MODERN-PLANNING TOOLS CONNECTED WITH GEOGRAPHIC INFORMATION SYSTEM IN UTILITY COMPANY Vybiralik Frantisek STE - Stredoceska Energetika a.s. - Czech Republic fvybiralik@ste.cz Josef Tlusty Technical University in Prague Faculty of Electrical Engineering - Czech Republic tlusty@feld.cvut.cz Vladimir Pavlicek Daisy s.r.o. Czech Republic pavlicek@daisy.cz The geographic information system is a modern information system that contains information about customers, network configuration, switch status, inventory, system maintenance. Engineering operations and planning departments can rely on data in GIS. The data are reliable and good managed. It enables the engineer to do his work more effectively. Engineers can perform load-flow analysis, reliability study, customer outage prediction or economic analysis with the GIS. Planning Engineering can works with the GIS to execute detailed prospective of the network development. Engineers working in operations departments can evaluate switching procedures to change from the existing state to new state. They find weak network points and predict network component overload. This sophistical product supports distribution system analysis and simulation. The distribution model is built from database objects in the GIS. INTRODUCTION The network geographic information system is a planning and documentation system for electricity distribution networks containing systematically stored technical, economical and location data about existing and planned networks. Its primary purpose is to support the management of distribution system including planning, design, construction, operation and maintenance functions. It thus supports a utility s day-to-day operational and medium and long-term decision making processes. Every distribution network company has some sort of a network information system. For different utilities the optimal system is obviously different. It depends for example on the following features of the utility: - number of customers and area of distribution - housing density of the distribution area - structure of the consumers - management and organization. The network activity (distribution of electricity) still remains monopolistic and regulated but costs must be reduced and the relevant backup information is made available to government officer regulator. All of these business activities can be effectively supported by an advanced network information system. IMPROVEMENT STAGES Alphanumeric system The first step was to collect data about the circuits and load and make it possible to calculate radial load flows and fault currents. These were separate technical applications but very soon they were combined with the record-keeping systems to develop the first network information system utilizing a common database. Usually these were run in a batch-processing mode in the utilities mainframe computers or in commercial data processing centers, typically once or twice a year. Line, node and transformer files need to be established for technical calculations. These define the configuration of the network and include technical information for the various network components. Typically, the outputs of these systems consist of long lists of plant data and calculation results because map information has not been included. Most applications now used in utilities are still alphanumeric and the lack of graphics limits their flexibility. This type of network information system is often called a facilities management (FM) system. Graphic network information system The system has an interface showing the geographic background and network maps. The display often also includes several windows where alphanumeric information on different object is displayed. Graphic and alphanumeric data can be updated at the same time and the attributes of different objects may be linked to scanned image such a photographs or drawings. The characteristics of the objects may be different in different wives having, for example, a different scale. Numerical results can also be displayed linked to the network map and different colours in line sections or nodes can be used to indicate, e.g. voltage drops, levels of load and levels of fault currents. These systems are often called AM/FM (facilities management/automated mapping) systems or AM/FM-GIS systems (geographic information system). STE_Vybiralik_A1 Session 5 Paper No 61-1 -
INFORMATION SYSTEM COMPONENTS Database management system and application programs A database system consists of a database, a database management system and application programs. The system includes also the necessary hardware. The database is the most valuable part of the system, since it is core of the stored and linked data. Data are stored or updated in the database only once and the same data are available for various applications and users. This is a very valuable feature because it prevents the existence of different parallel updated data. The database software is a general program that is used for managing and handling the data stored on disk. At present the most important class of database software is a relational database. These databases consist of tables and each object in a data model, for example a distribution substation or circuit breaker, can form a table. Links between tables are formed during enquiries. In this way each piece of information is stored in one location only and any set of related data can be easily retrieved simultaneously. The user can make enquiries to the database flexibly by using the Structured Query Language SQL. Relational databases are flexible as regards revision and developments to the network information system and are also well standardised which supports data exchange and linking between systems. When using a database system it is possible