High Voltage Power Transformer Protection Parameters Calculation and Differential Protection Testing using a Three Phase Test Kit

The paper sets out the main protection functions used in substations for protecting power transformers as well as the parameters calculation for some of them. The case study will refer to a $400 / 110 \mathrm{kV}$ substation equipped with mobile cells in external GIS technology, in order to supply the 110 kV voltage of an industrial platform with a maximum power demand estimated at 270 MVA. In addition to the technical and economical criteria, the degree of safety in the supply of electricity users was considered a criterion of great importance in the process of developing the presented solutions. The calculation was made for differential protection as well as for distance protection and in addition to the actual calculation, the logic for determining the thresholds is presented. As the transformer differential protection is the main protection function, it was tested using a three phase testing kit to ensure proper functionality.