Proposal to Extend the Working Life of the M42 138/23.9 kV Transformer used in the Enelven Power System

The object of this work is to show the research developed due to the recurrent fault of one of the power transformer models of 42 MVA 138/23.9 kV (called for the purpose of this work M42), used in the ENELVEN distribution substations. The faults presented in this equipment are of very particular features, as it has not been possible to prevent faults in other types of the same model through the traditional predictive and preventive maintenance procedures. At the present time (April 2006) ten transformers have presented faults, attributed mainly to faults in the tertiary windings. The research proposes alternatives to prevent faults and to extend the useful life of this important equipment for the distribution system of Enelven. The proposals basically focus in reducing the short circuit levels to which the transformers are subjected and the possibility of eliminating the tertiary windings