Application and Design of the Modern Substation Automation Platform by Chris Trayhorn, Publisher of mThink Blue Book, May 14, 2007 This paper describes the application of the modern automation platform in electrical transmission substations. The applications described within are not “bleeding edge” or merely theoretical. Working, proven examples of everything described in this paper can be found in at least one U.S. or Canadian substation, but few substations include all platform applications. The modern automation platform consolidates solutions previously implemented in multiple physical boxes from different suppliers. A single automation platform can perform the roles of security gateway, SCADA RTU, communication processor, port switch, protocol converter, sequence of events recorder, alarm annunciator and substation HMI. Economic, technological and cyber security forces have driven this functional consolidation. Figure 1 depicts the many components of a traditional transmission substation automation system, while Figure 2 illustrates the configuration of the modern automation platform. Having fewer boxes reduces hardware, purchasing, installation and maintenance costs, while having a single configuration tool reduces training and configuration costs. Thanks to technological advances, powerful yet inexpensive processors can now perform complex data processing and display tasks in the tough substation environment without a fan, hard drive or other moving parts. Modern software development tools and operating systems are also ideally suited for the embedded, real-time environment. Therefore, technology is no longer a barrier to entry for niche vendors. Finally, since substation security functions are easier to manage through a single gateway, the centralized topography enabled by the automation platform allows a simpler and more secure approach to cyber security. Each of the roles of the modern automation processor is described below: Security Gateway The specialized security functions required in transmission substations include: Firewalls; Data encryption and VPNs; Local and centralized authentication; and Event and alarm logging. Secure physical routers/switches from traditional IT suppliers and security software running on PCs have traditionally provided a solution. However, transmission substation engineers prefer not to purchase and maintain separate IT-oriented boxes, some of which may not meet all substation environmental specifications and may require specialized and extensive training. To resolve this situation, the automation platform has taken on these security functions as resident tasks, with functions optimized and simplified for substation automation applications. Traditional SCADA RTU Functions The traditional substation remote terminal unit (RTU) has performed its task reliably in transmission substations since the advent of computers, reporting realtime data to one or more Masters and executing control commands. The challenge has been to get the RTU to do more than it was designed to do. Increasingly, users need to obtain SCADA data from IEDs using IED protocols, some of which are proprietary and require specialized knowledge to emulate. Users also need to move data securely from the RTU to nontraditional users. The modern automation platform performs all of the traditional RTU tasks plus these new tasks in a single package. Communications Processing Communications processing includes the tasks of protocol conversion and media conversion. These have often been handled by specialized and separately powered hardware boxes. Examples include separate bit-to-byte converters, legacy protocol to DNP3.0 converters, RS232-to- RS485 and serial-to-fiber converters and Ethernet-to-serial converters. However, all of these options increase cost, complicate automation system design and reduce system reliability. Alternately, the modern automation platform performs these functions with a modular software and hardware architecture that permits any Master or Slave protocol to be configured on any combination of built-in bit synchronous, RS232, RS485, fiber optic or Ethernet ports. The resulting design is cleaner, more affordable and more reliable. The modern automation platform also enables data to be routed in nonconventional ways, such as Master-Master (using the automation platform as a mailbox) and Slave-Slave (reading data from one Slave and writing these data to a second Slave). Distributed I/O With Accurate Time Most traditional RTUs have required all substation inputs and outputs to be wired back to a centralized location, particularly if the inputs needed to be time-stamped to an accuracy of one millisecond. Today high-performance distributed I/O modules with IRIG-B timecode formats can be mounted on substation breakers and transformers, with a single fiber optic connection routed back to the substation RTU or automation platform. Some distributed I/O designs can also synchronize I/O module time with IRIG-B being transmitted over the serial connection to the module, or using NTP over Ethernet, to further reduce IRIG-B wiring costs. Accurate Time Management Accurate time-formatting (such as IRIGB) and accurate time-stamping of events have been part of transmission