Determination of temperatures in transformer windings

Measurements made immediately after shut-down of a transformer short-circuit temperature rise test contain information relating to winding temperatures and winding oil temperatures. These quantities cannot be measured directly in any practicable manner. As customarily made and analysed, the shut-down measurements may not be adequate for the purpose of revealing this information accurately enough to justify (for example) rating transformers by hot-spot winding temperature instead of average winding temperature. Details are given of improved methods of measurement and analysis which yield more reliable values of transformer thermal characteristics.