PT fuse is a voltage transformer.

Voltage transformers and transformers are very similar, both used to transform voltage on a line. Transformers transform voltage to transmit electrical energy, so their capacity is large, typically measured in kilovolt-amperes or megaamperes. Voltage transformers transform voltage primarily to power measurement and relay protection devices, measure line voltage, charge, and energy, and protect valuable equipment, motors, and transformers in the event of a line fault. Therefore, voltage transformers typically have a capacity of only a few volt-amperes or tens of volt-amperes, with a maximum capacity of no more than one kilovolt-ampere.

The primary and secondary sides of the generator outlet are connected to insurance, that is, fuses. Their function is to melt when a fault occurs inside the PT and isolate the fault point system. The primary side of the generator PT is connected to insurance, and the secondary side is now mostly the air side, which is used to replace the insurance.