IEEE Guide for Temperature Measurements for Liquid-Immersed Transformers and Reactors

Abstract

The function and life expectancy of a transformer or reactor are directly related to the temperatures experienced by its components and structures. While temperature control schemes and data-gathering activities may be employed in an effort to keep temperatures within favorable levels, the accurate and timely measurement of temperature must be achieved before any controls or gathering of data can be effective. At the center of a transformer’s thermal performance is winding temperature. It is the primary factor that drives thermal activity in every other structure and material in the transformer. Thus, this topic is well covered in this guide. Other structures, such as ties, taps, and bushings, do produce some local heat and are also topics that are discussed. Thermal modifying elements such as insulating liquid, fans, and pumps are discussed but only insofar as temperature measurements are affected by them. The temperature of the ultimate heat sink, typically air, water, or some other liquid, is particularly important, since the effective removal of the heat produced by the windings is predicated on efficient transfer of heat energy to a lower energy mass. To help ensure temperature-moderating functions are being properly performed by auxiliaries such as fans and pumps, measurements of motor temperatures or motor current are sometimes employed. All of these topics are discussed along with recommended equipment for and methods of making accurate and timely temperature measurements.