上海交通大学：《电力系统自动化》课程教学资源（推荐论文）Internet-based SCADA display system

Internet-Based SCADA Display System Bin Qiu,Hoay Beng Gooi, Yilu Liu,Eng Kiat Chan In the deregulated environment, information is the key to secure operation,profitability,customer retention,market advantage,and growth for the power industry EYEWIRE he operational and commercial needs of the power demand access,platform independence,and transaction industry require information systems to not only management for the design of the online SCADA display perform traditional functions but also support many system of the new functions,specifically to meet the needs of competition with deregulation.The rapid development Web-SCADA Background of the Internet and distributed computing have opened IT plays an increasingly important role in all fronts.In the the door for feasible and cost-effective solutions. deregulated environment,information becomes the key This article describes and demonstrates a unique to secure operation,profitability,customer retention. Internet-based application in a substation automation market advantage,and growth for the power industry. system that is implemented based on the existing system SCADA systems are essential parts of the distribution control and data aquisition (SCADA)system and very- management system(DMS)and energy management sys- large-scale integration (VLSD)information technologies tem (EMS)that employ a wide range of computer and (IT).The user can view the real-time data superimposed communication technologies.However,traditional on one-line diagrams generated automatically using VLSI SCADA communication is established mainly for intra- placement and routing techniques.In addition,the user company information exchange,especially for protec- can also control the operation of the substation at the tion and control.Low bandwidth and communication server site.The choice of Java technologies,such as Java isolation hinders information exchange and interopera- Native Interface (JND,Java Remote Method Invocation tion.Information sharing among different utilities or (RMD,and Enterprise Java Bean (EJB),offers unique and even individual divisions of the same utility is difficult, powerful features,such as zero client installation,on- complex,costly,and sometimes impossible.Deregula- tion results in mergers and consolidation,pushing for B.Qiu and Y.Liu are with Virginia Polytechnic Institute and State Uni- more extensive intra-and inter-utility information versity,Blacksburg.Virginia.H.B.Gooi is with Nanyang Technological exchange,integration,consolidation,dissemination,and University,Singapore.E.K.Chan is with Power Automation Pte,Ltd. open access.Intercompany communication and integra- Singapore. tion of data from various control centers,power plants, 14 IEEE Computer Applications in Power ISSN0895-0156/02/s17.002002IEEE

14 IEEE Computer Applications in Power ISSN 0895-0156/02/$17.00©2002 IEEE T he operational and commercial needs of the power industry require information systems to not only perform traditional functions but also support many of the new functions, specifically to meet the needs of competition with deregulation. The rapid development of the Internet and distributed computing have opened the door for feasible and cost-effective solutions. This article describes and demonstrates a unique Internet-based application in a substation automation system that is implemented based on the existing system control and data aquisition (SCADA) system and very￾large-scale integration (VLSI) information technologies (IT). The user can view the real-time data superimposed on one-line diagrams generated automatically using VLSI placement and routing techniques. In addition, the user can also control the operation of the substation at the server site. The choice of Java technologies, such as Java Native Interface (JNI), Java Remote Method Invocation (RMI), and Enterprise Java Bean (EJB), offers unique and powerful features, such as zero client installation, on￾demand access, platform independence, and transaction management for the design of the online SCADA display system. Web-SCADA Background IT plays an increasingly important role in all fronts. In the deregulated environment, information becomes the key to secure operation, profitability, customer retention, market advantage, and growth for the power industry. SCADA systems are essential parts of the distribution management system (DMS) and energy management sys￾tem (EMS) that employ a wide range of computer and communication technologies. However, traditional SCADA communication is established mainly for intra￾company information exchange, especially for protec￾tion and control. Low bandwidth and communication isolation hinders information exchange and interopera￾tion. Information sharing among different utilities or even individual divisions of the same utility is difficult, complex, costly, and sometimes impossible. Deregula￾tion results in mergers and consolidation, pushing for more extensive intra- and inter-utility information exchange, integration, consolidation, dissemination, and open access. Intercompany communication and integra￾tion of data from various control centers, power plants, B. Qiu and Y. Liu are with Virginia Polytechnic Institute and State Uni￾versity, Blacksburg, Virginia. H.B. Gooi is with Nanyang Technological University, Singapore. E.K. Chan is with Power Automation Pte, Ltd, Singapore. Bin Qiu, Hoay Beng Gooi, Yilu Liu, Eng Kiat Chan © EYEWIRE In the deregulated environment, information is the key to secure operation, profitability, customer retention, market advantage, and growth for the power industry

