KBR Magneto applies polyurethane resin as dilatation layer on cores of medium voltage transformers. In the DiLaTech technology the core, the voltage coil and the band are covered with a monolithic dilatation layer in one manufacturing cycle in a closed type form. The operation is carried out directly at the instrument transformer manufacturer’s place. It allows automation of the production process and reduces costs. The cores with DL and DiLaTech dilatation have good, repeatable magnetic properties and guarantee the required degree of accuracy without additional operations compensating the amplitude error.