Transformers Fleet Management Through the use of an Advanced Health Index

Power transformers represent the highest value of the equipment installed in transmission substations, comprising up the 60% of the total investment. They are expected to operate for several decades without faults and possibly without relevant unscheduled maintenance practice. The new approach is developed for reducing time based maintenance and, increasing condition based maintenance and to introduce predictive maintenance as well. The aim of predictive maintenance is first to predict when transformer failure might occur, and secondly, to prevent occurrence of the failure by performing maintenance. Diagnostic information can be evaluated individually or better by a complex algorithm which merges all the single inputs and their Rate of Increase (RoI) creating a mono-dimensional figure called Health Index (HI). This concept represents a real ‘shifting of paradigm’, as it deeply affects the criteria for transformers grid management and selection of the electrical utilities and grid companies.