Tatsuji Tanaka

A remote supervisory system for a power system protection and control unit applying mobile agent technology

We apply mobile agent technology, which has attracted attention in the field of distributed software system, to a power system protection and control system. We have developed a system which can reduce the total cost of maintenance and management of protection and control equipment. We have proposed an Intranet Power System which performs supervisory control of a power system using Internet technology. We have proposed a mobile agent for power system protection and control system as part of the Intranet Power System. Although an agent is powerful in its ability to perform processing in a distributed network environment, a normal agent for business use does not offer a guarantee of operation within several milliseconds and real time performance. In this paper we propose the Real Time Mobile Agent Platform (RTMAP) which provides more powerful functions to synchronize between two or more agents in a distributed node, and redundancy to deal with unexpected communication failure. So the agent can now be applied to the power system protection and control system for which real time operation and advanced reliability are required. At present, a remote operating and monitoring system for protection and control equipment has been verified for real use and put into service. However, in order to perform maintenance or event analysis for two or more equipments, it is necessary for the operator to use the terminal (PC) for data collection and analysis, connecting and communicating each equipment individually. If we can use the agent proposed in this paper, then the information or equipment at two or more substations can be collected and analyzed automatically. Moreover if the database on a PC server performs further intensive management of data, then a full maintenance support system can be developed, and an increase more efficient maintenance work can be expected.

Distributed real-time computer network architecture-power systems information model coordinated with agent applications

The authors have defined information models for power systems and devices based on object oriented technology, and designed Global and Local information models. The Global information model is used for EMS/SCADA and power systems operation in the control center, and the Local information model represents the behavior of components and devices in the power station and/or substation. Similar information models are being developed by IEC-TC57 as IEC61970 and IEC61850, and by EPRI as CCAPI and UCA2.0, aiming for standardization of open and multi-vendor systems integrated by cooperating EMS/SCADA systems, or equipment and devices. The information models are based on those of IEC and EPRI, and they are expanded for distributed processing in network environments. The authors implemented IEC61970 as the Global information model and IEC61850 as the Local information model with Java Class library. Also, the authors developed a prototype system that consists of a personal computer (PC) as control center, and 2 PCs as substations, and a network computing terminal with current and voltage sensors as another substation. The authors implemented agent applications for simple SCADA and simulation of the power systems devices (ex. Power Transformer, Circuit Breaker) to evaluate the cooperation between agent applications and the information model, and proved the usefulness of the information model. The authors examined the functional expansions for distributed environments, and clarified their ease of implementation and effectiveness.

Network integrated supervisory control for power systems based on distributed objects

This paper proposes a new architecture called SCOPE (System Configuration Of PowEr control system) for flexible supervisory control of power systems. Energy Management Systems / Supervisory Control and Data Acquisition (EMS/SCADA) systems are usually widely distributed and have hierarchical operational organizations. They are continuously changing in accordance with various requirements and environments. Therefore, they need to be flexible enough to quickly adapt to those changes. SCOPE classifies software for conventional electric power systems into three hierarchical layers, the Application dependent part, the Power system dependent part and the Computer system dependent part. The power system dependent part realizes flexibility for changing of power system equipment and operational organization by introducing a reduction relationship which enhances the generalize/specialize relationship of object oriented technology. SCOPE architecture enables EMS/SCADA systems to be flexible, and also enables efficient and economic development. It is confirmed through developing and evaluating a SCOPE prototype system that the flexibility of EMS/SCADA systems is improved.

Decentralized autonomous object-oriented EMS/SCADA system

Energy management systems/supervisory control and data acquisition (EMS/SCADA) systems are usually geographically distributed and have operational organizations. They are changing in accordance with the various and varying environments, and they should be flexible enough to adapt to those changes quickly. The paper proposes a new architecture called SCOPE (System Configuration of Power Control System) to realize flexible and reliable EMS/SCADA systems. SCOPE makes application programs independent of the operational organization and system configuration of the EMS/SCADA system, i.e., application programs are not influenced by changes in them. These properties make EMS/SCADA systems flexible and reliable, and also the development of EMS/SCADA systems becomes efficient and economical. Through developing and evaluating a SCOPE prototype system, it has been confirmed that the flexibility and maintainability of EMS/SCADA systems based on the SCOPE architecture has been improved.

Verification of Distributed Real-Time Computer Network Architecture Associated With Off-The-Shelf and Dedicated Technologies

This paper introduces an architecture for computer communications applied to the operation and maintenance of power systems, the distributed real-time computer network architecture (DRNA). The architecture consists of four functional entities, namely, application programs associated with information models, an adaptation function, a transport function, and network- and security-management functions to achieve seamless, real-time, adaptive, and secure information exchange between distributed power system control devices. DRNA uses off-the-shelf and standardized technologies along with dedicated ones. Through careful application of the technology, an experimental setup of a distributed cooperative voltage-control network was constructed in a power system simulator to verify the architectural concept. The implemented technologies include mobile agents, middleware for prioritized and redundant communication schemes, label-switched and Ethernet-based transport networks, and a secure virtual private network. The experiment demonstrated the effectiveness of DRNA.