and substations has become a necessity.Existing infor- line routing.Hightower algorithm is chosen as the rout- mation management systems cannot satisfy the new ing algorithm.Instead of storing the entire grid in its challenges,as more and faster information has now memory,it only stores line information.Therefore,it become desired by many players.Technological executes faster and has a lower memory requirement advances in networking have made it possible to devel- than that of alternative algorithms,such as Lee and op a low-cost Internet display system for accessing infor- Maze. mation over the Internet. Web-based conception has been elaborated and Dynamic Data Linkage implemented by researchers all over the world.Their After routing,the SCADA system data will be dynamically experience has indicated that the Internet/intranet can linked to the static one-line diagram.The real and reac- be successfully employed in real-time systems.But how tive power(MW/Mvar),voltage,current,and running sta- to integrate the existing SCADA system with the Internet tus of the power system components will be linked to is a challenge. the database and displayed at the position close to the respective component.When the display is refreshed One-Line Diagram Autogeneration each time,their values will be retrieved automatically As the power system becomes more and more complex, from the database and updated on the one-line diagram. the one-line diagram layout is becoming increasingly complex and,in turn,is placing even higher demands on SpecNET System Design one-line diagram autogeneration tools.Automated layout Given the pressure to bring new services to market,an consists of two primary functions: important challenge facing the software is how to inte- Determining the positions of the modules (substa- grate new services and network elements to the existing tion or its components),called placement system.This article describes an example of the integra- Interconnecting the modules with wiring,called tion of the existing SCADA software with the advanced routing. network technologies.The system is based on the VLSI placement and routing algorithms have been Siemens Spectrum SCADA software,which is a distrib- used for the substation one-line diagram autogeneration uted network automation system designed to run on the As shown in Figure 1,the autogeneration of the one-line Unix system.It is used as the major monitoring and con- diagram contains stream input data,placement,routing, trol system supporting raw substation connection infor- and dynamic data linkage. mation and real-time data.Spectrum was developed under C/C++/Pascal.Integrating Spectrum software with Stream Input Data the advanced network technologies means the redesign The stream input data contains the connectivity informa- of the whole system which is difficult and inefficient. tion of the network.The data items include the compo- Facing this problem,a software prototype named nent's names,start and end nodes,component ratings, SpecNET was developed based on the advanced comput- and modeling parameters. er and network technologies.SpecNET is workflow soft- Placement and Routing Dynamic When the data is read by the autogenera- Stream Input Data Placement Routing Data tion module,a substation topology is cre- Linkage ated according to the connectivity of the components.The topology is accessed by Figure 1.Process involved in one-line diagram generation the placement and routing modules. Component placement determines the location of the component within the one- 0320110C line diagram.It determines the minimum JavaCon SpecNET Server length of interconnection and minimizes Client SCADA line crossovers.It distributes the nodes of components evenly in the frame.Place- ment is crucial in the overall design cycle, JavaCon as its output must be routable.The over- Client SCADA all quality of the layout is determined in this stage 出 Milestone methods of the VSLI design JavaCon Database Database such as the force-directed method is used Server Client for the power component placement. SCADA After placement,the diagram is ready for Figure 2.Main configuration of SpecNET January 2002 15

January 2002 15 and substations has become a necessity. Existing infor￾mation management systems cannot satisfy the new challenges, as more and faster information has now become desired by many players. Technological advances in networking have made it possible to devel￾op a low-cost Internet display system for accessing infor￾mation over the Internet. Web-based conception has been elaborated and implemented by researchers all over the world. Their experience has indicated that the Internet/intranet can be successfully employed in real-time systems. But how to integrate the existing SCADA system with the Internet is a challenge. One-Line Diagram Autogeneration As the power system becomes more and more complex, the one-line diagram layout is becoming increasingly complex and, in turn, is placing even higher demands on one-line diagram autogeneration tools. Automated layout consists of two primary functions: ■ Determining the positions of the modules (substa￾tion or its components), called placement ■ Interconnecting the modules with wiring, called routing. VLSI placement and routing algorithms have been used for the substation one-line diagram autogeneration. As shown in Figure 1, the autogeneration of the one-line diagram contains stream input data, placement, routing, and dynamic data linkage. Stream Input Data The stream input data contains the connectivity informa￾tion of the network. The data items include the compo￾nent’s names, start and end nodes, component ratings, and modeling parameters. Placement and Routing When the data is read by the autogenera￾tion module, a substation topology is cre￾ated according to the connectivity of the components. The topology is accessed by the placement and routing modules. Component placement determines the location of the component within the one￾line diagram. It determines the minimum length of interconnection and minimizes line crossovers. It distributes the nodes of components evenly in the frame. Place￾ment is crucial