to apply the same interface program for many applications. This makes the development of applications more efficient. For the user it is convenient when all applications have similar interfaces. When application programs are separate from the data, new applications can be added without necessarily affecting the configuration of the database. Contents of database For a utility most of the overall costs related to its network information system are concerned with the establishment and upkeep of its data. The main groups of data are network and plant data for day-to-day operation, work information and customer data. They include, for example data related to the following items: - construction, location and maintenance of HV, MV and LV networks - topology and connections between networks and substations - fault and measurements - consumption and loads including load curves for customer groups - customer and delivery points - switching programmes, switching-state changes and measures data. The most important data transferred from other systems to the network information systems are: - customer information system: delivery point, customer and consumption - SCADA: state changes of switches and measurements - national and municipal geographical information systems: background map with attributes Application programs, especially those for technical functions, need network graphics for user interface, with both maps and diagrams. Different available views may be: - a location map at scale 1:500 to 1:2000 for LV network map - a general map at scale 1:10 000 to 1:50 000 for MV and HV network map - a schematic map for operational purposes of the MV and HV network The above-mentioned schematic map shows the configuration and switching state of the network and therefore is often the optimal choice for the interface in planning and maintenance activities. The general MV and HV network map is suitable for the interface in technical calculations and in the management of the switching status, especially outside city areas. Alternatively, the schematic version can be used for the later purpose. The network database includes information for each line section of MV, HV and LV networks, substation data, transformer and switchgear data and other technical data. The load data of the existing customers are transferred from the customer database to the network database. The load data of the customers are set with transfer an annual consumption to the load. Each customer has a customer group code and tariff. Database management AM/FM systems have two separate databases: a graphic database and alphanumeric database. These are linked with each other. Graphic information can be represented either in vector or raster mode. In the vector mode the coordinates of the ends of section present a line section and the line type is known. In the raster mode a figure consists of pixels and their value gives the colour of the area element. Digitising network maps with digitising tables usually forms vector data, while raster data are produced with scanners, which form digitised file. In many of the developed network information systems the concept of one common database is applied. Only one relational database is used both for graphic and alphanumerical data. From the utility s point of view a system with a common relational database is useful. Most utilities have the knowledge for operation and connecting new interfaces to a relational database and are able to manage and develop the system. When a large number of applications programs have been implemented, even for a smaller utility the database may include hundreds of tables. The size of background map files outside the database may be up to several gigabytes. Application programs A modern network information system can include a large variety of application programs, which support the management and development of the electricity distribution system and utilise the same database and graphic interface. Programs for planning and design networks, construction STE_Vybiralik_A1 Session 5 Paper No 61-2 -
and maintenance network components and for operating of the networks have the main meaning. A GIS system offers an effective and rapidly developing environment that can be used on more and more new applications. They can effectively support other graphic-related functions of the utility. In particular, the versatile capability for utilising geographic, network-map and substationscheme information offers many possibilities for design, operation and customer service. Network calculations In a FM system use in the monitoring, design and planning of distribution networks, various results describing either the present or future state of the system are calculated. These results include power flows, power and energy losses, drop voltages in the network, fault current and reliability indices. The load flow of interconnected distribution network is calculated with the Newton-Raphson load flow method. The output from the load flow program consists of: - real and reactive power flows and real and reactive power losses in each feeder section - voltage at each node of the network - load current in each feeder section. Analysis of fault currents enables the operation of various protection systems to be assessed. The 3-phase, phasephase and phase-earth fault currents are calculated. The maximum 3-phase fault current is important for checking the capacity of cables, overhead lines and other network components to withstand the fault current. The minimum fault current is needed when checking the sensitivity of the protection. Reliability studies are usually carried out for the MV networks since the main proportion of the outages experienced by a customer is due to the faults in the MV network. They also produce various