No Need to Compromise for Public Electricity Distribution 

With the ‘Fit for 55’ package and the Circular Economy Action Plan (CEAP), the EU is making a strong commitment to improving both energy and material efficiency. In electrical applications, it is not always apparent how a trade-off between these two goals can be avoided. The sustainable peak load concept for public distribution transformers does exactly that: it benefits both transformer energy efficiency and material efficiency, with no need for compromise.

At the origin of the sustainable peak load 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 have 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 natural esters as liquid insulation. As a result, transformers can now withstand higher temperatures in the windings, and consequently higher peak demand, without compromising unit reliability or lifetime. This potential is not usually exploited in order that losses are kept below the postulated value.

At low load levels, however, the relative importance of load losses diminishes, and the relative importance of no-load losses increases. As a result, choosing a smaller transformer for the same job has little influence on the total annual energy losses of the unit. The increase in load-losses during peak hours is balanced or exceeded by the permanent decline in no-load losses.

Public distribution networks will typically have such low load levels. Until recently, public distribution network loadings have been estimated only, not measured. With the introduction of smart meters, extensive measurement campaigns have now recorded full-year kWh data, which show that loadings tend to be lower than initially thought. The average load factors tend to be around 15% of nameplate capacity. Although this figure might initially seem low, it can be explained by the need for redundancy and reliability in public electricity networks.

Widespread application of the sustainable peak load concept in EU public distribution networks would maximize both the energy efficiency and the material efficiency of public distribution transformers.

This low load factor combined with the technical overload capacity leads directly to the concept of the sustainable peak load transformer. The ‘rated nameplate capacity’ will be the value by which the transformer will meet the energy performance regulations. The ‘sustainable peak capacity’ of the transformer will be set at a higher value. As long as the transformer operates in a network with low average loadings, as is the case in public distribution networks, allowing such a higher peak capacity will not increase the unit’s total annual energy losses.

A group of experts, under the European Copper Institute’s direction, 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.
• 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.

Based on these conclusions, widespread application of the sustainable peak load concept in EU public distribution networks 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. With 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. This is a critical aspect in urban environments with space restrictions and allows savings on installation costs. This will mean that such upgrades can be made at an earlier stage, making the distribution grid more robust.