in the overall design cycle, as its output must be routable. The over￾all quality of the layout is determined in this stage. Milestone methods of the VSLI design such as the force-directed method is used for the power component placement. After placement, the diagram is ready for line routing. Hightower algorithm is chosen as the rout￾ing algorithm. Instead of storing the entire grid in its memory, it only stores line information. Therefore, it executes faster and has a lower memory requirement than that of alternative algorithms, such as Lee and Maze. Dynamic Data Linkage After routing, the SCADA system data will be dynamically linked to the static one-line diagram. The real and reac￾tive power (MW/Mvar), voltage, current, and running sta￾tus of the power system components will be linked to the database and displayed at the position close to the respective component. When the display is refreshed each time, their values will be retrieved automatically from the database and updated on the one-line diagram. SpecNET System Design Given the pressure to bring new services to market, an important challenge facing the software is how to inte￾grate new services and network elements to the existing system. This article describes an example of the integra￾tion of the existing SCADA software with the advanced network technologies. The system is based on the Siemens Spectrum SCADA software, which is a distrib￾uted network automation system designed to run on the Unix system. It is used as the major monitoring and con￾trol system supporting raw substation connection infor￾mation and real-time data. Spectrum was developed under C/C++/Pascal. Integrating Spectrum software with the advanced network technologies means the redesign of the whole system which is difficult and inefficient. Facing this problem, a software prototype named SpecNET was developed based on the advanced comput￾er and network technologies. SpecNET is workflow soft￾Figure 2. Main configuration of SpecNET Figure 1. Process involved in one-line diagram generation Stream Input Data Placement Routing Dynamic Data Linkage

acts as a bridge between the existing FNET Server SCADA system and SpecNET server through a JNI connection.The JNI pro- vides Java code that runs within a Java Virtual Machine (VM)to operate with Client Database JavaCON PMI applications and libraries written in other Operation languages,such as C,C++,and assembly. JNI is used when the SpecNET server Figure 3.SpecNET server function wants to talk with the SCADA Server.Fig- ure 4 shows how the JNI ties the SpecNET server site application to the SCADA serv- SpecNET er. SCADA SpecNET Server C Code Java Code JavaCON consists of the SpecNET C Code C/C++code site and SpecNET Java code Functions Exceptions site.The SpecNET C/C++code site con- Functions tains a function module and library mod- Libraries JNI Classes ule.The function module is coded using Functions SCADA server application program inter- Functions VM face (APD,therefore,it can talk with the SCADA server kernel program like a native component to get the raw data, Figure 4.JavaCON JNI structure and talk with the database to retrieve real-time information.Libraries are used ware that models,coordinates,and integrates some of to define the corresponding methods.The SpecNET Java the SCADA functions,such as the one-line diagram gen- site contains VM,classes,and exception modules.VM eration and real-time data display.Figure 2 illustrates can locate and invoke native methods on the SpecNET C the SpecNET architecture.Internet/intranet users code site and act as a bridge to directly communicate access the SCADA system data through the SpecNET with Spectrum.Classes define the actual methods.The server.JavaCON,which stands for Java connectivity to exception module is used to handle the exception case SCADA,is used as a data communication bridge during the communication. between the existing SCADA system and the SpecNET server.The SpecNET server receives messages from the Client/Server Communication existing SCADA system through JavaCON and provides The evolution of distributed computer architecture the necessary support for client site person-machine results in the birth of client/server architecture. interface (PMD.Useful information will be saved to the Client/server structure provides the scalability and database through the connection between SpecNET robustness required to support mission-critical applica- server and database server. tions throughout the enterprise comprising thousands of users.In the SpecNET system,communication SpecNET Server between the SpecNET Server,SCADA server,and cus- As the global Internet continues to grow,Java is uniquely tomers is based on the client/server architecture.Two suited to build the next generation of network applica- methods are used for the communication:RMI and sock- tions.The SpecNET server is written entirely in Java, et communication. based on the client/server architecture to fit the different The RMI system allows an object running in one VM platform requirements.The functions of SpecNET are to to invoke methods on an object running in another Java manage resources needed to support SCADA system VM.RMI provides the mechanism by which the server online services.As shown in Figure 3,the server sup- and the client communicate and pass information back ports four roles: and forth.SpecNET RMI implementation comprises two ■JavaCON function separate programs: ■Client function ■RMI server ■PMI function ■RMI client. ■Database operation. RMI server creates remote services objects,makes references to them accessible,and waits for clients to JavaCON Interface to SCADA Server invoke methods on these remote objects.RMI client gets Currently,existing SCADA systems are developed based a remote reference to one or more remote objects in the on different platforms using different languages.For server and then invokes methods on them.Figure 5 illus- example,Spectrum was coded in C/C++,and JavaCON trates SpecNET RMI distributed application that uses the 16 IEEE Computer Applications in Power

