Determination and localisation of turn-to-turn fault in transformer winding using frequency response analysis

An incipient short-circuit fault does not cause a severe condition in the steady-state operation of transformers, but in transient conditions - the lightning or switching - it can result in an extended turn-to-turn short-circuit fault (TSCF) and eventually in transformer outage. This study aims to determine and localise small TSCFs using the frequency response analysis. For this purpose, an appropriate mathematical model is developed, which can accurately simulate the winding transient behaviour. Using this model, turn-to-turn short-circuit patterns are extracted for different turn-to-turn faults in the winding; then, the fault location is determined by comparing the measured faulty signal with mathematical short-circuit patterns. In this study, a heuristic index is proposed to identify small TSCF locations. The presented solutions are implemented on a real winding with a nominal rating of 1600kVA and a nominal voltage of 20/0.4kV.