Design improvements in modern distribution transformers

Abstract

In the paper design improvements of distribution transformers related to improved energy efficiency and environmental awareness are discussed. Eco design of transformers, amorphous transformers, voltage regulated transformers and transformers filled with ester liquids are analyzed. As a consequence of growing energy efficiency importance, European Commission has adopted new regulation which defines maximum permissible levels of load and no-load losses of transformers with rated power ≤ 3150 kVA, and minimum peak efficiency index for transformers with rated power > 3150 kVA up to 40 MVA. The impact of new regulation on the design and economy of transformer is presented. Amorphous transformers, with up to 70 % lower no-load losses in comparison to the conventional transformers, could be an alternative with respect to energy efficiency. Although their initial price is higher than the price of conventional transformers, some studies show that they might have economic advantages. The increasing penetration of distributed energy sources can cause an increase in voltage variations in low voltage networks. To keep the voltage within limits defined by EN50160, voltage regulated distribution transformers could be used. Although mineral oil has been used as a dielectric fluid in transformers for many years, there are some environmentally friendlier alternatives – natural and synthetic ester-based fluids.