IMPROVING MAN-MACHINE INTERACTION IN CONTROL CENTERS: THE IMPORTANCE OF A FULL-GRAPHICS INTERFACE A. Almeida.do Vale M. J. Dias Gongalves Zita A. Vale Member,IEEE University of Porto/Faculty of Engineering Department of Electrical and Computer Engineering Rua dos Bragas - 4099 Porto Codex - Portugal Phone: 351-2-317107 Fax: 351-2-318787 Telex: 27323 FEUP P Email: zav@garfield.fe.up.pt KEYWORDS: SCADA/EMS Hardware Implementation and Design, User Interface, Full-Graphics Displays ABSTRACT - Control Centers are responsible for the control, supervision and monitoring of Power Systems. It is of primary importance that the software existing in Control Centers provides operators with the most important, recent and correct information about the state of the system. The use of semi-graphic consoles proved to be insufficient for this kind of tasks. In this paper we present a multi window system with zooming facilities in a full-graphics environment. This system helps operators providing them with the information they need in a more concise and friendly way. Some examples concerning the Portuguese Electrical Network are presented. Future improvements discussed. in this application are!.introduction Nowadays, Electric Power Systems are remotly controlled from Control Centers. These centers usually control a Power System extending through a large geographic area and including some tens of substations. In order to provide an efficient and real-time control, Control Centers must have access to a large volume of information about the state of the Power System. This information is acquired in measuring points installed all over the electrical network and transmitted to Control Centers using telecommunication systems. The whole system is usually known as a SCADA (Supervisory Control and Data Acquisition System) [ 1). The increasing complexity of Power Systems and the aim of delivering high quality electrical energy at minimum costs make Control Center operator tasks highly demanding. 'Control Centers include complex computerized applications but human operators still play the most important role in identifying problems and taking decisions. Recent experience has shown that, specially in emergency situations, the interpretation of the displayed information is a difficult task even for experienced and well-trained operators. In fact, man-machine interfaces used in today's Control Centers provide operators with great amounts of information, without taking into account human limitations. The main factors that contribute to the incompatibility between the system and operators are: the great amount of information displayed at the same time without any filtering, the incapacity of the graphics displays of showing at the same time information of generic and specific level, and the non-existence of a general representation of the entire Electrical Network in the library of graphic images. The solution for this kind of problems includes the use of a multi-window system with zooming facilities in a full-graphics environment in SCADA implementation and design. This must be supported by good knowledge about Control Center operators needs and with optimum control of the displayed information. This will help operators in receiving the most important information about the Electrical Network in order to take the most appropriate actions. This paper presents a software package that is being developed at the University of Porto, using c language in a "Decsystem 5500 RISC - Digital" with graphic support of a color high 273
resolution X terminal "Tektronics". This software is designed to Portuguese Control Centers. alter the existing ones or to treat a different network. The new Portuguese Control System has been installed between May 1988 and February 1989. The system is hierarchic and includes the National Control Center (NCC) at the top level, two Subestation Operation Centers (SOC) at Vermoim and Sacavem and four Hydroplant Control Centers (HCC). The National Control Center uses two machines VAX 8600 with 3 semi-graphic consoles with a total of 7 video displays. The use of this kind of display does not allow a friendly manmachine interface. In our system the operator can easily get information, of generic and specific level, in the same display, due to the possibility of opening different windows for displaying information. The most important information is displayed in the screen with top priority, on the other hand the less important information can be accessed only by operators demand. It provides an image of the whole Portuguese electrical network. This image includes information about topology and alarms that is continuously updated according to data that is acquired in the Power System and transmitted to Control Centers. The main goal of this screen is to provide dispatchers with general information about the whole network. On the other hand, it identifies the areas of the network that are causing the generation of alarms. Under request, operators can easily access more detailed information about a specific area (zoom view) of the network and a specific plant, without loosing a general view of the entire network. Our software prov.ides, as the conventional user interfaces, the