Recently the communication network for power systems becomes a major focus in the development and deployment of smart grids. Particularly, how to validate whether or not a real-time network can fulfill the strict requirements on communications by the distributed power applications? The basic approach is by precise simulations of the underneath communication network! However, there are no modules available in the common tools for such simulations, including OPENT and NS-2. In this paper, we focus on the modeling and simulation of real-time Ethernet protocols that are used for fast protection in smart grids. As an example, we model and simulate the EtherCAT, a real-time Ethernet protocol. First, we analyze the packet level performance of the real-time Ethernet, including the delay model, the timing granularity of the packet delay, and the communication requirements. Second, we propose a simulation method for the modeling and operation of the protocol. The important synchronization and scalability issues are also investigated with our simulation method. Third, we implement the modules for the protocol in the OPNET simulator. Our extensive simulation results have demonstrated that the proposed modeling and simulation method are accurate and effective in modeling the packet-level performance of the real-time Ethernets. We also show that the simulation method for real-time Ethernet can be used to investigate the performance of the protocols under different configurations.