Abstract-Substation plays an important role in power system communications for safe and reliable operation of entire power networks. Substation communication networks are connected with various substation intelligent electronic devices (IEDs), which is substation systems lifeblood and the system availability is decided by its real-time performance. International Electrotechnical Commission (IEC) has been developed the standards based on object-oriented technologies for substation automation. IEC 61850 protocol has been applied widely in substation communication applications. It presents new challenges to realtime performance simulation and testing of protective relays. In this paper, an optimized network engineering tool (OPNET) or Riverbed modeler simulation tool/ software has been used for the modeling of IED in substation level network. Based on the simulation results, different types of data stream have been discussed, such as, periodic data stream, random data stream and burst data steam. The typical studies using these models, to construct substation automation system (SAS) network on the OPNET modeler or Riverbed modeler was made to reveal the impact of each affecting parameter or factor to the real-time performance of substation communications system, which is also incorporated in this report.Index Terms-IEC 61850, OPNET or Riverbed Modeler, Power system simulation, Real-time, Substation automation system (SAS), Transmission delay. I. INTRODUCTIONubstation intelligent electronic devices (IEDs) are transmitted data through the data communications network. Once the data packets transfer has been delayed and has not been reached to the target devices within the predetermined period of time, which may lead to extremely serious consequences, and endanger the substation and even the entire grid [1][2][3][4][5][6][7][8]. The key objectives for designing any substation automation architecture are interoperability between the IEDs, satisfaction of communication performance, and extensibility of the architecture. The IEC 61850 is a global communication standard for substation automation system (SAS) defines the communication between the IEDs and not only solves the interoperation problem but also specifies other system requirements like message performance, information security in the SAS networks [6]. Substation communication network transmission packets have strict delay requirements, real-time study for the underlying communication network, in particular, the media access control (MAC) layer protocol, while ignoring the real-time upper-layer protocols [2]. The transmission protocol, network load and networking mode are the main factors affecting the real-time performance of the SAS network [3][4]. Among the transmission delay constitution factors, message packaging and parsing take up most of the time, which relates to the transmission model and protocol [5].According to IEC 61850-5 standards, the messages transmission time requirements for the SAS network must be ensured under any operating conditions and cont...

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