maybe stick to oil filled basins rather then trying to use sealed tactical crap
IMO he is a victim of 'OIL BAD' 'POTTING GOOD' mentality.
You need to realize just because they made something that can be thrown into a wet damp manhole tunnel and installed by underpaid tossers (like literarly they will toss it) with zero plans for maintence does not make it good lab equipment as cool as it looks. Half this stuff is designed the way it is because its meant to be installed by the least possibly skilled worker in the fastest amount of time possible with zero maintence cost (and if you prevent maintence and require replacement then you gain money). it can be often done in a slightly more complicated way that requires some skills but brings major benefits to repairability and lack of explosions.
I cannot believe what you are saying. You simply don't know what that transformer is and what happened.
1) What happened is that this wannabe electrician connected the secondary as primary and overdrove it *continuously" by probably a factor of x5 over the nominal. Now let's change the whole industry and the standards so people like this don't get hurt LOL.
2) That transformer is made for measurements not for energy transmission. They are designed for low burden. They do not need heat dissipation. Epoxy is the most reliable, 0 maintenance, long lifetime solution. They can be installed horizontal or vertical. They are installed by the tens of thousands in medium voltage switchgear to measure voltage (along others to measure current).
Oil transformers have problems like risk of fires, humidity getting inside and can't be installed horizontally.
I'm just scratching the surface
And also that thing I bet was designed with the idea that its likely to go off in a isolated tunnel where no one is allowed to be if it is powered.
It is designed to be used with a fuse in the HV primary, so the secondary or primary never develop high pressures inside. Even if no fuses are used these transformers are very safe.
Phase-Phase instrument transformers are designed to withstand 20% more of the nominal continuously.
Even more, because a 3-phase system can have a ground fault and have ground shifted to a phase, phase-neutral instrument transformers could see the voltage increased by sqrt(3), so they are designed to withstand 90% more voltage as standard (thus the rating 1.9xUn/8h seen in many of these transformers)
In short: There is a lot of science and human thinking as to the why of these casted transformers, and there is
0 science and human thinking in what that "Youtuber" did