What’s A Macrogrid?

Source: Gene Wolf · T&D WORLD · | April 12, 2021

The term macrogrid may be more recognizable as the mega grid, or perhaps the hybrid grid: the configuration goes by many names.

Source: T&D World

And I thought 2020 was a weird year! So far 2021 is shaping up with its own brand of strangeness. I know it’s early in the year, but so far ERCOT’s rolling disaster gets my vote for bizarreness. I mean snow on Galveston Island,  5º in Houston, not to mention ERCOT’s power grid within minutes of collapsing. A collapsing grid really got everyone’s attention and started some discussing a national electric grid or rather the lack of one. A national grid has been discussed for many years, but only discussed.

There are three major power interconnections in the lower 48, but all of the focus lately has been on the ERCOT interconnection and its ability or lack of ability to transfer power in and out of ERCOT. Personally, I find it more surprising that there hasn’t been much discussion about the Eastern and Western Interconnections’ lack of power transfer between each other. Think about it, they’re also isolated, and much like ERCOT, that’s impacting their resilience, reliability, and performance. At least that’s what a growing number of experts are saying.  

These two NERC Interconnections represent roughly 950 gigawatts (GWs) of generation, but there is only about 1.3 GWs of transfer capacity between them. The transfer is provided by seven HVDC (high voltage direct current) back-to-back converter stations along an imaginary line that runs north to south from eastern Montana to west Texas. This imaginary line is called the “seam.” What got me thinking about this was an email I received from my old friend, Dale Osborn.

A Seamless Grid

Dale’s email brought me up to date on the National Renewable Energy Laboratory’s (NREL) Interconnections Seams study. Dale has been an advisor to NREL’s Seams project. The Seams study has been a massive effort involving regional grid operators, utilities, universities, and several national labs. Since I had built one of those converter stations along the seam, I have been interested in the project since its start.