Original scientific paper

Transformer Loading Capability vs Transformer Rating: Resolving a 100-year-old dilemma - Part I

Oleg Roizman

Abstract

Transformer Rating and Loading Capability are often treated as interchangeable, even though they describe two different things: an assigned limit and what a transformer can physically carry under specified conditions. The first part of this column looks back at the earliest transformer rating standards and loading guidance to show how the distinction emerged and why the terminology became blurred. It then follows the development of real-time thermal rating in overhead-line practice and compares how rating is understood for cables, overhead lines and transformers. Examples from PJM and EPRI show how calculated transformer loading capability can become an operating rating, or simply be erroneously labeled as one. The discussion will continue in the second part, to be published in an upcoming issue of Transformer Magazine. The proposed definitions of key terms are included in the upcoming issue.

Keywords

transformer rating; loading capability; dynamic rating; terminology; dynamic transformer ratings; rating methodology

Hrčak ID:

352437

URI

https://hrcak.srce.hr/352437

Publication date:

5.10.2026.

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