In this paper, an analysis of the operation of the differential protection of auxiliary consumption transformers of the power plant unit in the event of a fault outside the protection zone was performed, taking into account the influence of the occurrence of of current transformers saturation. In the case of short circuits in the system resulting in high-intensity currents and saturation characteristics of current transformers, distortion of the current waveform on the secondary occurs, affecting the current waveform on the secondary and the operation of the protection system. Analyzes were performed on the software model of the protective device and on the actual device, by injecting currents into the protective device using a test case. The responses of the software model of the protective device and the actual device were compared. Network modeling and analysis were performed in the DlgSILENT PowerFactory software package, and the DOBLE test case was used to test the operation of the protective device.