Transformer load losses cause various adverse effects, such as derating, a decreased lifetime, and greenhouse gas emissions. In this paper, the load losses caused by non-linear loads on distribution transformers are analyzed. For this study, the load loss expressions provided by the IEEE Standard C57.110 and ANSI/UL 1561-1562 were adapted to the usual case where the transformer currents differ in each phase. The novel load loss expressions adapted from the IEEE Standard C57.110 were applied using the software known as the “Transformer Loss Calculator” (TLC), implemented with LabVIEW. For the application of new load loss expressions, carbon dioxide (CO₂) emissions were determined by multiplying the load losses by the emission factors of each country. The experimental results are based on the recordings made by a FLUKE 435 Series II analyzer on the second of two 1000 kVA transformers, feeding real residential distribution networks with very differently distorted loads. An analysis of these transformers shows that the annual energy losses and CO₂ emissions obtained from the adapted load loss expressions could be more than 5% of those determined by the original IEEE and ANSI Standard expressions. Due to these percentage loss and emission differences, it is advisable to use the TLC software in transformer monitoring instruments.

Load losses determine transformers’ efficiency and life, which are limited by overheating and deterioration of their elements. Since these losses can be characterized by short-circuit resistances, in this article, we have developed expressions for the short-circuit resistances of three-phase transformers according to IEEE Standard C57.110. Imposing the condition that these resistances must cause load losses of the transformer, two types of short-circuit resistance have been established: (1) the effective resistance of each phase ($R_{cc,z}$) and (2) the effective short-circuit resistance of the transformer ($R_{cc,ef}$). The first is closely related to the power loss distribution within the transformer. The second is just a mathematical parameter. Applying these resistances to the 630 kVA oil-immersed distribution transformer of a residential network, we have concluded that both types of resistances determine the total load losses of the transformer. However, only $R_{cc,z}$ accurately provides the load losses in each phase. $R_{cc,ef}$ can give rise to errors more significant than 16% in calculating these losses, depending on imbalances in the harmonic currents.

Well-known industrial practice efficiency improvement techniques, such as reactive compensation, load balancing, and harmonic filtering, are used in this paper to reduce energy losses in distribution transformers, and therefore, to decrease carbon dioxide emissions and economic costs in the operation of these transformers. Load balancing is carried out by monitoring the values of the angles of the active and reactive components of the vector unbalanced power. Likewise, the application of Order 3/2020 of the Spanish National Markets and Competition Commission is described, in detail, for the calculation of the economic costs derived from the transformer energy losses caused by the load currents and the penalties due to transformer energy deliveries with capacitive power factors. Finally, all these improvement techniques are applied to determine savings in carbon dioxide emissions and costs on the electricity bill of an actual 1000 kVA distribution transformer that supplies a commercial and night-entertainment area. The results of this application case reveal that cost reductions due to energy loss savings are modest, but the reduction in carbon dioxide emissions and the savings in penalties for capacitive reactive supplies are significant.

The main objective is to propose a calculation method for assessing the benefits of individual domestic prosumers in self-consumption and economic savings when managing their own energy resources. The paper applies the demand-side management concept in the residential sector from the individual domestic perspective so that customers can understand the value of their own sustainable energy resources, conducting self-generation and demand management. The novelty lies in allowing the prosumer to manage their own energy resources to their benefit at a reasonable cost, instead of participating in automated large residential demand-side-management programmes that respond to the means of the grid system operator or other energy service companies, such as aggregators. A methodology for calculating the self-consumption rate and the economic benefit for the consumer is proposed, including three different cases: consumer demand is higher than self-generation, and consumer demand is equal to self-generation, and consumer demand is lower than self-generation. The methodology is validated with actual data from a household in Valencia (Spain) during a complete year, obtaining an average reduction in the annual electricity bill of 70% and a demand coverage with the self-renewable system reaching values of 80% throughout the year. The significance of this methodology goes beyond the economic revenue of the individual consumer; it also aims to guide consumers towards efficient practices in the use of their available energy resources and raise awareness on their energy behaviour.

A procedure for improving the energy, economic and environmental sustainability of the transformation houses in low-voltage distribution networks is described in this paper. This procedure is based on the reduction of the transformer consumption, copper and core losses. Likewise, the procedure distinguishes between transformation houses with old and new transformers. The reduction of core losses, replacing transformers with others of lower power or that are more efficient, achieves significant improvements in energy and environmental aspects. The reduction of copper losses, and applying reactive compensation techniques, such as harmonic filtering and load balancing, applied in old and new transformation houses, have a greater impact on cost savings, especially when there are capacitive consumptions, as the Circular 3/2020 of the National Markets and Competition Commission of Spain determines. The procedure has been applied to an industrial transformation house, which has an old 1600 kVA transformer, resulting in significant economic savings and CO₂ reductions of more than 60%, after replacing the current transformer with a more efficient one.