a transmission and distribution infrastructure solution to defer upgrades, support line outages and increase yields of distributed power. DLR is one of many solutions known as Grid Enhancing Technologies. Idaho National Laboratory is leading research and analysis on industry hardware and software DLR solutions. The conservative nature of transmission line standards and the regional transmission operators can be hard to adjust, so research showing the benefits of DLR is important to prove the benefits of the method.

How Does DLR Work?

The ampacity of transmission lines is defined as the maximum amount of current the conductor can safely carry. It is necessary for transmission line operators to apply ampacity limits due to the thermal properties of the conductor. Dynamic Line Rating (DLR) is a technology and technique that uses the environmental conditions or a set of the conditions to calculate the ampacity of the conductor. The way the DLR is calculated has depended upon some amount of physical technology to implement the solution.


Conferences and Presentations

Computerized Wind Farm Generation.., Footprint Routing and Subsequent DLR

Transmission lines are the backbone of the U.S. electrical grid. Due to increased penetration of renewable resources, there is an increasing need for connecting the often-remote resources to existing transmission line infrastructure. To view presentation click here.

Using Dynamic Line Ratings for Wind Farm Gen-Tie Line Considerations

IEEE/CIGRE standards provide a base for overhead transmission line ratings.

  • Measurement of many types of sensors provide a possibility to provide more
    capacity as a time varying capability.
  • Wide Area Weather-based DLR can provide a calculation of the moment-to-moment steady state rating.

Forecasting Dynamic Line Rating with Spatial Variation Considerations​

Dynamic line rating (DLR) is a technology that allows the ampacity of an electrical conductor to be calculated using real-time or forecasted weather conditions.  To view presentation click here.

Sensitivity Effects of High Temperature Overhead Conductors to Line Rating Variables

For traditional overhead transmission lines, the maximum allowable conductor operating temperature on ASCR, AAC, or AAAC lines for determining the static line ratings can be quite low, typically well under 100 C. At these low temperatures, the primary driver for determining static line ratings are assumptions made about the wind speed and direction and the ambient temperature.


INL Media Contact

Abby Todd

Phone: 208-526-6166


INL Project Manager

Jake Gentle

Phone: 208-526-1753