Due to the shortcomings of commercial filters and non-linear components for overvoltage protection in the conditions of synergy of neutron and gamma radiation and functional aging, the behavior of the hybrid protection circuit under the same conditions was examined. In order for the experimental procedure to correspond as closely as possible to the real situation, the load of the hybrid circuit was not adjusted by impedance. The standard model of the hybrid protection circuit recommended in accordance with IEC 1.3 is simulated using the software package PSPICE. To that end, it is necessary to create a varistor with appropriate elements. The equivalent inductance parameters were found to be stable in relation to the experimental conditions. It was also established that due to the synergy of neutron and gamma radiation and functional aging, there is a change in the steepness of the varistor characteristic and the tangent of the loss angle in the capacitors. The overall effect of neutron and gamma radiation and functional aging was tested on the hybrid circuit and on individual components. The experiments were performed under well-controlled laboratory conditions, and the combined measurement uncertainty of the experimental procedure did not exceed 5%.