ware that models, coordinates, and integrates some of the SCADA functions, such as the one-line diagram gen￾eration and real-time data display. Figure 2 illustrates the SpecNET architecture. Internet/intranet users access the SCADA system data through the SpecNET server. JavaCON, which stands for Java connectivity to SCADA, is used as a data communication bridge between the existing SCADA system and the SpecNET server. The SpecNET server receives messages from the existing SCADA system through JavaCON and provides the necessary support for client site person-machine interface (PMI). Useful information will be saved to the database through the connection between SpecNET server and database server. SpecNET Server As the global Internet continues to grow, Java is uniquely suited to build the next generation of network applica￾tions. The SpecNET server is written entirely in Java, based on the client/server architecture to fit the different platform requirements. The functions of SpecNET are to manage resources needed to support SCADA system online services. As shown in Figure 3, the server sup￾ports four roles: ■ JavaCON function ■ Client function ■ PMI function ■ Database operation. JavaCON Interface to SCADA Server Currently, existing SCADA systems are developed based on different platforms using different languages. For example, Spectrum was coded in C/C++, and JavaCON acts as a bridge between the existing SCADA system and SpecNET server through a JNI connection. The JNI pro￾vides Java code that runs within a Java Virtual Machine (VM) to operate with applications and libraries written in other languages, such as C, C++, and assembly. JNI is used when the SpecNET server wants to talk with the SCADA Server. Fig￾ure 4 shows how the JNI ties the SpecNET server site application to the SCADA serv￾er. JavaCON consists of the SpecNET C/C++ code site and SpecNET Java code site. The SpecNET C/C++ code site con￾tains a function module and library mod￾ule. The function module is coded using SCADA server application program inter￾face (API), therefore, it can talk with the SCADA server kernel program like a native component to get the raw data, and talk with the database to retrieve real-time information. Libraries are used to define the corresponding methods. The SpecNET Java site contains VM, classes, and exception modules. VM can locate and invoke native methods on the SpecNET C code site and act as a bridge to directly communicate with Spectrum. Classes define the actual methods. The exception module is used to handle the exception case during the communication. Client/Server Communication The evolution of distributed computer architecture results in the birth of client/server architecture. Client/server structure provides the scalability and robustness required to support mission-critical applica￾tions throughout the enterprise comprising thousands of users. In the SpecNET system, communication between the SpecNET Server, SCADA server, and cus￾tomers is based on the client/server architecture. Two methods are used for the communication: RMI and sock￾et communication. The RMI system allows an object running in one VM to invoke methods on an object running in another Java VM. RMI provides the mechanism by which the server and the client communicate and pass information back and forth. SpecNET RMI implementation comprises two separate programs: ■ RMI server ■ RMI client. RMI server creates remote services objects, makes references to them accessible, and waits for clients to invoke methods on these remote objects. RMI client gets a remote reference to one or more remote objects in the server and then invokes methods on them. Figure 5 illus￾trates SpecNET RMI distributed application that uses the 16 IEEE Computer Applications in Power Figure 4. JavaCON JNI structure SCADA Server C Code SpecNET C Code SpecNET Java Code Functions Functions Functions Exceptions Classes VM JNI Functions Libraries Figure 3. SpecNET server function FNET Server Client Database Operation JavaCON PMI

registry to obtain a reference to a remote object. SpecNET RMI server calls the registry to associate (or Registry bind)a name with a remote object.The client looks Client up the remote object by its name in the server's reg- RMI RMI istry and then invokes a method on it.SpecNET RMI Authentication server objects include user authentication,database Client Socket SpecNET RMI Server operation,one-line diagram autogeneration,etc.The Autogeneration SpecNET server takes requests from clients,runs RMI them,and returns any results. RMI Client When a remote client connects to the SpecNET Real-Time Data server for public information,clients can access the information immediately.For confidential informa- tion,the SpecNET server redirects the client Database requests to the user authentication object,asking for Figure 5.Java RMI architecture user name and password,then,according to the user level,allocating user to the different objects. When the user wants to see the substation autogenera- connections of all the components according to some tion one-line diagram,the SpecNET server runs the JNI connectivity priorities.The component symbols are then communicating with the SCADA server.It will then added to the topology.Dynamic information,such as obtain the one-line diagram raw connection information voltages and MW/Mvar flows,are automatically linked to from the SCADA server,generate the one line diagram, each component to display the updated SCADA informa- and then send the final layout to the client for display. tion through the PMI.The final layout is stored in the After that,a socket connection will be set up between database.Full graphical editor functions are supported the SpecNET server and client