Huge blue thing

According to the dimensions of the machine transformer of unit EC 3 these men look rather small...
This is a 440 MVA, 23 KV / 230 KV transformer, equipped with a forced cooling with special oil.
The casing is filled with oil and the blue drum on top (in the back) is used as an expansion drum.
Here Bob and Arjan (trainee) are looking at the oilpressure in the cables (red) which lead to the substation.
Maybe more explanation tomorrow.
Have a good night/day!