Abstract: The inter turn short circuit of the voltage transformer on the outlet side of the generator can cause equipment damage, thereby threatening the reliable operation of the generators. In order to explore non-invasive detection methods for early inter turn short circuits, this paper conducted experimental research on the circulating current characteristics and leakage magnetic characteristics of short-circuit turns during inter turn short circuits, and carried out magnetic field simulation analysis during inter turn short circuits. As a result, it was found that the short-circuit current reached ampere level when a turn to turn short circuit occurred, leading to a significant increase in the leakage flux of the iron core. By detecting changes in the leakage magnetic field, it is not only possible to diagnose early inter turn short circuits in PT, but also to locate faults based on the value of the leakage magnetic field at different locations.