site,and the real-time by the GUl at the SpecNET server.Within a substation, analog data,breaker status information,and trans- components can be manipulated and edited via the former taps will be transmitted from the SCADA system mouse and keyboard.Users can choose component sym- to the client site.Multithreading is used to process mul- bols from the library or design their own.Component tiple client requests.A separate thread will be set up to properties may be edited by double-clicking the mouse process the data transmission when a client activates a on the respective component which in turn calls up a dia- connection to the SpecNET server. log box.Panning and zooming are also supported when viewing the details of a network or a substation.The Person-Machine Interface applicable manipulations are select,drag,and double- PMI provides a means for utility engineers,planners,and click.Multiple objects may be selected,and the object's upper management to access the SCADA system data.The functionality of the PMI,for most of SpecNET-On-Line SCADA System ■回☒ the time,is only limited to viewing the overall File Network Running Record Another Menu picture of the system being monitored.People eu2口aprP@m四PC P.T.LS ST C OL FV AL.K>yO accessing the PMI do not take an active part in Site Map One-Line Diagram Configuration ControlProtection Communication Database controlling the system.The PMI at the client site has the same graphical user interface (GUD)as HUKIT PANIA that of the server site.This design enables the user to view the details of the substation conve- niently.When the user accesses the SpecNET server,a security mechanism is triggered to allow only the authorized user to view the SCADA information. The PMI is supported by the autogeneration of one-line diagrams and GUl displays.As shown in Figure 1,the autogeneration of one-line dia- grams contains stream input data,placement, routing,dynamic data linkage,and graphic edi- tor.The stream input data supplies substation component information for creating the substa- tion topology.The vertices of the topology with- out the components will be placed using the VLSI's placement algorithm.Routing will route Figure 6.Map of Buona Vista January 2002 17

January 2002 17 registry to obtain a reference to a remote object. SpecNET RMI server calls the registry to associate (or bind) a name with a remote object. The client looks up the remote object by its name in the server’s reg￾istry and then invokes a method on it. SpecNET RMI server objects include user authentication, database operation, one-line diagram autogeneration, etc. The SpecNET server takes requests from clients, runs them, and returns any results. When a remote client connects to the SpecNET server for public information, clients can access the information immediately. For confidential informa￾tion, the SpecNET server redirects the client requests to the user authentication object, asking for user name and password, then, according to the user level, allocating user to the different objects. When the user wants to see the substation autogenera￾tion one-line diagram, the SpecNET server runs the JNI communicating with the SCADA server. It will then obtain the one-line diagram raw connection information from the SCADA server, generate the one line diagram, and then send the final layout to the client for display. After that, a socket connection will be set up between the SpecNET server and client site, and the real-time analog data, breaker status information, and trans￾former taps will be transmitted from the SCADA system to the client site. Multithreading is used to process mul￾tiple client requests. A separate thread will be set up to process the data transmission when a client activates a connection to the SpecNET server. Person-Machine Interface PMI provides a means for utility engineers, planners, and upper management to access the SCADA system data. The functionality of the PMI, for most of the time, is only limited to viewing the overall picture of the system being monitored. People accessing the PMI do not take an active part in controlling the system. The PMI at the client site has the same graphical user interface (GUI) as that of the server site. This design enables the user to view the details of the substation conve￾niently. When the user accesses the SpecNET server, a security mechanism is triggered to allow only the authorized user to view the SCADA information. The PMI is supported by the autogeneration of one-line diagrams and GUI displays. As shown in Figure 1, the autogeneration of one-line dia￾grams contains stream input data, placement, routing, dynamic data linkage, and graphic edi￾tor. The stream input data supplies substation component information for creating the substa￾tion topology. The vertices of the topology with￾out the components will be placed using the VLSI’s placement algorithm. Routing will route connections of all the components according to some connectivity priorities. The component symbols are then added to the topology. Dynamic information, such as voltages and MW/Mvar flows, are automatically linked to each component to display the updated SCADA informa￾tion through the PMI. The final layout is stored in the database. Full graphical editor functions are supported by the GUI at the SpecNET server. Within a substation, components can be manipulated and edited via the mouse and keyboard. Users can choose component sym￾bols from the library or design their own. Component properties may be edited by double-clicking the mouse on the respective component which in turn calls up a dia￾log box. Panning and zooming are also supported when viewing the details of a network or a substation. The applicable manipulations are select, drag, and double￾click. Multiple objects may be selected, and the object’s Figure 5. Java RMI architecture Client Client Client Registry Authentication Autogeneration Real-Time Data Database SpecNET RMI Server RMI RMI RMI RMI Socket Figure 6. Map of Buona Vista