electrical diagram of each plant. Besides this, it includes a set of new possibilities such as small windows displaying information about typical load diagrams, or about each equipment (electric and mechanic characteristics, faults,.. ). This system includes a drawing tool, built in the same environment, that allows operators to build, expand or alter graphic images without any programming effort. This facility may be used when is necessary to include new plants, 2. USER INTERFACE - AN OPEN SUBJECT The great evolution in computer hardware, made it possible to process great volumes of information in very short periods of time. However human abilities have not increased that much and some computer applications do not respect human limitations [2]. This gap between computer and human abilities is today widely recognized and research works concerning human and computer interaction are becoming more and more important [3]. In our opinion, the design of the User Interface (UI) of computer applications, should not be treated in the restricted limits of displays design. In fact, the design of the UI involves mainly two different questions: a) what information is to be displayed b) how will that information be displayed Both questions have equal importance and neglecting one of them makes effort involved in the other. useless the Answering question a) involves a deep understanding of the problems being treated. Artificial Intelligence techniques are presently used for this purpose [4]. Question b) concerns directly the building of the displays to be presented to operators and is still an open question. Considering that the way in what information is presented determines how useful it will be, the UI must be regarded as a crucial aspect of any computer application. The UI is obviously even more important in the case of real-time applications as the ones installed in Control Centers. In case of an accident, decisions must be based on different kinds of information and be taken as quickly as possible. In these situations, a good UI is of great help to operators. The use of full-graphics displays presents a wide range of new possibilities to the UI of Energy Management Systems (EMS) and SCADA. As these application are very complex and expensive, electrical utilities must carefully decide on the use of full-graphics technology in their EMS [5,6]. 274
Full-graphics technology allows to introduce a set of new facilities: multi-window systems, scroll windows, zooming and panning, extensive use of menus and buttons actuated through the use of the mouse. This is specially important because of the flexibility that can be reached using this facilities. Using this technology, operators can access different levels of information at the same time in a very friendly and flexible way. The use of full-graphics displays in the UI of an EMS must however consider some particular aspects of this application. It is important to use the new possibilities only when they constitute a real improvement to the UI. Some of them, that seem very attractive at the first sight, proved not to be well accepted by operators. In particular, operators do not seem to like to work with a lot of windows with resizing and dragging possibilities [5]. Moreover, window manipulation increases the time response in case of emergency situations. The optimal solution is a multi-window system where window manipulation is controlled by the application itself and by operators. This has also the advantage of providing. an easier management of the displayed information ("obliging" operators to see the most important information). In general, full-graphics create a new philosophy technology may of displaying information: - a great volume and variety of additional information is ready to be displayed, on operator's demand - zooming and panning provide easy and flexible access to the available information - analog values are used to construct graphics (lines, bars, pie charts) showing, at a glance, the most important information - icons (to be clicked on) are used to have direct and quick access to more detailed information about the objects they represent. Colors [6,7] are still a very important means of providing and reinforcing information. Its use is of special importance in the following situations : indication of device status - differentiation of voltage levels (e.g. in transmission lines) - indication of severity of alarms - helping in the interpretation of graphics. Till now we have only addressed the use of full-graphics displays for an overall renovation of Control Centers [6,8]. However, this technology has a much more immediate application in the existing Control Centers, in the case of new appended applications [4]. In fact, a new application (e.g. a Knowledge Based System) can be appended to the existing EMS, running in a different machine communicating with the main computer through a Local Area Network (LAN). In these cases, the machine used for the new application is usually a workstation providing a fullgraphics UI. 3. SYSTEM OVERVIEW The application that is being presented in this paper, has been developed using C Language in a Decsystem 5500 RISC-DIGITAL, with a graphic support of