Chuck Adamson, Southern California Edison
Bill Ackerman, ABB Power T & D Company
David Joy, AccessWare Inc.
One of the most significant advances in the area of electric utility automation is that of moving "real-time" SCADA and substation information onto the enterprise network. Traditionally a utility has been concerned with issues such as:
These issues are changing and new issues are emerging:
The primary objective is to make substation data more available to system operations and to all potential users within the utility.
Today, several methods exist to allow the realization of this objective and various utilities have been active in testing and implementing these over the past several years. Unfortunately, many approaches have been internally developed and "patched" together without adherence to any recognized standards. This leads in turn, to proprietary systems which "stand alone" and become, from the date of installation, an impediment to overall information integration. The need for an open systems approach will become even more compelling in the wake of deregulation and the requirement to provide interchange of data between utility companies.
Southern California Edison Grid Operation & Maintenance Division has just recently started up their first Substation Automation System (SAS). The beta (test) site was installed at the Eric Substation in Cerritos California, and a simulator unit (for operations personnel) was set up at the Test School in Alhambra. The state-of-the-art SAS system replaces the existing electro-mechanical relays and switches in the substations and SCE's plans are to install the new SAS equipment in approximately 400 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 extensive information related to maintenance and operations. This should permit a significant improvement in the reliability and efficiency of substation operations. Additionally, the new SAS panels are more space-efficient than the older panels, with a single SAS panel measuring 19" x 80" replacing five or more of the old-style panels which measure 3' x 7'each.
The SAS is being provided by ABB Power T & D Company, Power Automation and Protection Division. The SAS incorporates ABB's new DPU (multi-function relay / intelligent protective unit) technology with a new and powerful HMI (Human-Machine Interface). The HMI 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 other intelligent devices existing in the substation.
The DPU and TPU are powerful, intelligent electronic devices which provide access to substation operating parameters such as: current, voltage, real and reactive power, min/max metered values, demand metering values, protective settings, system configuration, waveform capture, and load profile capture. Multiple devices may be interconnected on a single communications network. A SPARC UNIX Workstation containing the PRICOM Plus software communicates to the various devices. Figure 1 illustrates a typical interconnection scheme.
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). DNP 3.0 has been recommended by the IEEE as the preferred protocol for communicating with IEDs, and is rapidly becoming an industry standard. Additionally, 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 data is available via the HMI located within each substation and is capable of providing approximately 4,500 pieces of information. To facilitate the management of large amounts of data, "objects" are created which represent various groups of like information. These objects are stored in the SAS memory and can be displayed on demand. The ABB PRICOM Plus operator package is based on technology developed by AccessWare, Inc. The AccessWare "Access Machine" technology, incorporated in the company's "AccessPoint" product family, 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. Utilizing standards such as OLE, DDE, SQL, OPC, HTML, HTTP, etc., 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 Human-Machine Interface (which is graphically and logically object-oriented). At the same time, the SAS provides remote access to its database via the Harris DNP 3.0 protocol. 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, or to additional SCADA Master Stations.
Access Machines can incorporate HMI/SCADA with added capability for MES (Management Execution Systems). 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, 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 users to configure, view, and print real-time data from the Access Machine without the need for special training or engineering assistance. The reduced load on engineering resources results in considerable savings of time and money for the utility.
Even more advanced and powerful is the link to the Internet technology within the Access Machine. Everyday users of the Internet, with their knowledge of how to operate products such as Internet Explorer and Netscape, can configure, link to, display, and print real-time data from the Access Machine. While it is unlikely that the utility will provide full operational 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 information will allow the utility industry to effectively manage its internal information network, or Intranet. (Intranet refers to a corporate network which utilizes the technologies and infrastructures of the Internet).
The Access Machine will become the key entry point to the utility's database of process data, providing the link between the SCADA systems and its MES strategies. For many of these strategies to be workable, 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 which is in constant operation (not just for emergency use). This type of strategy requires tight integration with the real-time SCADA database. Attempts to use information available from a relational database management system, or even a data historian, are likely to fall short of expectations.
The ABB 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 on the HMI screens as required, and linkage to the RTDB (and associated DPU information) occurs almost automatically.
An HMI screen, built by the flexible Graphical Display Builder, may consist of various layers. Any number of layers may be masked from view when the screen is presented to the operator; thus, the configuration engineers can create self-documenting screen formats by placing screen and object documentation into one or more screen layers. The layers containing the documentation are masked when the screen format is in normal use, but may be easily unmasked when needed. ABB PRICOM Plus makes extensive use of this feature.
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 it acts as a gateway to respond to requests for information coming from SCE's Switching Center Harris SCADA Host. Because the Access Machine is connected to the substation's local network, it has access to all of the data from all of the IED's in the substation. All of this data is available for acquisition by the Central Host computer via a single communications line, and using the same communications protocol. This represents a significant cost and maintenance advantage over having to have several communications lines or using an electro-mechanical switch to multiplex the devices over a single line. The Access Machine not only performs the multiplexing function, it also performs a protocol translation service.
At SCE, considerable costs reduction can be realized by using the Access Machine technology. The advantages include the following:
These are advantages that can be realized by any utility which makes use of this new and emerging technology.