The current transformers that are most commonly used on the market are manufactured with transformation ratios that have a nominal secondary current of five amperes and several characteristics depend on this current. The current transformer's function is basically to supply a group of equipment for measurement or protection without it being directly connected to the primary circuit. Through the theoretical study of current transformers and the calculations involved, a study will be carried out into the possible replacement of these current transformers with others that have a nominal secondary current of one ampere, in order to reduce the cost of buying a current transformer by simply reducing losses and using more modern measuring and protection equipment, without there being a decline in the quality of the current transformer's operation and that of the measuring and protection systems.