Open Distributed EMS/SCADA System

Transcription

1 208 Open Distrbuted EMS/SCADA System Open Distributed EMS/SCADA System Norikazu Toshida Mario Uesugi Yuji Nakata Masaaki Nomoto Tomonobu Uchida ABSTRACT: Based on a recently emerging trend in the development of computer and communication technology, The Kansai Electric Power Co., Inc. and Hitachi, Ltd. have developed an open distributed energy management /supervisory control and data acquisition (EMS/SCADA). Its hardware, network, and operating comply with international or de facto standards and implement SCADA and state-ofthe-art power application software, providing load forecasting, power apparatus outage scheduling for maintenance, and power flow control, etc., with new methodologies and concepts. This paper introduces the concept of an open distributed database, software architecture, and power application software as a result of a joint study and migration work by The Kansai Electric Power Co., Inc. and Hitachi, Ltd. since the early 1990 s. Since workstations and other components, whose performance is expected to improve in future, can easily be added to the, we believe that the s lifecycle has been extended by the open distributed architecture, thus protecting customer investment. INTRODUCTION ENERGY management /supervisory control and data acquisition (EMS/SCADA) s have previously been constructed as centralized s using proprietary control computer and operating s. But a centralized imposes a burden on power utility company in the sense that it is sometimes difficult and uneconomical to expand or upgrade the. When a utility wants to improve and/or add some functions, it sometimes has to upgrade the existing computer s memory capacity or replace it with a higher-grade computer. On the other hand, a recently emerging trend in the development of computer and communication technology has been making it possible to establish open distributed computer s. Such technology is also being introduced into EMS/SCADA s. The requirements for such a new EMS/SCADA supported by latest technology are: (1) Expandability and flexibility (2) Conformity to international standards (3) High reliability (4) High functionality and high performance (5) High-level human interface The Kansai Electric Power Co., Inc. and Hitachi, Ltd. have developed a new EMS/SCADA that meets all these requirements. NEW EMS/SCADA SYSTEM FOR KANSAI ELECTRIC POWER COMPANY IN JAPAN The Kansai Electric Power Co., Inc. is responsible for the generation, transmission, and distribution of electricity in the Kansai region of Japan. The maximum demand to date in this region was 31,520 MW in The operation of the network is hierarchical; namely, there is one central load dispatching center (CLDC), one block load dispatching center, and eight local load dispatching centers. The CLDC is responsible for supply/demand control and supervisory control of high-voltage (500 and 275 kv) networks. The existing EMS/SCADA was built with a centralized architecture in the 1980s. The joint study by The Kansai Electric Power Co., Inc. and Hitachi, Ltd. for migrating from the existing to a new EMS/ SCADA started in the early 1990s. The migration was completed in the following two steps. (1) Step 1 (1995): The open distributed infrastructure, consisting of servers, workstations, and local area networks with SCADA functions, was built. Power application software to support load forecasting, coordination of power apparatus outage scheduling for maintenance, and power flow control was implemented. (2) Step 2 (1998): New equipment was added for supply/demand control, voltage/stability monitoring,

2 Hitachi Review Vol. 47 (1998), No enhancing unit commitment, and power restoration after network failure. The number of input points was increased in order to make it possible to run the voltage/ stability control. SYSTEM CONFIGURATION The configuration is shown in Fig. 1. It is a client/server configuration consisting of servers and engineering workstations (EWSs) which are mutually connected through local area networks (LANs) using FDDI (Fiber Distributed Data Interface) or Ethernet* 1). The servers are front end processors, SCADA servers, supply/demand control servers, and file servers. The engineering workstations provide the human interface. Open distributed The problems of traditional centralized s are (a) the functions, performance, and number of input/ control points designed at the initial design stage are fixed and it is normally difficult to change such parameters; (b) if the utility tries to prepare a considering future expansion to higher functions, higher performance, and more input/control points, it must prepare larger computers than required at the initial stage, which raises the initial investment; (c) it is generally difficult to connect the with other suppliers devices or s because the operating and interface are proprietary. In order to solve the above problems the new is scalable both vertically and horizontally, as shown in Table 1. This is achieved using the open and distributed concept as the basic philosophy. It is essential to use servers, EWSs, operating s, and networks that all comply with international or de facto standards and to build application software based on those platforms. The standards actually used for the new EMS/ SCADA are: Off-line LAN Weather Network information Calculation center Coordination Other EMS General-purpose application LAN Historical network data by popular database (ORACLE*) File server (HIDIC-RS90/800 Model 10) Human interface EWS For planning Power apparatus outage scheduling Fault supervision Power flow control Historical data recording Off-line LAN SCADA server (HIDIC-RS90/800 Model 30) Demand/supply control server Maintenance server (HIDIC-RS90 /800 Model 30) Network analysis server Maintenance LAN Front end processor (HIDIC-V90/55) Communication for network Data acquisition and conversion Detection of change of status On-line data Human interface EWS Display network status Display supply/demand status Display network fault Display trend graph of analog data For on-line *ORACLE is a trademark of Oracle Corporation, USA. Fig. 1 System Configuration. System configuration and function distribution are shown. Vertical and horizontal scalability can be achieved by this configuration.

