Case Study: Efficiently Replace PLC Automation Systems by Integrating IEDS with Fiber-Optic and Ethernet Communications in the Substation

This paper describes the successful replacement of an existing legacy PLC (programmable logic controller)-based substation automation design with integrated mission-critical protection intelligent electronic devices (IEDs). The new design replaces existing radios and leased-line modems with a hybrid serial and Ethernet local area network (LAN) with wide area network (WAN) connections. The new system exploits the full capabilities of communications processor technology to integrate existing protective relays and meters with new I/O (input and output) processors while also adding Ethernet connectivity to an expansion bay added to an existing substation. The various methods of communication connections provide a unique implementation advantages and pose unique data access security challenges. To that end, the case study also includes a description of the security methods employed to prevent unwanted electronic access to the substation, network, and IEDs