There are actually so-called “three phase combs” for the fuse panels: Sample Image. You put your fuses on a hat rail (in this case eight fuses, but those combs are available in different sizes), you stick that comb in from below and tighten up the screws. Then you connect the three phases to the connections on the left, or, in some fuse boxes, screw them right onto the bus bars.
Do they put a third of the panel on each phase?
Short answer: Yes.
There are actually so-called “three phase combs” for the fuse panels: Sample Image. You put your fuses on a hat rail (in this case eight fuses, but those combs are available in different sizes), you stick that comb in from below and tighten up the screws. Then you connect the three phases to the connections on the left, or, in some fuse boxes, screw them right onto the bus bars.
That is so clever! I hate working with high voltage but am still fascinated by it.