3 210 Open Distrbuted EMS/SCADA System Table 1. Horizontal and Vertical Expandability Horizontal and vertical expandability are required for an EMS/ SCADA. Horizontal expandability Vertical expandability Servers and EWSs can be added to the without modifying application software. Servers and EWSs can be upgraded without modifying application software. (a) Operating : UNIX* 2 ) (b) Network (LAN): FDDI and Ethernet (c) Network Protocol: TCP/IP (transmission control protocol/internet protocol), UDP/IP (user datagram protocol/internet protocol) (d) Graphical interface: Motif* 3), X11* 4) Network Redundant Ethernets are used to connect servers and EWSs. Redundant FDDIs are used as the major on-line LAN to connect servers. FDDI is used rather than Ethernet for this in order to prepare for future increases in network transactions. TCP/IP and UDP/ IP are used for communication protocols among servers and EWSs. As UDP/IP is used to transfer the measured values from servers to EWSs, there is little effect on the CPU loading of other servers or on LAN loading even if the number of EWSs or display screens increases. As UDP/IP does not guarantee the receipt of data by all the EWSs, the server (sender) attaches a sequence number to each message. When an EWS finds that it failed to receive a telegram with a certain sequence number, it asks the sender to retransmit it. This method does not increase the server s CPU loading or the LAN loading so much. There are four independent LANs (on-line, maintenance, off-line, and general-purpose) for different types of data/applications so that message transactions of a critical type are not interfered by those of another type. Servers and EWSs The servers are Hitachi RS series control computers (main memory: 256 Mbytes, hard disc memory: 1.4 Gbytes) having a RISC (reduced instruction set computer) architecture and UNIX operating. The FEP and SCADA servers and the file servers each have a redundant configuration. The hard discs of the SCADA and file servers are mirrored discs (each 2.4 Gbyte) which can be accessed from either of the redundant servers as they have a kernel database of both on-line and off-line functions. High-performance and high-reliability RISC-type EWSs are used to provide the human interface. High reliability A redundant configuration is used for the servers and LANs. This enables instantaneous switch-over without data loss when a failure occurs. The EWSs are not designed to be redundant because there are several of them. Switch-over is handled in units of each server type, such as FEPs, SCADAs, and file servers. Application software SCADA Load flow control Fault supervision Database access mechanism Middleware Data resource management Database GUI (X Window System*) Distributed environment support Network management Basic software UNIX TCP/IP and others Ethernet FDDI GUI: graphical user interface *X Window System is a trademark of X Consortium, Inc., USA Fig. 2 Software Architecture. Software architecture to minimize effect to application software is required, even though different basic software is used.

