Thermo Electrical Analysis and its Correlation in a DC Biased Power Transformer Subjected to Over and Under Excitations

The dc biased power transformer will be subjected to nonlinear operation, deteriorating its performance. This paper investigates the impact of dc bias on power transformer variables, focusing on losses and thermal distribution in laminated core and copper windings of the power transformer. The findings of these studies provide a guide for accurately determining the insulation requirements that can effectively sustain the consequences of dc bias. This paper presents a three-dimensional modelling technique and analyses the power transformer using constructional details and material properties. The finite element method is used to analyze three-phase 500KVA dry type, natural air-cooled power transformer with Ansys Maxwell software. The three-dimensional temperature distribution in the transformer parts is obtained using Ansys mechanical software. Thermal analysis is performed for various levels of excitation with varying DC bias, and the effects of the same are investigated. The main contribution of this study is a simple and efficient approach for investigating the thermal impacts and finding the correlations in a dc biased power transformer. Accurate detection of temperature distribution during the design stage is very important as its insulation requirement is directly determined by thermal constraints, allowing life span and health of the transformer to be optimized.