a color high resolution X terminal. It was implemented with the aid of the XWindows programming libraries, and permits the simulation and the building of a electrical network representation for future control and supervising. The Main Display of the application includes three subwindows with the following contents: - Mapboard window containing a graphic representation of the entire electrical network (Synoptic Board) - Menu window containing a wide variety of menus, specially used for the building of the different zoom views, electrical diagrams of the plants and the mapboard - Zoom window were the zoom views are displayed. The program has two entirely different ways of operation. The first one is used for building the different plant diagrams. The second is the user interface application, intended to use in real-time operation. 3.1. Display Building When the program starts, a menu window is displayed in the bottom right corner of the main window, that allows operator to build new diagrams and expand the existing ones. There are three types of diagrams that can be 275
modified or created: - the mapboard the zoom windows - the plant diagram windows. For this kind of operation, the user only has to press the mouse button in the desired menu button. 3.1.1. Mapboard building The different building options within this application are : - inclusion of the different plants in the mapboard. - inclusion of the different lines connecting the plants in the synoptic board. The menu concerning the inclusion of the plants is shown in figure 1. ~ - Substation 1~1- Thermal power plant Green - Green line (220 kv) Blue - Blue line (150 kv) Black - Black line (60 kv) Figure 2 - Building lines The procedure for including new lines is very simple being only necessary to choose the density, color, and location by pressing the mouse button in the desired places. The program detects automatically the name of a plant when an extremity of the line is selected. While the user is including new lines, a text file named "LINHAS.MJG" is being updated. 3.1.2 Zoom building : The program gives to the operator the possibility to build the different zoom zones existing in the screen. For this kind of action it must be selected from the initial menu the option "Zoom". Then it will be presented a second menu named "Building Zoom". The format of the specified menu is as shown below in figure 3. 1~1- Hydro power plant ] --------.1- "Building Lines" menu ~- "Building Plant Diagrams" menu Figure 1 - Building window As the operator is including in the board the new plants, a text file named "PORTINST.MJG" is being updated. If the operator wants to include new lines in the synoptic board it is necessary to select the option "Lines" and a new menu is displayed (see figure 2). 0 - Substation in small size 00 [ll] ~ - Substation in large size - Hydro power plant - Thermal power plant - Plant - Includes the name of the station I~ - Menu for including the different lines interconnecting all the plants Figure 3 - Building zoom Q - Line of small density B- Line of medium density ~ - Line of large density Red - Red line (400 kv) The procedure for building the zoom images is very simple and it is only necessary to select with the mouse the plants to install and its location in the zoom window. There are essentially three steps to build the image: - choose the type of plant to include - choose the desired place to display the 276
in the zoom window - select "Plant" to include the name of the plant. The program displays upon the zoom window a grid to help the selection of the desired place in the image to build. A image reporting this stage of building a zoom window is show below in figure 4. ~ to indicate that the line to include starts and ends in a plant existing in the zoom view [J) to include terminals located in vertical way Q to include terminals located in a horizontal way Define Area is used to select the upper left corner and the right bottom. While the zoom and the lines are being inserted in the screen, two files are being updated ( "ZOOM.MJG" and "ZOOMLI.MJG"). Figure 4 - Building a zoom window When the image is completed in terms of the plants existing in that zoom area, the user can easily include the different lines that interconnect the plants. When the referred option is selected, a new menu, called "Building Zoom lines " is displayed, having the aspect shown in figure 5. Figure 5 - Building zoom lines This menu includes the following buttons: - Four zones corresponding to four different color lines (different voltage levels) - Start button to initiate the building of a new line in the zoom window - End button to terminate the building of a new line l!5ji to indicate that the line to include starts in a plant existing in the zoom view and ends in a plant not existing in the zoom view 3.1.3 Plant diagram building : The other kind of images that the program displays is the electric diagram of the plants. The operator can easily build this diagrams needing only to choose in the first menu the option corresponding to this item. Then a new window is opened showing the plant diagram to alter or a white window to bui 1 t another plant diagram. The menu provided to the user to build this kind of diagrams has the following items: - generator - transformer (Two-winding) - auto-transformer (Up and Down position) - circuit breaker - disconnecter - busbar - line - bypass disconnecter - interbar - small characters to include panels numbers and line names - large characters to include device numbers, voltage levels and titles for the stations - possibility to clear a already included symbol - save option to include the name of the built plant. An example of a plant diagram built with this application can be found in figure 6. 277
