With the Green Deal from December 2019 and the Circular Economy Action Plan from March 2020, the EU strongly commits to improving both energy efficiency and material efficiency. In electrical applications it is not always apparent how a trade-off between these goals can be avoided. The sustainable peak load concept for public distribution transformers does exactly that: it is beneficial to transformer energy efficiency as well as material efficiency, with no need for compromise.
At the origin of the concept lies the fact that many public distribution transformers, as currently rated, are underexploited. This has historical antecedents. Stringent rules on loss reduction, compactness, and absence of toxic substances prompted various technological innovations, including the use of highly conductive material for the windings, magnetic steel with reduced losses, thermally upgraded paper as a solid insulation, and the use of natural ester as a liquid insulation. As a result, sustainable peak load transformers can withstand higher temperatures in the windings, and consequently higher peak demand, without compromising unit reliability or lifetime. This potential is usually not exploited.
In the sustainable peak load transformer concept, the unit complies with the energy performance requirements for a transformer of its size (e.g. requirements for a 400 kVA unit), but is allowed to be subject to temporary peak load values that are higher than usual (e.g. peak loads up to 540 kVA).
A group of experts conducted a modelling exercise to assess the impact of selecting sustainable peak load units for all transformer replacements in public distribution networks in the EU, with the following findings:
- The total annual energy losses of a sustainable peak load unit are similar to those of a conventional unit. This is due to the fact that the average loading in public distribution networks is low, resulting in a higher relative importance of no-load losses compared to load losses.
- The material savings potential of sustainable peak load transformers is substantial, with reductions in total weight of 11 - 15%.
- The purchase cost of a sustainable peak load transformer is comparable to that of a conventional transformer if all other parameters are kept the same.
Given these conclusions, widespread application of the sustainable peak load concept in EU public distribution networks is recommended. It would maximize both the energy efficiency and the material efficiency of public distribution transformers.
A major economic advantage of the sustainable peak load transformer is its compactness. Due to the transition away from fossil fuels, substantial growth in electricity consumption is expected in some sectors supplied by distribution networks. The sustainable peak load transformer provides the opportunity to upgrade transformer peak power while keeping the same unit dimensions, saving in installation costs. This will mean that such upgrades can be made at an earlier stage, making the distribution grid more robust.