I think the large power transformer is not working as intended, or as it says in the in-game description of the item. To test this, I hooked an 8kW source with 400kJ of battery storage to 30 tepidizers.
A single large Power transformer limits the power to 3.84kW (4 tepidizers) in this configuration, most of the time. This implies the 4kJ of transformer storage gets used in 1 second.
One tick every 4 seconds, it outputs 25.92kW (27 tepidizers) - turns out 3 weren't covered so this is the max load. No line damage noted yet. If we can take the transformer energy reading at face value, this implies the energy is being used in 68 msec.
Btw there is no output_log file in OxygenNotIncluded_Data
Hook a load exceeding 20kW without batteries to a large power transformer using heavy watt wire and see what happens. Hook a load exceeding 2kW without batteries to a large power transformer using conductive wire and watch the wire melt (description says transformer prevents overloads but maybe they mean "prevents overloads on heavy watt wires" -- but even this is not correct as noted above).