Decision Making Strategies to Establish the Replacement Priority of Transformers from Electric Distribution Substations

The paper presents a methodology used in the determination of the optimal replacement strategy of the aged transformers from the electric distribution substations (medium /low voltage) considering the Ecodesign European Directive. The methodology considers three objectives (energy-saving, power reserve, and average service availability), taking into account the weighting coefficients, having values between 0 and 1, depending on the choice of the Decision-Maker. Also, the methodology can be applied in other strategies based on the interchanging of the overloaded or underloaded transformers with different performance standards. The testing was done using a transformer fleet with 23 units from a rural distribution area belonging to a Romanian Distribution Network Operator. The optimal strategy, having the weighting coefficients equal with 0.7 for the energy-saving criterion and 0.3 for the power reserve criterion, led to an average energy-saving per transformer by 3.45 MWh/year and an average increase of the power reserve with 22.8 %, considering the same electricity supply continuity, whatever the replaced transformer.