So, Chernobyl blew up during the course of an experiment to see if the steam turbine, spinning down, could still power the emergency core cooling system until the backup generators could pick up the slack (which took 60-75 seconds).
Obviously that failed, but there are still a number of RBMK reactors in operation, so I'm wondering if they tried again in a different reactor and found that yes, the steam turbine could do that? It seems like an important safety feature so I assume they must have tried again?
It was a design feature of the RBMK, it wasn't that it was some experimental new thing. The only reason it hadn't been conducted at Chernobyl before commissioning was because they wanted to complete the plant ahead of schedule.
It had also already been done 3 times at Chernobyl and always previously failed, so I presume it was something that required a lot of calibration and wasn't something they could just use a standard set of values for.