In my work, I explained the energy system in general and the way how the electricity flows from the power plants until it reaches the households, I tried to introduce transformer as an electrical machine, explain its operation, and I showed the transformers different types, I measured the short circuit current and operating currents for selecting circuit breakers, disconnectors and air coil. The power was given to 12.5 MVA, the voltage levels of the main transformer were 132 kV and 11 kV and according to this I selected the transformers for the grid