The data traffic of smart substation process level sampled value（SV）network is analyzed.Centralized protection and monitoring devices based on SV networking and generic object-oriented substation event（GOOSE）networking are designed.The hardware and software design schemes of centralized protection and monitoring devices are described in detail.The design of the software realizes not only the general protection and control functions，but also the functions of the fast bus protection，reserve power source automatic connection and small current grounding line selection.Two application scenarios of centralized protection and monitoring devices used in smart substation are dealt with.Application in engineering practice shows that the design is feasible.