In power systems transients caused by energization of power transformers and voltage dip are some of the more common problems. Voltage recovery after a voltage dip can produce transformer saturation. This saturation produces an inrush current similar to that of the transformer energizing. In this paper transformer inrush current resulting by voltage dip is analyzed by using full period sliding window Discrete Fourier Transform. Saturable transformer and power system is modeled by STRI-SIMPOW simulation program. Simulation results are compared with test results that are obtained from SCOPMETER 199-C energy analyzer.