4 Hitachi Review Vol. 47 (1998), No Table 2. Power Application Software The power application software for the new EMS/SCADA is outlined below. Phased expansion is possible. Function Outline Supervisory control and data Aacquisition Power apparatus outage scheduling for maintenance Power flow control Data maintenance Voltage/reliability monitoring Economical load dispatching Unit commitment of generator Power restoration after network failure Supervises status/changes of breakers, disconnectors, and protective relays. Inducement of charged/uncharged status of lines and buses. Supervises active/reactive power against operational/emergency limit. Judges network faults and supervises activation of block stabilizer. Estimates most likely numerical data set to represent current network by FDLS method. Anticipates hourly total loads (24 points) for 1-7 days ahead based on the weather forecast, type of day, etc. utilizing historical data about weather and load. Supports operators coordinate and schedule maintenance shutdowns for 1-36 months ahead by providing a screen display of network configuration and reliability analysis and by assembling, displaying, and modifying requests for maintenance jobs on the screen in a table. Supports operators provide effective power flow control by evaluating network reliability for each 15-minute time period for the next 10 hours, considering anticipated total load, network configuration, load flow, and contingencies. Enables operator to modify database of power apparatus and network topology by drawing single line diagrams on the screen and defining parameters. Monitors present voltage reliability and transient reliability and predicts future status some hours ahead Controls generator outputs economically according to demand considering the dynamic characteristics of boiler controller of thermal power generators while keeping ability to respond quickly to sudden load change. A suitable schedule for starting/stopping the generators for the next 1-7 days is made using dynamic programming. Presents emergency strategies to prevent network disruption just after a network fault and later presents strategies and switching operation of breakers and disconnectors to restore power while keeping network reliability. Table 3. List of Functions Functions of new EMS/SCADA are outlined. Classification Basic functions Power application software Others Content Communication for network Update current online database Data aquisition and conversion Historical data recording Alarm/event handling Data calculation Monitoring of measurement items Classification of network routes according to different power sources Inducement of charged/ uncharged status of lines and buses Judgment of network fault and activation of block stabilizer Deducing faulty power apparatus Load flow calculation/load flow optimization/network model builder Automatic generation control and economical load dispatching Load flow constrained economical load dispatching Short-circuit calculation Prediction of supply capability Trade-off between thermal and pumping generators Contingency calculation/on-line reliability calculation Sensitivity calculation Bus load forecast Displaying requests for maintenance outage in a table Human interface such as network diagram and trend graph Database generation of network diagram Data maintenance Training simulator (separate ) If a failure causes switch-over in one type of server, switch-over of other types is not necessary. Software architecture Application software is constructed in hierarchical layers as shown in Fig. 2. Its configuration is common for all servers and EWSs. Application programs can share all the data among all the servers and EWSs and can access any data anywhere through the middleware Database Access Mechanism. Programmers are thus released from the complicated procedure usually required in distributed s to refer to data and/or ensure consistency among data stored in different distributed places. Normally in distributed, the database is located only in the server and all other clients access the server. This generally causes heavy loading on the LAN and CPU of the server, resulting in a slow response of the application software and graphical user interface. To avoid this problem we introduced and developed a suitable database access mechanism for a distributed and achieved a fast response. The database of the power network model and that of on-line data are located not only on the SCADA server but also on other servers as necessary as replicas of the master database. The database access mechanism automatically keeps consistency among master/replica databases and ensures that the contents of the data are the same in all of them.

5 212 Open Distrbuted EMS/SCADA System Input data Current network Anticipated load Load Time Outage Schedule Anticipate future network Station X X X Period 10:00 Z Z Z Unit commitment schedule Station Period X X X 10:15 10:30 Contingency calculation Network reliability Proposed countemeasures to keep network reliability and suppress cost increases Z Z Z 19:45 Fig. 3 Power Flow Control Function. Supports operators provide effective power flow control by evaluating network reliability for each 15-minute time period for the next 10 hours. POWER APPLICATION SOFTWARE The power application software of the new EMS/ SCADA is listed in Table 2 and its main features are explained below. The functions of the are listed in Table 3. Seven different methods of forecasting based on linear multiple regression analysis are available. All their results are presented to an operator. Reviewing the results of load forecasting and referring to historical statistics on errors between predicted and actual loads for each method, the operator selects one of the results to be accepted. The contains empirical knowledge of cases where forecasting methods previously generated big errors in the predicted load, and it warns the operator if the pattern of parameters matches that stored empirical knowledge. Power apparatus outage scheduling for maintenance Requests for a power outage for maintenance purposes during the next one month to three years are transferred to the CLDC from maintenance-related offices on-line or manually. The power flow at the requested time is calculated based on the predicted load and predicted network configuration and the network reliability is checked. Requested/planned maintenance jobs are assembled and displayed on the screen in the form of a table. Planning engineers can then check for any duplications, combine some maintenance jobs together, and change the time of any maintenance job interactively. Power flow control (Fig. 3 ) Network power flow is calculated based on anticipated total loads, scheduled generations, anticipated network configuration, etc. for future time periods every 15 minutes for the next 10 hours (total: 40), and network reliability is analyzed based on results, which are presented to operators to support reliable network operation. The following information is presented to operators. (a) Overload status of lines and activation status of block stabilizer relays in case of a fault on one or two lines or a double fault on two lines. (b) Spinning reserve (hot stand-by generation capacity in response to a sudden increase in load) for each time slice. (c) Proposed countermeasures by changing allocation

