Substations are a crucial element at the transmission and distribution level of electric power systems. The primary substation equipment (power transformers and high voltage switching equipment) is used to transfer and transform electric energy by stepping up or down the voltage in transmission substations. Secondary equipment (such as IEDs, Intelligent Electronic Devices) is used to control, protect and monitor primary equipment and the rest of the substation while relying on a variety of communication protocols.The IEC 61850 standard is a viable candidate for current Substation Automation Systems (SAS) as well as for future Smart Grid (SG) substations. SG is the next generation power grid, which aims to improve reliability and efficiency, reduce the cost of electric energy, and minimize environmental impacts. SG will be relying on effective and reliable communication, and the IEC 61850 standard shows the potential for providing such a communications framework. Currently, the delay performance evaluation of this standard has been carried out at the distribution level. At the transmission level, where data rates are high and there is a low latency requirement, this standard has yet to show its performance.In future Smart Grids, transmission substations will be part of a self-healing network that identifies the faults blackouts and automatically connects disconnects the feeders and re-routes power to ensure security of the grid. According to IEC 61850, the communication requirements for transmission substations will be more time-critical. In this work, the IEC 61850's delay performance is evaluated at a transmission substation between different bays in the case of one outgoing feeder’s failure. OPNET software is used as a simulation tool. In OPNET, devices such as Analog Merging Units (MUs) and IEDs were implemented according to the IEC 61850 standard. Delay performance for Generic Object Oriented Substation Events (GOOSE) messages is evaluated in terms of End-to-End (ETE) GOOSE message delay, with without Virtual Local Area Network (VLAN) attributes according to IEEE 802.1Q and with or without Quality of Service (QoS) attributes according to IEEE 802.1p.