The widely used electrical real-time digital simulation（RTDS） system plays an important role in the stability analysis， security assessment， relay protection equipment test， etc. With the adoption of electronic transformers， neither D/A conversion nor power amplification is needed in the RTDS system. The data output by simulation software can be directly used through format conversion. The structure and implementation of a new RTDS system based on IEC 61850 standard are discussed. The test model connecting the RTDS system and digital secondary devices is described. The practicality of the proposed RTDS system is validated by a 110 kV line all-digital relay protection module.