substan tion automation design for at least 15 to 20 years. But there has been little coordinated and integrated management of time stamps from multiple IEDs in multiple protocols and to multiple Masters. For example, time-stamped events in proprietary relay protocols need to be transmitted to the SCADA Master in the SCADA protocol, typically as DNP3.0 events with time. In addition, IEDs that communicate using protocols that do not support time need to have a time stamp placed on events as they are received. Multiple SCADA Masters and HMIs may each require the same events with time but possibly in a different protocol. The modern automation platform handles these time management functions as standard routines. Local Logic Processing and Control Local logic processing and control for schemes such as breaker-and-one-half, synchro-check, breaker failure, underfrequency load shed and black start have traditionally been implemented in protective relays and dedicated programmable controllers. While this is still the case, the trend is toward less logic implemented in programmable logic controllers and more in the automation platform. The math and logic packages available in the automation platform are based upon open and well-supported tools such as Visual Basic and IEC 61131. Many logic tasks that require data from different parts of the substation are handled easily by the automation platform, as it is the central repository for all substation data. Protective Relay Record Management Traditionally it has been common to apply a separate communication processor or port switch to provide access to engineering data residing in substation protective relays. The tools to access and process records have also traditionally resided on remote PCs. Today the automation platform serves as a pass-through port switch, supporting dial-in connections as well as local and remote Ethernet connections. The automation platform can also filter and preprocess relay fault records, so that only pertinent records are retrieved for analysis (for example, filter-based upon fault distance) or to simplify analysis (for example, pulling apart separate relay events from one large flat “file” and integrating with record viewer packages). Substation HMI Substation engineers have always desired local tabular or graphic visualization of real-time operating conditions in the more critical transmission substations. The challenge has been to justify the relatively high cost of buying the HMI software, configuring the displays and maintaining the PC-based hardware platform and operating system. Users report that the highest single cost in substation automation is the PC-based HMI. Some of the PC hardware issues have been addressed with the advent of rugged PC power supplies and solid-state hard drives, but other costs remain. The modern automation platform can serve up standard preconfigured Web pages to a hardened PC or a laptop, reducing software configuration costs. Some automation platforms can also support video output of Web pages, allowing the use of a hardened LCD panel instead of a PC and further reducing hardware and maintenance costs. Alarm Annunciation Separate hardwired or serially driven alarm annunciator panels have been commonly applied in substations to alert operators of abnormal conditions. These hardware displays can be replaced with software-driven displays that are generated and served out from the automation platform and viewable as a Web page on any PC or as video on an LCD monitor. Displays can be identical to the old hardware- based displays or can change based upon real-time operating conditions. Sequence of Event Recording Dedicated sequence of event (SOE) recorders have been applied to determine the precise sequence of operation of substation equipment before, during and after substation events, and to verify proper operation (to a typical resolution of one millisecond). The modern automation platform, combined with high-performance distributed I/O, can replace the dedicated recorder with preconfigured Web pages served out to local or remote PCs. Savings include reduced wiring costs and reduced training and configuration time (same configuration tools and database as RTU, alarm annunciation and other functions). The Future Economic, technological and security forces will continue to drive the development and application of the single, powerful automation platform in transmission substations. Designs will become easier to configure and commission, and will take on new software tasks to convert data into information, and information into better operating decisions. These efficiencies will benefit all utilities, as they are challenged to contain costs without sacrificing service. Filed under: White Papers Tagged under: Utilities About the Author Chris Trayhorn, Publisher of mThink Blue Book Chris Trayhorn is the Chairman of the Performance Marketing Industry Blue Ribbon Panel and the CEO of mThink.com, a leading online and content marketing agency. He has founded four successful marketing companies in London and San Francisco in the last 15 years, and is currently the founder and publisher of Revenue+Performance magazine, the magazine of the performance marketing industry since 2002.