Memory soft errors induced by the single-particle effect have a non-negligible effect on microcomputer relay protection. This paper introduces the sources of Alpha particles and high-energy neutrons, as well as atmospheric neutron fluxes in some cities in China. The details of the neutron irradiation tests on relay protection devices and the method of obtaining the single particle failure rate in the field environment based on experimental data are discussed. Based on the existing reliability metrics, the acceptable failure rate of the single-particle effect of the relay protection device is promoted. Comparing this indicator with the failure rate obtained by the irradiation test, it can be judged whether the device fulfills the requirements of field operation. This method has a certain reference significance for evaluating the failure efficiency of single particles of relay protection devices. This work is supported by the Key Scientific and Technological Project of China Southern Power Grid Corporation (No. ZDKJXM20200056).