or equivalent device, if it is installed (track ball). Figure 6-3.2. Normal operation :1, [ I Plant diagram The other way of using this application is to use the different images built as it was described before, to control, supervise and interact with an electrical network. In normal operation the main display of the application has the aspect displayed in figure 7. The only device that operators must use to easily and rapidly access to the different images of the controlled network is the mouse In the mapboard (the principal area where the actions are taken) there are hot spots that correspond to the plants and zoom areas. Dispatchers experience shows that the names of the different plants are easily memorized after a short period of intense use and interface with the controlled network. Due to this aspect the mapboard in this application does not show the name of each plant, but only the corresponding symbol included in its geographic location. The operator can access this information only by pressing the left button of the mouse over the desired plant symbol. The name is immediately displayed in a small window displayed in the right bottom corner of the mapboard window. To get more detailed information, the user must press the center button of the mouse to display a zoom image of the selected area. The aspect of a zooming operation is shown in figure 7. It can be observed that the selected zoom area is marked in the synoptic board with a rectangle. In this zoom window the operator can have a different level of information without loosing the image of the entire V /CCL3 srn/s\ic2 Figure 7 - Main display window 278
network, what was not possible in the non full-graphic displays. This application also provides operators with the display of plant diagrams. To display this type of information it is only necessary to press the right button of the mouse above the desired station in the mapboard. Immediately a graphic window is displayed showing a complete description of the plant diagram. An example showing this type of images is presented in figure 6 (Vermoim substation). 4. CONCLUSIONS The User Interface is presently accepted to be a very important factor for the success of a computer application. Together with Knowledge Based Systems, a full-graphics based interface can help Control Center operators in performing their tasks in an efficient and more friendly way. In this paper, we presented a software package, based on XWindows, that provides a very friendly and flexible User Interface for Control Centers. This package includes applications for building, with minimum effort, the displays to be used in real operation. The principal characteristic of the application presented is the great simplicity of the files that include the different graphic images (text files) and the great facility of integration in a more extended software package of EMS/SCADA hardware design. 3) 4) 5) 6) 7) 8) c. Weisang and K. Zinser, "Graphics and Knowledge-Based Operator Support", The Second International Forum on Expert Systems and Computer Simulation in Energy Engineering, Erlangen, Germany, pp; 5.4.1-5.4.5, March 17-20, 1992 z. A. Vale and A. M. Moura, "An Expert System with Temporal Reasoning for Alarm Processing in Power System Control Centers", 92 SM 602-3, IEEE Power Engineering Society 1992 Summer Meeting, Seattle, U.S.A, July 12-16, 1992 S. Clark, J. Steventon and R. Masiello, "Full-Graphics Man-Machine Interface for Power System Control Centers", IEEE Computer Applications in Power, Vol. 1, No. 3, pp. 27-32, July 1988 J. Young, T. Green and T. Desmond, "Building Quality Full-Graphics Displays", IEEE Computer Applications in Power, Vol. 5, No. 2, pp. 17-22, April 1992 K. Imhof and c. Arias, "Show it with Colors. Connectivity, Status, and Value Information in Energy Management Systems", IEEE Computer Applications in Power, Vol. 3, No. 4, pp. 11-15, October 1990 E. Euxibie, P. Jourdin, P. Audousset and F. Audrain, "A New Alarm Processing for the Forthcoming National Control System of Electricite De France", The third IEE International Conference on Power System Monitoring and Control, London, United Kingdom, 1991 5. REFERENCES 1) W. Ackerman and w. Block, "Understanding Supervisory Systems", IEEE Computer Applications in Power, Vol. 5, No. 4, pp. 37-40, October 1992 2) Zita A. Vale and A. Machado e Moura, "An Expert System to Assist Operators of the Power System Control Centres", Information-Decision-Action Systems in Complex Organisations, Oxford, United Kingdom, IEE Conference Publication No. 353, pp. 110-114, 6-8 April, 1992 This work is partially sponsored by JNICT (The National Institute for Scientific Research). 279