Exploring Dynamic Line Ratings: Increasing the Capacity of the Grid

Electricity Canada: The Grid 2022

Richard Boulton

Director of Engineering and Technology, AltaLink

With Canada’s target to achieve Net Zero emissions by 2050, there is a push to incorporate more renewables onto the grid. The electrification of many of our current uses for fossil fuels, such as the switch to electric vehicles, will drive the need to move increasingly larger volumes of clean electricity through the grid. Many predict an increase in two to four times the amount of electricity used today.

As the Director of Engineering and Technology at AltaLink, I am working on preparing the grid for electrification and the integration of more renewables. One technology that we are currently exploring is Dynamic Line Ratings to help optimize the grid.

Overhead transmission lines are designed to operate up to a maximum operating temperature. Heat is generated by line losses which increase as more current flows through the transmission line. As this heat energy dissipates to the surrounding air, the amount of current needed to reach the line’s design temperature varies with ambient conditions. The two factors that have the most impact on capacity are wind and ambient temperature.

Exceeding a line’s maximum operating temperature can have safety implications and can jeopardize reliability, which is why utilities have rated the capacity of their lines using conservative assumptions of ambient conditions, referred to as ‘Static Ratings’.

Dynamic Line Ratings vary based on real-time measurements or forecasts of a transmission line or ambient conditions. Weather conditions are highly variable, and the static ratings are based on conservative assumptions. Most of the time, a transmission line’s capacity far exceeds its static rating, and can be as high as about double the static rating at times. AltaLink has tested various devices to measure real-time conditions on our transmission lines to produce dynamic line ratings. Alberta’s harsh environment caused these devices to stop working, go out of calibration or even be blown off the line. In the last few years, we’ve focused on meteorological approaches which utilize much more reliable weather stations and weather forecasts.

What we’ve found is that Dynamic Line Ratings are particularly well suited for lines whose loading correlates with ambient conditions, such as lines that move energy from wind generation. On windier days, when the wind farm is creating more power, the transmission line can move a higher volume of energy because it is being cooled. Basically, more wind creates a cooler transmission line, resulting in more transmission capacity.

AltaLink has successfully applied this technique to a transmission line attached to a wind farm, and we have been exploring other opportunities to apply this exciting and powerful new technology.

As the demand for energy transformation, electrification, and renewables continues to increase in Canada, Dynamic Line Ratings can help Canadian utilities unlock the capacity that already exists and transform the grid for the better. I’m proud of the work that we have done so far in piloting this innovative technology!