Technical and economic analysis of copper utilization on new windings of repaired distribution transformers originally designed for aluminum

This paper aims to analyze, technically and economically, the benefits of the copper utilization on new windings of repaired distribution transformers, originally designed for aluminum. Three commercial single-phase distribution transformers commonly installed on urban and countryside areas of Brazil were submitted to routine tests and temperature rise test. All the tests were performed at LAT-EFEI- High Voltage Laboratory in accordance to Brazilian standards and the Brazilian Labeling Program (PBE) for oil-immersed distribution transformers. The technical evaluation compares the losses before and after the repair process and the temperature rise test results of the repaired transformers. The economic analysis is based on load losses and no-load losses capitalization along the equipment useful lifetime and compares the investment in a repaired level C transformer, made with copper, against level E transformer, made with aluminum, providing the net present value and the investment payback time.