For the last decades significant technological developments in reduction of no load losses have been observed. They still account for about two thirds of total losses in distribution transformers. In the past this proportion was even higher reaching 80% share of no load losses in total losses. This proportion was however not even Europe-wide. In some countries or regions, because of changing load characteristics, situation might have been reversed.
Observing the cases of Poland and Czech Republic with former Czechoslovakia, applying gradually improved better grades of magnetic steel, technology of cut, decreasing laminations thickness led to reduction of these losses by factor of more than two during last 40 years. When comparing these losses with levels at the middle of the last century, the factor would be close to three. In case of load losses reduction, the evolution of improvements is less spectacular. Again cases of the same countries (PL and Cz) are considered.
Last five years show up that rated load losses have gone up quite significantly. This might indicate that users pay more attention to reduction of no load losses (and accept higher load losses in order to keep the transformer investment costs stable) which still account for usually more than two thirds of overall losses in transformers.
Based on these two countries and additional age profile of transformers in Poland we built the age – losses model. Although the model is based basically on two formerly Easter Block countries we believe it reflects the true situation in EU-25 as these countries have good transformer manufacturing tradition, the level of technical losses as well as age characteristics correspond well to EU averages. Furthermore population age distribution in Poland was only used for cross checking of population older than 30 years. Actually 2% yearly increase in [MVA] capacity and slightly progressive rate of replacement for aging transformers have been assumed.
We summed up percentages increasingly in figure below. This is clear now that for example replacing 10% of oldest (and presumably based on the model, least efficient) part of population will turn into replacement of units responsible for 21,5% of total no load losses and 15,2% of load losses. Similarly oldest 20% of population replacement will retract population responsible for almost 35% of total no load losses and about 30% of total load losses.
We must add that this model corresponds very well to SEEDT calculations. The age model specifies today no load losses at 69% of the average level while load losses at 89% of the average.