Evaluation of object-oriented database for distribution network monitoring system

This paper outlines an original object-oriented database management system which is designed for industrial applications and describes results of an experiment to apply it to a graphical user interface in a power distribution monitoring system. Database management systems are widely used and achieve high productivity and high reliability of data management in the business field and in some engineering areas. However conventional database systems, especially relational database systems, are rarely used in industrial real-time fields. This paper presents advantages of object-oriented concepts for modeling complex data of a monitoring system. The object-oriented database successfully supports data-modeling requirements of GUI applications, and the performance is well acceptable for GUI applications.

Object-oriented database management system for process control systems—development and evaluation

This paper presents an object-oriented database management system designed for industrial applications, and describes experimental results in applying it to a power supervisory control system. Database management systems achieve high productivity and high reliability of data management in the business field and in some engineering areas and are widely used. However, conventional database systems, especially relational database systems, are rarely used in industrial real-time fields. For example, power supervisory control systems require a high performance database system which uses a complex data structure. In such systems database systems must be able to retrieve and up date information within a limited time (e.g. less than 166 msec). It is difficult for relational database systems to manage complex data structures and to achieve the performance needed for real-time process control. We have developed a compact and high performance object-oriented database system “Odb” for process control systems. We propose a data model which integrates a set of objects which belongs to the c!ass and a set defined by the user. We have also developed an architecture which provides uniform access to persistent objects and transient objects, and an efficient implementation method. We present the data model, the database language and the architecture of Odb, then show advantages of object-oriented database systems applied in power supervisory control systems. Permission to make digital or bard copia of ail 01 prrt of Ihis Wok for persod or classroom use is gruacd without fee provided tht copies are not made or distributed fa prolii oc COIN’II~~ advantage and that copies bear this notice and the full citalion in the first page. To copy othcrwisc, to republish, to posl on scrws 0~ to redistribute to lists. requira prior specific pcnnissian ~MUW a fee. SAC 9, San Antonio. Texas 01998 ACM I-581 13-086-4/99/0001 S5.00 INTRODUCTION Computer systems for plant supervisory control must be reliable and react responsively. Database management systems are widely used and achieve high pm ductivity and high reliability of data management in the business field and in some engineering areas. However conventional database systems, especially rels tional database systems, are rarely used in industrial real-time fields. Conventional database technology has some shortcomings as follows [2, S]: l The data model is too simple for modeling complex nested entities. l Data types are limited. 0 Semantic concepts are lacking. l The response of relational database ss&ems is unacceptable for real-time systems. l Database languages (SQL) are very d&rent from programming languages, in both data model and data structures. This problem is known as impedance mismatch. Many commercial object-oriented database management systems (OODB) are available now. However, most of them have a lot of unnecessary features and can not easily achieve the response needed for real-time process control. Compact and responsive OODB are required in the field of industrial systems. Therefore, we developed “Odb” with the following features for real-time protest control applications. (1) Support of object-oriented concepts (2) Quick response and high performance (3) NO impedance mismatch In the next section, we present the data model, the database language and the architecture of Odb. The third section shows advantages of object-oriented database systems applied in power supervisory control systems. The results presented in the fourth section. OBJECT-ORIENTED DATABASE Odb This section describes the functional specification of Odb. Odb has the following features [4]. (1) Support of object-oriented concepts Odb supports all object-oriented concepts, such as Encapsulation, Classes, Inheritance, Polymorphism and Overloading. It also provides extent[3] and built-in Collection (Set and Bag). The extent is the set of all instances of a class and the Collection is a set of objects specified by a user. (2) Quick response and high performance Odb is a compact and efficient database system that has adopted the client/server architecture. The Odb database engine adopts pointer swizzling at page fault time technique to translate the object identifier of an object to virtual addresses. Furthermore, Odb provides clustering. indexing and client cache mechanisms. (3) No impedance mismatch To achieve high productivity, Odb provides C++ based data-base language, The user can define a database schema as a class definition, and can make, store, and retrieve persistent objects in the same way as non-persistent objects in C++. Odb is designed for real-time use. Therefore, we simplified the functions which commercial OODB supports and attempted to produce high performance by using a concise functional specification.

Power systems information delivering system using Internet technology

Computer network technology and distributed information processing technology have been developing rapidly. In the meantime, deregulation is starting and will be spreading in the electric power industry in Japan. Consequently, customers request low cost power supply and high quality services from the power suppliers. Corresponding to these requirements caused by deregulation, the authors developed a prototype power systems information delivering system supplying useful power systems information such as power failures. The prototype system was developed based on SCOPE (system configuration of power control system) architecture that we had already proposed. SCOPE architecture assures flexibility and scalability for power systems. The prototype system consists of an application layer based on a Web browser, an information model layer which reflects the power systems behavior and a distributed object management layer using CORBA and OS/Network layer. In this paper, we introduce the concept, functions, implementation of the prototype system and its evaluation results.