Finite Element Modeling and DWT Analysis of Power Transformer Interturn Faults

As one of the most common types of faults inside transformers, interturn short-circuit faults seriously threaten the safe operation of the bulk power grid. In this digest, power transformer interturn faults were investigated by coupling the transformer finite element model and the external circuits. As typical fault cases, interturn faults inside a three-phase two-winding power transformer were simulated, and discrete wavelet transforms was adopted accordingly to extract the characteristics of the terminal currents. The results show that the wavelet coefficients exhibited significant differences between normal operation and interturn short-circuit faults. Due to the nonlinear characteristics of arc in insulation oil, periodic spikes appear in the detail signal, corresponding to the zero crossing of arc current.