DB口属四回下☑+A壁西3Os? modules that read and write data to the database tables. Database operation on the server site is through RMI and JDBC.JDBC is a Java API for executing SQL state- aver f雪bistatio ments.It lets the Java program send SQL statements to the appropriate database.Four steps are executed Bus.1 A Bus 2A before using the JDBC API to access the database: 2 Import the JDBC classes Register the JDBC driver Open a connectivity to the database NeF2B出buH6n Ayer0 Substation Query the database. But 3 A Bus 4A After these steps,the Java program can talk to the data- base. System Security Some of the most potentially valuable developments in the high-speed technology resolution are Internet, Figure 7.Overall map of substation Intranet,and Extranet that connect electric utility com- panies via applications directly to external organizations, SpecNET-On-Line SCADA System 回 such as their customers,IPPs,distributors,brokers,and Network Another Menu @a口口ane面回on阿国LNHO strategic partners.Information exchange and manipula- tion have different performance and security require- SHe NapOne-Line DiagramCordiguration ControlProtection Communication Database ments.Together they will determine the type of 91-G003 networks used for communication and how to set G)PF-0.78 authority.Three access-levels are used for the SCADA 383Mw TR-0123 system: 0.00H2 45 MVA Intranet level Bus A 33.00 KV ■Extranet level Bus B0.00 KV ■Internet level.. Rem Loc Loc Rem Loc Loc Security is typically less of a concern for the intranet level,because intranet applications are deployed within the firewall.Performance of the intranet is limited only by the speed of the enterprise network.Currently,the C1 C1 scalability of Ethernet is well defined at 10/100 Mbps, .00Mw0.00 0.00 000 with the 1/10 Gbps Ethernet on its way.High perfor- .00Mvar0.00 0.00 0.00 0.00 MVar 0.00 MVar mance Ethernet technologies can fully meet the intranet TR0140 TR-0141A TR-0141日 TR-1 142 TR-1141A TR-1141B performance requirements. Extranet applications extend the intranet architecture Figure 8.Detailed map of substation beyond the firewall by allowing the information access over a public network.Data security at this level could attributes may be altered via a pop-up dialog box. be protected by using firewall,cryptography,digital cer- At the server site or within the Intranet,control may tificate (DC),and public key infrastructure (PKD.The be issued to open or close breakers through the one-line performance of the extranet is more of a concern,since display.After the SCADA receives the command,the dis- internetwork delays must be considered.However, play reflects the updated status of the breaker. extranet is almost always connected via high-speed leased lines and is,therefore,less susceptible to the Database Operation bandwidth limitations. The SpecNET database stores the static and dynamic data At the Internet level,the requirements for information of the SCADA system.Most of the databases can be used exchange should be less critical in terms of performance for storing historical data with the Java database connec- and security.Transaction security can sometimes be tivity and open database connectivity (JDBC/ODBC)dri- ensured by using secure hypertext transfer protocol ver.It provides a convenient data-accessing mechanism (HTTPS)for Web information exchange,technology already on an NT server.The historical data consists of logged supported by many Web browsers.Data security technolo- data,events,and dynamic data of one-line diagrams.The gies of extranet can also be used at the internet level. system status and the real-time data are stored in the database at a periodicity specified by the user.Access to Implementation the database is provided through a series of interface The actual implementation consists of three major mod- 18 IEEE Computer Applications in Power

18 IEEE Computer Applications in Power attributes may be altered via a pop-up dialog box. At the server site or within the Intranet, control may be issued to open or close breakers through the one-line display. After the SCADA receives the command, the dis￾play reflects the updated status of the breaker. Database Operation The SpecNET database stores the static and dynamic data of the SCADA system. Most of the databases can be used for storing historical data with the Java database connec￾tivity and open database connectivity (JDBC/ODBC) dri￾ver. It provides a convenient data-accessing mechanism on an NT server. The historical data consists of logged data, events, and dynamic data of one-line diagrams. The system status and the real-time data are stored in the database at a periodicity specified by the user. Access to the database is provided through a series of interface modules that read and write data to the database tables. Database operation on the server site is through RMI and JDBC. JDBC is a Java API for executing SQL state￾ments. It lets the Java program send SQL statements to the appropriate database. Four steps are executed before using the JDBC API to access the database: ■ Import the JDBC classes ■ Register the JDBC driver ■ Open a connectivity to the database ■ Query the database. After these steps, the Java program can talk to the data￾base. System Security Some of the most potentially valuable developments in the high-speed technology resolution are Internet, Intranet, and Extranet that connect electric utility com￾panies via applications directly to external organizations, such as their customers, IPPs, distributors, brokers, and strategic partners. Information exchange and manipula￾tion have different performance and security require￾ments. Together they will determine the type of networks used for communication and how to set authority. Three access-levels are used for the SCADA system: ■ Intranet level ■ Extranet level ■ Internet level. Security is typically less of a concern for the intranet level, because intranet applications are deployed within the firewall. Performance of the intranet is limited only by the speed of the enterprise network. Currently, the scalability of Ethernet is well defined at 10/100 Mbps, with the 1/10 Gbps Ethernet on its way. High perfor￾mance Ethernet technologies can fully meet the intranet performance requirements. Extranet applications extend the intranet architecture beyond the firewall by allowing the information access over a public network. Data security at this level could be protected by using firewall, cryptography, digital cer￾tificate (DC), and public key infrastructure (PKI). The performance of the extranet is more of a concern, since internetwork delays must be considered. However, extranet is almost always connected via high-speed leased lines and is, therefore, less susceptible to the bandwidth limitations. At the Internet level, the requirements for information exchange should be less critical in terms of performance and security. Transaction security can sometimes be ensured by using secure hypertext transfer protocol (HTTPS) for Web information exchange, technology already supported by many Web browsers. Data security technolo￾gies of extranet can also be used at the internet level. Implementation The actual implementation consists of three major mod￾Figure 7. Overall map of substation Figure 8. Detailed map of substation

The user can view the real-time data superimposed on one-line diagrams generated automatically using VLSI placement and routing techniques ules,as shown in Figure 2.The first module is the Siemens Spectrum SCADA server running on a Unix workstation with the Solaris operating system.The sec- Home Interface ond module is the SpecNET server running on a PC with Client Authen Bean Windows NT server and Internet information server (IIS) Remote Interface to support Web publishing and gateway function.The EJB Container company FireWall is used to provide data security for Client EJB Server the enterprise network in a distributed environment.The client side is a PC with Java-enabled Web browser,such Home Interface as Netscape or Explorer.Communication between the Real-Time Info Client SpecNET server and the Java client is through high- Remote Interface speed Ethernet.The system database resides in the EJB Container same SpecNET server.The PMI consists of multiple dis- plays,each giving a unique window into the overall sys- Figure 9.EJB-based SpecNET architecture tem condition.The highest level is the overall map that presents an overview distribution of the substations. interface (JNDD naming service.Then the client talks The second and third levels represent a smaller area of with beans through home and remote interfaces.The the entire map but with more details in the area dis- EJB framework offers two types of enterprise beans: played.The lowest level of the display is the substation's ■Session one-line diagram.Through the zooming and panning ■Entity. functions,the user can view the details of every substa- A session bean is a nonpersistent object that operates tion component. exclusively on behalf of the client session that creates it. Consider an example.Figures 6,7,and 8 display the The session bean is not shared among multiple clients. steps to view the one-line diagram of the hypothetical Client authentication is a typical example of the session substation.The substation is accessed by selecting the bean.An entity bean typically represents specific data or rectangular area to be enlarged at each level.The collections of data in persistent storage,such as shared dynamic data of the one-line diagram is being updated. information.Real-time information display can be Data such as voltages,MW/Mvar flows,and breaker sta- designed as an entity bean. tus of the simulated power system are automatically transferred from the server's database. For Further Reading B.Qiu and H.B.Gooi,"Internet-based SCADA display systems (WSDS) EJB-Based System Design for access via Internet,"IEEE Trans.Power Syst,pp.206-212,May 2000. J.Lee and J.H.Chou,"Hierarchical placement for power hybrid cir- SpecNET as a service provider provides services request- cuits under reliability and wireability constraints,"IEEE Trans.Reliabili- ed to the online SCADA server.With the rapid increase of y,vol.45,pp.200-207,Jun.1996. software programs in size and complexity,it is very impor- S.M.Sait and H.Youssef,VLSI Physical Design Automation:Theory tant to reduce high software cost and complexity while and Practice,McGraw-Hill,1995. increasing reliability and modifiability.With the advances M.J.Menz and B.Payne,"Servers in SCADA applications,"IEEE Trans.Industry Applic,pp.1295-9,Sep.,1997. of Internet technology,more distributed systems are built E.R.Harold,Java Network Programming,O'Reilly Assoc.,1997. to meet diverse application needs.EJB technology pro- vides low-level services such as support for transactions, Biographies concurrency,persistence,security,and life cycle manage- Bin Qiu is a Ph.D.candidate at Virginia Tech.He received M.S.degrees ment for each service.Therefore,EJB can be used in the in electrical engineering from Xi'an Jiaotong University,China,and SpecNET system design for better performance.Figure 6 Nanyang Technological University,Singapore,in 1997 and 1998,respec- tively.He worked in Power Automation Pte.,Ltd.(a joint venture illustrates the EJB-based SpecNET architecture. between Singapore Power and Siemens)from 1998-2000 as a network The EJB server is used to manage resources needed and software engineer.His interest includes power system automation to support the EJB container.An EJB container runs and computer/network applications in power systems.He may be within the EJB server and provides a scalable,secure, reached via e-mail,qiubin@vt.edu. Hoay Beng Gooi is an associate professor at Nanyang Technologi- and transactional environment in which enterprise cal University.His main research interests are power system operation, beans operate.Enterprise beans are server-side Java economics,and computation.His email address is ehbgooi@ntu.edu.sg. objects that talk with the SCADA server or database. Yilu Liu is a professor at Virginia Tech.Her main research interests A client obtains a reference to a bean by looking up are Internet and IT applications related to power system monitoring and control.She may be reached via e-mail,yilu@vt.edu. the bean's registered naming in the Java name directory Eng Kiat Chan is managing director of Power Automation Pte,Ltd., January 2002 19

