Everything in this picture is brand new: the trains are a few months old, the high speed line is not yet open to commercial service (it will take one more year before it opens on September 22 1981). As of early Sept 1980, a first section located south of Montchanin has just got its catenaries fed with 25000 volts 50Hz. A huge one-year long series of real life testing can start as TGVs meet their race track for the first time. Over that decisive year, a TGV broke the old world speed record dating from 1955 (331 km/h), by reaching the then formidable speed of 380 km/h (on February 1981).
The reason why this area got electrified first is that it fares long 3.5% gradients, representing one of the key challenges that the French engineers decided to address head on. Cutting a high speed line straight across a hilly landscape with steep gradients would significantly cut the distance between Paris and Lyon and the construction budget. The high speed and high power of the trains would easily swallow such gradients… but would this work in reality?
Thus the engineers rushed to test the trains and the line in their most extreme configuration. On that day, 2 double trainsets (4 TGVs) ran on the steepest gradients, testing how the electric substation would fare. As part of these tests, a double TGV set stopped right in the middle of a 3.5% grade and started accelerating upward, while another double set was going downward, sending back electric bake power to the catenaries for the upward train. They also tested starting 4 TGVs simultaneously on the grade, right in front of the substation. These were truly pioneer times.