Life estimation of distribution transformers considering axial fatigue in loose winding conductors

This paper presents an experimental study on axial fatigue behaviour of loose winding conductors of aluminum and copper wound distribution transformers. Algorithms are presented for estimating the life and switchings withstand capability of distribution transformers by considering axial fatigue in loose winding conductors. The life and switchings withstand capability of distribution transformers have been calculated by using experimentally determined results of fatigue life cycles of winding conductors corresponding to stress. The experiments were conducted considering wire sizes and other parameters of 25 kVA distribution transformers. The outcomes of this study can be used as a guide for designing and producing reliable distribution transformers by selecting suitable conductor diameter which may has better fatigue life cycles endurance capability. This study is useful especially for frequently energized distribution transformers having insignificant protection against cold load pick up and inrush current.