Simulation and analysis of 25 kA current injection transformer (CIT) with finite element method

Since current injection transformers (CIT) arc within the major group of the standard type test equipments in electrical industry, their performances arc very important. With the help of finite element method (FEM), some of the prominent problems can be solved. This paper reports the simulation and analysis of the current and flux distribution and thermal characteristics: hot-spot temperatures, warm and cooling periods, in a 25 kA (125 kVA) CIT. Accurate calculation of the value of the secondary winding hot-spot temperature at the design stage is becoming very critical in order to ensure that heat generation of the CIT is in the safe range; therefore the secondary winding losses, flux and current distribution were simulated by Ansys5.4 software package. Also the effects of induced eddy current due to dispersion reactance in the secondary windings was calculated with Cosmos/m software package and compare two results together. Finally the copper and core losses were computed, from which warm and cooling periods of secondary winding hot-spot temperature were extracted. The hot spot temperature rise was 98° C.