# Distinction Between Interturn Short-Circuit Faults and Unbalanced Load in Transformers
## 5 Discussion  
According to the results obtained in this study, the mean value of the ISP and infrared thermography allow us to distinguish between small load imbalances and incipient inter-turn short-circuit faults in transformers. The experimental platform was implemented to reproduce intentional and controlled interturn short circuits without inducing imbalances through external resistances or removing turns to simulate the fault. The transformer bank used adequately represents the characteristic electrical behavior of three-phase transformers. This type of configuration allows for the reproduction of real phenomena such as load imbalances and incipient turn-to-turn faults under controlled and measurable conditions. While previous studies report interturn faults in transformers with severe short circuits affecting 20% to 60% of the winding, which can cause damage before being detected [14], other studies have used infrared thermography for short-circuit detection but relied on continuous temperature measurement, requiring continuous image analysis with a higher computational cost [10]. Additionally, some works focus on distinguishing incipient interturn short-circuit faults in rotating machines, where various sources of imbalance may exist [15]. This study demonstrates that incipient faults in a transformer can be detected from as little as 4.4% of the winding affected, corresponding to a two-turn short circuit, and that the  
Figure 16: Temperature increase rates according to the transformer condition. Figure 15: Infrared image of the modified transformer at full load, operating as a transformer with an incipient 4-turn short-circuit fault after 2 min of operation. change that this short circuit induces in the mean ISP signal of the three-phase currents is similar to that caused by a four-turn load imbalance, where the thermal effects are the key differentiating factor. A more severe fault, affecting 8.8% of the winding, is detectable using FFT analysis of the mean ISP, but, at this stage, the transformer is already experiencing the negative effects of a temperature increase rate of 26.7 \({}^{\circ}\)C per minute, whereas the four-turn load imbalance does not cause a significant temperature change compared to the healthy transformer. These results confirm that the mean value of the ISP and its spectral content are suitable indicators to capture the asymmetry and instability introduced by the fault. Additionally, the thermal image helps to confirm whether these electrical anomalies are due to the progressive development of a fault or to normal load conditions, thereby enhancing the diagnostic capabilities of the method. The ambient temperature and the cooling method of the transformers can influence the thermal evolution of an incipient short-circuit fault, but the appearance of the 2\(f\) component in the spectrum of the ISP mean value allows for the identification of the presence of a turn-to-turn short circuit, setting the basis for determining whether there is a significant temperature increase in the transformer. This complementarity between the electrical response and thermal behavior enhances the reliability of the detection, regardless of the transformer's thermal dissipation capacity. The effects of imbalances and short-circuit faults highlight the importance of implementing redundant fault detection, ensuring continuous monitoring for imbalance detection through the three-phase current signal and fault verification using infrared imaging to rule out or confirm an interturn short-circuit fault at an early stage. The ability to distinguish between incipient interturn short circuits and small imbalances contributes to diagnostic and preventive maintenance tools, enhancing the reliability of industrial and power distribution systems in electrical grids.