Analysis of winding inter-turn fault in transformer: A review and transformer models

Transformers have emerged as an integrated part of a power system. Any fault in the transformer can cause a severe outage, which therefore necessitates continuous monitoring and diagnostics of its operation. The renewed thrust in smart power system networks along with the development of advanced methods in the monitoring and diagnostics has resulted in major impetus to research in the related domain. Among the detection of various faults in the transformer (or in any electrical machine in general), detection of winding inter-turn fault is critical since its effect is not easily comprehendible at lower magnitude in the signatures of terminal voltages and currents. Several techniques have been reported in the literature for detecting this fault. This paper reviews and compares the diagnostics methods based on their advantages and limitations. This highlights a further scope in the monitoring and diagnostic of the winding inter-turn fault. Finally, simple analytical models of three- and five-legged transformers are developed based on their electrical and magnetic equivalent circuits, which can be easily implemented in the analysis of winding inter-turn fault. Various results obtained from the analytical models are validated with the help of Finite Element (FE) modeling using ANSYS Parametric Design Language (APDL).