Experimental Validation of a CORE Type Power Transformer

Abstract

The current paper presents the validation of a finite element (FEM) design methodology for a CORE type power transformer. Any new methodology can only be implemented when it generates significant added value. The application of FEM to the design of power transformers leads to lighter, more balanced mechanical structures that are more economical to manufacture. To be sure that the methodology is a good predictor of the stress and strain effectively encountered by the power transformer, it is necessary to measure stress and strain during loading and compare those measurement values with the original FEM predictions. The current paper begins by first presenting the FEM predictions for a CORE type power transformer. Secondly, by means of extensometry, the strains induced in the tank during loading were measured and the stresses present in the tank were estimated from basic stress-strain relationships. The feedback given by the strain measurements served as a validation tool for the FEM design predictions.

Evaluation of different types of steel under high loading rates for short circuit applications

“…In general, the structural parts of power transformers are made from non-alloy structural steel types but the selection process of the steel grade is sometimes based on the material stress response under quasi-static loading conditions derived from tensile tests performed in conventional universal testing machines (see for example [5]). Because the main goal of material selection for structural parts of power transformers is to improve mechanical performance, reduce weight and minimize costs while meeting the safety requirements during short-circuit faults, it follows that knowledge of the stress-strain mechanical behavior under medium to high rates of loading is crucial for choosing the steel grade and for designing shell form power transformers at the extreme conditions that are commonly found during short circuit faults.…”