Low-Cost Robust Detection Method of Interturn Short-Circuit Fault for Distribution Transformer Based on ΔU-I Locus Characteristic

Winding interturn short-circuit (ISCF) fault is a common problem which occurs in distribution transformers due to multiple internal and external factors. Unfortunately, the variations in electric parameters under a slight fault are tiny and hardly used as effective characteristics for the detection and protection system. To address this issue, a low-cost robust detection method of ISCF based on the port voltage–current (ΔU-I) locus characteristic is presented in this paper. The mathematical model of the three-phase distribution transformer with ISCF is first established. Then, the ΔU-I locus function and relevant characteristic parameters are analyzed, respectively, which can reflect the healthy and faulty conditions. The axis length ratio between the major axis length and the minor axis length in the ΔU-I ellipse curve is defined as the fault indicator for the sensitivity and robustness of fault diagnosis. Moreover, this method can reduce the number of sensors and has strong robustness against load fluctuations. In the end, the theoretical analysis and simulation results verify the effectiveness of the ΔU-I locus characteristic.