6 Hitachi Review Vol. 47 (1998), No of required total power generation among generators in order to eliminate overloading. Network reliability is also analyzed for conditions input manually by operators by selecting some line, transformer, and bus faults. The two features of power flow control function are explained in more detail below. (a) Anticipation of load flow The anticipated total load, scheduled tie line load, etc. are input from the load forecasting results. The total load is corrected based on the actual results during the previous hour. The network configuration at each time slice is predicted referring to the power apparatus outage schedule and planned network reconfigurations. The generation schedules of hydro, thermal, and nuclear power stations are also considered. (b) Calculation of tradable power capacity As the power network of The Kansai Electric Power Co., Inc. in western Japan can trade electricity with eastern Japan to balance supply and demand, the area s capacity to trade power without losing network reliability is examined at each time slice. Information Management One of the most popular relational database management s, ORACLE* 5), is used to store information acquired by the so that it can easily be referred to later by other computers. CONCLUSIONS Our new EMS/SCADA is a full-scale open distributed using servers and engineering workstations. We will continue to upgrade its functions and expand its data storage capacity to meet new requirements. Since workstations and other components, whose performance is expected to improve in future, can easily be added to this, without replacing the whole, we believe that its lifecycle has now been extended, thus protecting customer investment. ABOUT THE AUTHORS Norikazu Toshida Joined The Kansai Electric Power Co., Inc. in Belongs to Office of Power Sytem Engineering & Operation. Currently working for upgrading of EMD/ SCADA functions of Central Load Dispatching Center. Member of the Institute of Electrical Engineers of Japan. k406149@kepco.co.jp Mario Uesugi Joined Hitachi, Ltd. in Belongs to the Power Systems Engineering Department at Omika Works. Currently working for EMS/SCADA business for overseas countries. Member of The Institute of Electrical Engineers of Japan. m-uesugi@omika.hitachi.co.jp Yuji Nakata Joined Hitachi, Ltd. in Belongs to the Power Systems Engineering Department at Omika Works. Currently working to develop EMS/SCADA. Member of The Institute of Electrical Engineers of Japan. nakata@omika.hitachi.co.jp Masaaki Nomoto Joined Hitachi, Ltd. in Belongs to the Power Systems Engineering Department at Omika Works. Currently working to develop EMS/SCADA. Member of The Institute of Electrical Engineers of Japan. m-nomoto@omika.hitachi.co.jp Tomonobu Uchida Joined Hitachi, Ltd. in Belongs to Information & Control Engineering Department, Power Systems Information & Control Div. Currently working for EMS/ SCADA business for overseas countries. to_utida@power.hitachi.co.jp REFERENCES (1) M. Yoshikawa, Y. Nakada, M. Nomoto and H. Kudo, New Energy Management System of Central Load Dispatching Center, Hitachi Hyoron 78, February, (1996), pp (in Japanese). (2) T. Nakayama, M. Nomoto, Y. Harada and M. Tsurugai, Latest Energy Management Systems, Hitachi Hyoron 80, (February, 1998), pp (in Japanese). *1) Ethernet is the registered trademark of Fuji Zerox Corp. *2) UNIX is the registered trademark of X/Open Company Limited. *3) Motif is the registered trademark of Open Software Foundation, Inc. *4) X11 is the software developed by the Massachusetts Institute of Technology. *5) ORACLE is a trademark of Oracle Corporation, U.S.A.