This paper analyzes the application of 3-in-1 network,which includes MMS network of station level,GOOSE network and SV network of process level in smart substation.Being aimed at the problems of real-time performance and reliability of network communication,this paper proposes an implementation scheme of 3-in-1 network for smart substation based on IEC 62439-3(PRP/HSR)protocol and discusses it in detail.In this paper,research and development of the key equipments are introduced and relevant experiment verification and test results are summarized.Finally,this paper discusses the application design and analysis of distributed bus differential protection based on HSR.