Harmonic Analysis of Inrush Current in Three-PhaseThree-limb Transformers Using Hartley Transform

This paper proposes a novel method to analyze inrushcurrent in three-phase three-limb transformers using Hartleytransform. Calculations for the time and frequency domain areconducted concurrently in this paper. The solution process ofthe differential equations is first simplified using operationalmatrices and the inrush problem is solved based on reiteration.Hartley transform is then used to study harmonic effects in thefrequency domain. This transform is a real valued function andconsequently gives results with the higher speed of calculations.In this paper, the method is applied to the analysis of inrushcurrent in three-limb transformers because of the flux couplinginteractions in multi-leg core structures. MATLAB code isdeveloped to simulate the time and frequency domainwaveforms with high accuracy and the results are helpful toevaluate transformer inrush current harmonic effects.