This paper makes researches on the digital output of electronic current transformers based on IEC60044-8 standard. The structure of electronic transformers

the physical layer

link layer and application layer of digital output are analyzed in detail. The implementation scheme is presented as well. MU function is achieved in stipulations by adopting DSP as main processor and external circuit

which can implement the real time and reliability

and the system design can be expended easily if needed. Finally

the impact on substation applying electronic transformers and future application are discussed.