Doesn't this excerpt sound like some planning could help (move sensitive units farther apart)
The description of the transformer sounds like one of the main transformers since it’s located so close to the turbine hall (non-nuclear) portion of the plant. The transformers are filled with a flammable coolant. The transformers sit on a foundation that is inside of a concrete pit. The purpose of the pit is to contain the cooling fluid if a leak develops in the transformer.
It’s not unusual for the coolant to catch fire if it leaks out since it may be associated with a transformer that overheats.
The burning oil explains why there was black smoke. The transformers are connected to the generator by what most people would think was large aluminum pipe. For design reasons you do not want the transformers a long way from the turbine hall.
No, those transformers at ALL power stations are set by very, very strict electric volt-distance requirements between the heavy cables. All such transformers are built the same way - at nukes as at gas turbines or coal or the old oil-fired plants. You just don’t hear about a non-nuke transformer problem.
Terrorists DID shoot up a nuke transformer a few months ago. That attack (by multiple armed men, all well coordinated was promptly shut up in the news - but no one has been found responsible. No group has been publicized as claiming responsibility either! To me, it sounds like a test assault. Oboma can’t allow more terrorist attacks in the US, can he?)
One of the most serious things that can happen at a nuclear power plant is to lose the grid. The reactors put out energy at a tremendous rate, often over a hundred million horsepower. That energy supply can’t be turned off instantly. If the grid is lost, the energy has to go somewhere else, almost instantly. This makes the shut down process critical.