Determination of transformer board creep parameters under high-mechanical and thermal stresses

Abstract

During operation of a transformer, all components inside the transformer begin to age and lose their performances due to various stresses. Among these components, transformer boards (TB) used between windings have an important role in terms of equipment reliability for being used for both insulation and cooling purposes. TBs are exposed to all sorts of specified stresses during operation and their physical structure deteriorates by creeping over time. This deterioration leads to a decrease in the gap between winding turns, and insulation failures occur due to insufficient cooling. In order to prevent these types of failures, it is quite important to specify creep characteristics of TBs before the production particularly for high-mechanical and thermal stresses. In this study, creep parameters (secondary creep rate, time to breakdown) of TB samples used in a typical power transformer under various loading and temperature are determined experimentally. In addition, gradient values are calculated for fitted lines and results obtained evaluated in terms of transformer operating conditions. Creep data obtained under high temperature (90, 100 and 110 degrees C) and loading (30, 35 and 40 kg) makes an important contribution to literature and will help transformer manufacturers in design and production stages.