Electric Utility Benefits from Access Machine Technology
By Bill Ackerman, ABB Power T & D Co., Chuck Adamson, Southern California Edison, and David Joy, AccessWare Inc.
One of the newest trends in the area of electric utility automation is moving “real-time” SCADA data onto the enterprise network. Various reasons exist for this trend which represents a paradigm shift. Traditionally, the utility has been concerned with issues such as investment-oriented, regulated business environment; proprietary computer systems, protocols and interfaces; independent systems, with “islands of information;” and functionality limited in scope and features. These issues are changing and new issues are emerging, now leading to the paradigm shift: competitive business environment, brought on by government deregulation; “open systems” architectures utilizing domestic and worldwide industry standards; integrated systems, allowing easier access to data residing in all areas of distribution; and extended data-access functionality with expanded scope and features.
The primary objective is to make substation data more available to centralized operations and other levels within the utility. Various options exist today to allow the realization of this objective. Utilities have been active in testing these various options over the past few years. Unfortunately, many of these options have been “home-grown” and patched together without the realization of standards. This leads to proprietary systems which do not fit in with the current paradigm shift. This lack of an “open systems” approach will become even more apparent in the wake of deregulation and the need to provide interchange of data between utility companies. Southern California Edison (SCE) Grid Operation & Maintenance Division recently brought up its first substation automation system (SAS).
The beta test site was installed at Eric Substation in Cerritos, Calif., and a simulator unit (for operations personnel) was set up at the test school in Alhambra. The state-of-the-art SAS replaces the existing system of mechanical relays and switches in the substations. SCE`s current plans are to install the new SAS equipment in approximately 300 substations between now and the year 2000. The new system can be remotely operated from the switching center and is self-calibrating. The SAS can capture and provide information related to maintenance and operations and represents a significant improvement in the reliability and efficiency of substation operations. Additionally, the new SAS panels are more space efficient than the older panels. A single SAS panel measuring 19 inches by 6 feet 8 inches can replace two of the old-style panels which are 36 inches by 7 feet each. The SAS is being provided turnkey by ABB Power T & D Co., Distribution Systems Division (Sanford, Fla.). The SAS incorporates ABB`s new DPU (multi-function relay intelligent protective unit) technology with a new and powerful user interface. The user interface is a part of the ABB PRICOM (Protection Information Communication) Plus operator package which provides the connectivity to the protective equipment as well as to the other intelligent devices existing in the substation.
The DPU is a powerful intelligent electronic device which provides access to the low- and medium-voltage substation operating parameters such as current, voltage, power, minimum/maximum metered values, demand metering values, protective settings, system configuration, waveform capture and load profile capture. Multiple DPUs may be connected together on the same communications network. A SPARC UNIX workstation containing the PRICOM Plus software communicates to the various DPUs. The SAS is connected to the SCADA master at the switching center and serves as a data-concentration device between the IEDs at the substation and the existing Harris master. The master communicates with the SAS using the Harris DNP 3.0 communications protocol, which is a subset of the IEC 870-5 specification for communications protocols (widely used in Europe and becoming more popular in the United States). Information is capable of traveling in a bi-directional mode such that the substation can be remotely operated from the switching center.
The substation protective unit information is available via the user interface at the substation. Each protective unit is capable of providing approximately 4,500 pieces of information. To make the large amount of data manageable, “objects” are created to represent various groups of like information. The objects are stored in the SAS memory and can be displayed at will. The PRICOM Plus operator package is based on technology developed by AccessWare Inc., Houston, Texas. The AccessWare “access machine” technology offers a standard and unified solution to substation automation and integration.
The access machine consists of an “object-based” architecture providing a real-time database, a message database, a historical database, a relational object configuration manager, and an I/O subsystem for interfacing with SCADA and process control devices. The access machine provides on-demand graphical displays of presentation, summary and processed information. The real power of the access machine is the access it provides to the data it contains. Utilizing standards such as OLE, DDE, SQL, OPC, HTML and HTTP, information links can be provided to real-time and historical data in a manner which is compatible with the data users. For example, at SCE the SAS provides local access to its database via the PRICOM Plus user interface (which is graphically and logically object-oriented). At the same time, the SAS provides remote access to its database via the Harris DNP protocol. Alternatively, or simultaneously, the very same data could be provided to a relational database (such as Informix) via a standard SQL interface and to a spreadsheet or desktop database via DDE links. Because PRICOM Plus is built on top of access machine technology, it presents SCE operators with a composite local view of the substation`s operations, while at the same time acting as a gateway to respond to requests for information coming from SCE`s switching center Harris SCADA host. The PRICOM Plus implementation of the access machine strategy consists of a high degree of device modeling using the object-oriented features available in both the real-time database (RTDB) and the graphical display builder. Each protective relay is depicted as a complex object in the database. Depending on its configuration, a DPU may be represented by one of various complex objects already pre-configured in PRICOM Plus. Where more than one DPU is used in a substation, there may be several instances (occurrences) of the complex object in the RTDB. Visual objects are taken from the graphical object library and placed o
Access machines include the experience of SCADA with added capability for management execution systems (MES). With the use of a network of access machines, a “data warehouse” can be constructed to provide maximum functionality and reliability without having to collect everything into one monster computer. The task of administration is therefore distributed and supported at each access machine location. The key idea is to distribute the management of the data but centralize the access to the data. The ability to view real-time data in a Microsoft Excel or Lotus 1-2-3 spreadsheet, for example, means that it is no longer necessary to budget engineering time to produce report formats and support a large user base. It is now possible for a back office secretary to configure, view and print real-time data from the access machine without the need for special training or engineering assistance. Even more revolutionary and powerful is the link to the brand new Internet technology which the access machine provides. Now, everyday users of the Internet, with their knowledge of how to use products such as Internet Explorer and Netscape, can configure, link to, display and print real-time data from the access machine. While it will probably never be true that the utility will provide information on the Internet, the use of the very same technology that has allowed the effective management of and access to a large network of a tremendously large distributed database of information will allow the utility industry to effectively manage its information network, or Intranet. (Intranet refers to a corporate network which utilizes the technologies and infrastructures of the Internet).
The access machine should become the key access point to the utility`s database of process data, providing the link between the SCADA systems and its MES strategies. For many of the MES strategies to be viable, access to real-time or near real-time data is an absolute requirement. For example, for a utility to become more competitive it may wish to implement a comprehensive active load management strategy. Because the active load management is in constant operation (as opposed to emergency use), it must have access to the real-time SCADA database. Attempts to use information available from a relational database management system, or even a data historian, are likely to fail.
William J. Ackerman received his bachelor`s of science degree in electrical engineering from Iowa State University and his master`s of science degree in electrical engineering degree from the University of Wisconsin. Ackerman is currently with the ABB Power Automation & Protection Division as manager of substation automation systems. He is a senior member of the IEEE and the Power Engineering Society.
Chuck Adamson started in the utility automation field as a protection and control technician for Southern California Edison (SCE) in 1986. Adamson is currently a protection and control specialist for SCE with project management responsibilities for the substation automation system installation.
David Joy is director of application engineering at AccessWare. He has participated in the design and implementation of numerous utility SCADA projects over the span of 15 years.
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New space-efficient substation automation system panels replace older panels at the Eric Substation.