Co-ordination of Dry-Type Transformer Models with Transformer Geometry [includes discussion]

The present practice of using different temperature classes of insulation in a single unit as indicated feasible by functional test codes1 and evaluation of component insulations2 make the knowledge of temperature gradients throughout the dry-type transformer of prime importance. A number of thermal effects of presently used dry-type transformer geometries are evaluated and data presented showing their interrelation. Some representative ratios of hot-spot temperature rises are given allowing a closer co-ordination between a dry-type transformer aging model and its prototype. Since winding height is a major factor, some corrections factoring this item with the general ratios are proposed.