January 2002 19 ules, as shown in Figure 2. The first module is the Siemens Spectrum SCADA server running on a Unix workstation with the Solaris operating system. The sec￾ond module is the SpecNET server running on a PC with Windows NT server and Internet information server (IIS) to support Web publishing and gateway function. The company FireWall is used to provide data security for the enterprise network in a distributed environment. The client side is a PC with Java-enabled Web browser, such as Netscape or Explorer. Communication between the SpecNET server and the Java client is through high￾speed Ethernet. The system database resides in the same SpecNET server. The PMI consists of multiple dis￾plays, each giving a unique window into the overall sys￾tem condition. The highest level is the overall map that presents an overview distribution of the substations. The second and third levels represent a smaller area of the entire map but with more details in the area dis￾played. The lowest level of the display is the substation’s one-line diagram. Through the zooming and panning functions, the user can view the details of every substa￾tion component. Consider an example. Figures 6, 7, and 8 display the steps to view the one-line diagram of the hypothetical substation. The substation is accessed by selecting the rectangular area to be enlarged at each level. The dynamic data of the one-line diagram is being updated. Data such as voltages, MW/Mvar flows, and breaker sta￾tus of the simulated power system are automatically transferred from the server’s database. EJB-Based System Design SpecNET as a service provider provides services request￾ed to the online SCADA server. With the rapid increase of software programs in size and complexity, it is very impor￾tant to reduce high software cost and complexity while increasing reliability and modifiability. With the advances of Internet technology, more distributed systems are built to meet diverse application needs. EJB technology pro￾vides low-level services such as support for transactions, concurrency, persistence, security, and life cycle manage￾ment for each service. Therefore, EJB can be used in the SpecNET system design for better performance. Figure 6 illustrates the EJB-based SpecNET architecture. The EJB server is used to manage resources needed to support the EJB container. An EJB container runs within the EJB server and provides a scalable, secure, and transactional environment in which enterprise beans operate. Enterprise beans are server-side Java objects that talk with the SCADA server or database. A client obtains a reference to a bean by looking up the bean’s registered naming in the Java name directory interface (JNDI) naming service. Then the client talks with beans through home and remote interfaces. The EJB framework offers two types of enterprise beans: ■ Session ■ Entity. A session bean is a nonpersistent object that operates exclusively on behalf of the client session that creates it. The session bean is not shared among multiple clients. Client authentication is a typical example of the session bean. An entity bean typically represents specific data or collections of data in persistent storage, such as shared information. Real-time information display can be designed as an entity bean. For Further Reading B. Qiu and H.B. Gooi, “Internet-based SCADA display systems (WSDS) for access via Internet,” IEEE Trans. Power Syst., pp. 206–212, May 2000. J. Lee and J.H. Chou, “Hierarchical placement for power hybrid cir￾cuits under reliability and wireability constraints,” IEEE Trans. Reliabili￾ty, vol. 45, pp. 200-207, Jun. 1996. S.M. Sait and H. Youssef, VLSI Physical Design Automation: Theory and Practice, McGraw-Hill, 1995. M.J. Menz and B. Payne, “Servers in SCADA applications,” IEEE Trans. Industry Applic., pp. 1295-9, Sep., 1997. E.R. Harold, Java Network Programming, O’Reilly & Assoc., 1997. Biographies Bin Qiu is a Ph.D. candidate at Virginia Tech. He received M.S. degrees in electrical engineering from Xi’an Jiaotong University, China, and Nanyang Technological University, Singapore, in 1997 and 1998, respec￾tively. He worked in Power Automation Pte., Ltd. (a joint venture between Singapore Power and Siemens) from 1998-2000 as a network and software engineer. His interest includes power system automation and computer/network applications in power systems. He may be reached via e-mail, qiubin@vt.edu. Hoay Beng Gooi is an associate professor at Nanyang Technologi￾cal University. His main research interests are power system operation, economics, and computation. His email address is ehbgooi@ntu.edu.sg. Yilu Liu is a professor at Virginia Tech. Her main research interests are Internet and IT applications related to power system monitoring and control. She may be reached via e-mail, yilu@vt.edu. Eng Kiat Chan is managing director of Power Automation Pte, Ltd., Figure 9. EJB-based SpecNET architecture Client Authen Bean EJB Server EJB Container EJB Container Real-Time Info Client Client Home Interface Remote Interface Home Interface Remote Interface The user can view the real-time data superimposed on one-line diagrams generated automatically using VLSI placement and routing techniques