Service Life Estimation of Photovoltaic Plant Transformers under Non-Linear Loads

South Africa has achieved a substantial amount in the country's energy generation capacity through distributed photovoltaic systems. A much-discussed hindrance on this development has been related to the rich penetration of harmonics and distortion in the connected transformers, which drives a temperature rise and generation of hotspots in the active part components. In this paper, the loss components of a 15MVA transformer that governs its performance under non-linear loads are examined. Finite Element Method is used as a method to evaluate the transformer losses under these conditions. Subsequently, the generated hotspot temperature and remaining service life of the transformer are evaluated. In this paper, an effort is made to illustrate how a transformer manufacturer can predict the remaining service lifetime under various loads for solar photovoltaic application. Findings indicate that when the plant loading is gradually increasing during service, utility owners may contemplate replacing existing transformer with a higher MVA rating.