1 BACKGROUND
1.1 Introduction
Recently, utilities have witnessed a strong trend towards new standards and tech-nologies, fundamentally transforming their capabilities and bringing a new solu-tion that supports and meets their existing and future demands. However, exist-ing power systems’ automation and protection have traditionally used proprie-tary manufacturer-specific communication protocols carried over other protocols for various applications. According to these infrastructure interfaces among pow-er system nodes, intelligent electronic devices (IEDs) from various manufacturpow-ers may require huge investment based on developing a costly and complicated pro-tocol convertor. Consequently, conditional power quality supply has been high-lighted in recent years, and new laws, taxes and deregulation have been issued for instance, in Finland penalties have been regulated for non-delivered energy, while Sweden has issued a new law such that no interruptions longer than 24 hours are allowed after the year 2011 (Brändström & Lord 2009). Therefore, one of the most dominant considerations of current and future power system design comprise the standardization solution, product-featuring, smooth integration and a higher degree of adaptability, such that it may be used to revolutionize power systems’ operation, improving reliability as well as maintenance, and re-ducing the installation time and effort. In order to address these issues, in 2003, the International Electro-technical Commission (IEC) Technical Committee (TC)-57 has published the IEC 61850 standard, entitled “Communication Net-works and Systems in Substation” (IEC 61850 standard), which is defended as a common inter-national standard and one of the most promising powerful solu-tions to existing power industry limitasolu-tions, and which is expected to support power systems’ evolution. As far as the IEC 61850 standard is concerned, it is a promising solution to existing power systems’ limitations; however, various
as-pects are not specified within the IEC 61850 standard and are left for end-use for instance, the highly reliable substation automation system (SAS) communica-tions bus topology, types of redundancy, etc. Moreover, researchers and develop-ers have noted that the open nature of the IEC 61850 standard gives broad free-dom for manufacturers to operate with. Further, the interpretations of the IEC 61850 standard from different manufacturers remain different based upon the ambiguity that still exists. These issues may vary the interoperation of the stand-ard from one manufacturer to another and may increase the complexity of the interoperability tasks within the SAS. In addition, many of the available automa-tion and protecautoma-tion funcautoma-tions are grounded upon the emerging concept of a smart grid (SG) based on the IEC 61850 standard are whether need to be developed, or initially invented in which that softly amendment solutions are no more feasible.
This is because several principles of conventional power systems, such as the ra-dial topology, passive nodes, one-way power flow, etc., are not maintained any-more. Therefore, further discussion and testing works need to be processed, and revolutionary energy system infrastructure changes might need to be based upon the IEC 61850 standard in order to meet end users’ requirements and prove the feasibility of the IEC 61850 standard (i.e., that it possesses high-energy system reliability and is fault-tolerant).
Meanwhile, the global acceptance of the IEC 61850 standard has raised its profile as an interesting area of research, from both the academic- and the industry-side.
This wide acceptance has stimulated researchers and developers to go further to-wards plug-and-play-based IEC 61850 implementations within SAS and beyond to an SG. For coping with these demands, various research groups and pilot pro-jects have been carried out globally - for instance, the University of Vaasa has set-up an in-house research and testing laboratory, the Development of Education Services of IEC 61850 in a Multi-Vendor Environment (DEMVE). All my re-search activities have taken place under the umbrella of two projects, namely DEMVE I and DEMVE II. These projects raise the vision and the spirit of the IEC 61850 standard based on sharing data among various manufacturers’ intelligent electronic devices (IEDs) and executes the information that has been shared by this data (i.e., interoperability). Interoperability is one of the main concerns re-garding the IEC 61850 standard. Moreover, it has also been considered as the major challenge faced by SAS design engineers in establishing seamless commu-nication among various manufacturers’ IEDs. However, initially, substation au-tomation and protection was the main focus of the IEC 61850 standard’s first version. The key point is that it provides a uniform framework for all the related system levels. IEC 61850 takes into consideration all the various aspects that are common at the substation site, such as data models, communication solutions, engineering and conformity testing. The legacy protocols concentrate on how the
data is transmitted on the channel. Meanwhile, it organizes the data - in terms of applications - by means of syntax and semantics in the devices where they do not specify it. The main aspect that IEC 61850 adopts based on its architectural con-struct is “abstracting” the data object’s definition and services. Independently of any underlying protocol, it creates data objects and services that support a com-prehensive set of substation functions and it provides strong services to facilitate substation communication. The abstract definitions of the data object allow its mapping to any protocol that can meet the best data and service requirements, as IEC 61850 does not specify any protocol. IEC 61850 specifications focus on three major issues, namely standardizing the available information, services (write, read, etc.) and communication services. Further, the IEC 61850 standard in Part 8 and Part 9 (IEC 61850-8; IEC 61850-9) specifies Ethernet communication technology based on the open system interconnection (OSI) model for the station and the process level within the SAS. Ethernet technology has been defined as an appropriate communication solution for power automation usage based on its high flexibility, bandwidth and speed.
This thesis provides guidelines and facilitates the design and implementation of the IEC 61850 standard within an SAS. It first considers the relatively new IEC 61850 standard from different perspectives. An explorative study and analysis of the IEC 61850 standard and the legacy power system are conducted which demonstrate the impact of the IEC 61850 standard on the legacy power system’s infrastructure, such that it might not meet the requirements imposed by electrici-ty utilities’ deregulation. Furthermore, various reliabilielectrici-ty and availabilielectrici-ty analyses have been carried out on different SAS communications bus topologies. Secondly, several practical testing experiments for the SAS based on the IEC 61850 stand-ard are designed, constructed and carried out. These practical testing experi-ments are implemented to evaluate and prove the feasibility of the IEC 61850 standard as a promising solution for the communications system within the en-ergy system. Lastly, a favorable communication solution based on a new commu-nication technology, cognitive radio (CR), for a future SG is proposed. Strong practical experience was gained through the SAS configuration process, several contributions were made based upon these analyses and some future work issues were identified (more details about these contributions are presented in Section 1.6).