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

A transformer's or reactor's function and life expectancy are directly related to the temperatures that its components and structures experience. While temperature control schemes and data gathering activities may be employed in an effort to keep temperatures within favorable levels, 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 the document. 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, pumps are discussed, but only as far they effect temperature measurements. The temperature of the ultimate heatsink, 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. In order to ensure that auxiliaries such as fans and pumps are performing their temperature moderating functions properly, 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.