Application guidelines for dry-type distribution power transformers

A large number of distribution transformers, currently utilized in low voltage (LV) power systems are of dry-type design. This includes, the IEEE Class II ventilated dry-type design with 3-phase kVA ratings in the approximate range of 500 kVA - 2.5 MVA and primary voltage ratings ranging from 4.16 kV to 34.5 kV and the secondary voltage ratings of 600 V and below. This paper presents a comprehensive review of dry-type transformers design and provides some application guidelines including insulation system characteristics; BIL; losses, overloading, and loss-of life; and price.