The paper analyzes the problem of protection of a small active resistor for grounding the distribution network. The mentioned small active resistor is installed in the constellation of the associated winding of the power transformer in the feeder substation (one resistor per transformer or one resistor per substation). The application of the following protections was analyzed: (i) protection against bridging of a small active resistor, (ii) protection of an active resistor and back-up protection against short circuits with the ground in the distribution network and (iii) protection against high-resistance faults. An overview of the selection of basic technical data of current transformers for the connection of the mentioned protections (especially those that are installed in the constellation of windings of the energy transformer) is given.