A novel high frequency voltage injection method for inter-turn short-circuit fault detection and location in electrical machines

This paper proposes a novel high frequency (HF) voltage injection method based on an analytical fault model in αand β-axis reference frame. Such method can predict the amplitudes of the HF α- and β-axis currents (iα and iβ) as well as how many turns are short-circuited, i.e., the fault severity. This could provide the theoretical support for designing the parameters of the injected HF voltages (amplitudes and frequency) and to improve the fault detection sensitivity. Different from other existing HF voltage injection methods in literature, the method in this paper can also detect which phase is faulty. This is because the developed analytical fault model can establish the relationship between the amplitudes of iα and iβ and the injected α- and β-axis voltages (vα and vβ) as well as the fault ratio. Based on this fault model, two sets of HF vα and vβ were injected in turn, i.e., the axis of vα was first aligned with the axis of phase A then aligned with phase B. The amplitude difference between the obtained iα and iβ can be used as fault indicator and can also locate the faulted phase. Furthermore, the variation of the fault current introduced by the injected voltages has also been analysed.