[en] This report documents the technical evaluation of the proposed design modifications and technical specification changes on grid voltage degradation for the Prairie Island Nuclear Generating Plant. The review criteria are based on IEEE Std-279-1971, IEEE Std-308-1974, and General Design Criterion 17 of the Code of Federal Regulations, Title 10, part 50, Appendix A requirements for determining the acceptability of the proposed system to protect the safety-related equipment from degradation of grid voltages