Dry-Type Single-Phase Overhead Distribution Transformer

This paper describes the concept and development of single-phase pole-mounted dry-type transformers for overhead distribution system, named CAREPOLE®. The rating is in the range of 10 to 100 kVA and primary voltage up to 36 kV. A tap panel with up to 5 different voltages is provided on the top of the HV bushing. The efficiency is compliant with the DOE/2016 regulation in a compact design, having the similar mounting structure as the liquid-immersed transformers. Electrical insulation is fully solid, using a cycloaliphatic resin which has a high capacity to withstand extreme outdoor environments and ensures that CAREPOLE® has a high capacity to withstand short-circuit events. The most important elements of the design of the transformer such as electrical field, casting gelation and temperature rise, were analyzed using finite and boundary element simulation tools.