Power Standards Lab is deploying instruments to observe the effects of the August 21 solar eclipse on the electric power grid.

The eclipse will pass through the two largest North American power grids: the Western Interconnect and the Eastern Interconnect. (Read "How the Solar Eclipse Will Impact U.S. Power Production.")

The lab says that grid operators will balance the output of thousands of grid-connected generators against all the rapidly varying grid-connected loads. It says this balancing is eased by two characteristics of grid load called "diversity" and "predictability."

The eclipse will challenge both the diversity and predictability of a significant amount of solar power generation. The eclipse will darken a large number of solar power generators simultaneously, reducing diversity. Grid operators know where their large solar arrays are and how much power they generate. But they have far less information about smaller rooftop solar arrays.

And that's what makes this experiment interesting, the lab says.

Instruments will watch the grid frequency, which indicates the balance between generation and load. In normal operating conditions, it should be 60 cycles per second, or 60 Hertz. Higher than 60.000 Hertz means there's slightly more generation than load; lower, and there's slightly less. The grid operators adjust generator settings to maintain a steady flow of power.

Watch this experiment unfold, live, at two websites: LiveEclipse.PQube3.com/west and LiveEclipse.PQube3.com/east.

Power Standards Lab is a privately held company in Alameda, Calif., that performs research projects with the U.S. Department of Energy and the National Labs.