reliability indexes, such as interruption/customer/year. For planning purposes is convenient to compare the reliability of the network with standards. The outage costs are thus calculated applying the value of nondelivered energy. Its value is base on customers opinion of the inconvenience caused by the interruption. In the network monitoring function of the network information system the load flow and fault currents are calculated for whole network of the utility. This is usually carried out once or twice a year. In the expansion planning of distribution networks the network-calculation modules have two functions: - to provide the data needed for the calculation of the costs - to provide the data needed for checking that all the technical constraints have been achieved The calculation modules can also assist in various operational tasks. If the network information system has a connection to the SCADA system, for example, on-line load flow studies can be carried out. In an on-line study the current state of the system is simulated so that the calculations made with the aid of load curves are corrected using available measurements. The results can be used in estimating the effects of switching actions. The calculations needed for these tasks are only possible with the aid of load curves defined for the whole year. Another important benefit of the connection between the network information and SCADA systems is the real-time information received about the states of switches so that the calculation can always be made using the actual switching configuration. A modern network information system includes modules for distribution network planning. For this purpose interactive design programs may be used, where the main tasks of the program are the calculation of the costs and checking the technical constraints. The planner makes the design of different possible plants and the comparison of costs. The network-planning task can be formulated as an optimization problem where the object is to minimize the costs while taking into account the technical constraints. The objective function contains not only the investment costs, but usually also cost of losses, costs of outages and operational and maintenance costs. The constraints are also used for verifying that the solution satisfies safety regulation, thermal capacities of the network components, voltage drop limits and operational requirement for the protection. GIS APPLICATION IN STE In 1994 the specification process of the network information system application started in STE. The main idea was not to develop a traditional network information system for documentation and technical calculations for the existing network but to provide effective support for day-to-day operation matters. In the first phase was collected data for all network components: overhead lines, underground cables, transformer stations, switchgears and other equipment. The data collection of the MV and HV networks lasts five years. Technicians had to check the technical documentation and compare it with the real state. The documentation in paper form was transferred manually into digital form on the special workstations. Our company provided digital maps in raster at scale 1:10 000 for the whole STE supply region. Digitizing the location maps in scale 1:1 000 or 1:2 000 was provided the town maps. Operational and development technicians can use this GIS. They can display and print technical documentation of the power lines and transformer station from the selected area simultaneously with background map and aerial picture. Special viewer program is not necessary for display any information from GIS. Internet Explorer is used as the viewer for maps and technical documentation. PROGRAMS FOR NETWORK CALCULATION APPLICATED IN STE Programs for network calculation were developed by the STE_Vybiralik_A1 Session 5 Paper No 61-3 -
software house in cooperation with Technical University in Prague Faculty of the Electrical Engineering. There are two basic programs. Program PAS On-Line is intended for operative power networks management and program PAS Off-Line is designed especially for planning of the development, design and long-term preparation of MV and HV distribution networks. Network calculation with program PAS Off-Line PAS Off-Line uses the data, which describe the parameters of the modeled electricity system stored in the GIS database, and also uses the imagines prepared by GIS. The ability to cooperate with GIS systems, based on LIDS technology is yet another big advantage. The transfer of the MV network scheme in GIS to scheme in PAS Off-Line is presented in the fig. 1 and 2 on the next page. Though GIS PAS Off-Line can access the information on wholesale customers and the data on regular consumption measurements. In the future, it will be possible to store the data and images back to GIS database. If required, it is possible to create an interface to other systems operated by the customers, provided that the systems provide the data in a suitable format, which can be analyzed. The program includes the following features. It enables easy creation and modification of network diagram in an objected-oriented graphical environment with automatic creation and maintenance of data images. The database is created as the image is created. The resulting network diagram can immediately be used for calculations. The data stored in PAS On-Line and SCADA systems can be easy connected. Program enables analysis of steady-state load flow using full mathematical model with no simplification of the standard mathematical methods, which could mislead the user, especially during the calculation of limit states. Network elements are color-coded in dependence on their connection to the power source. Program carries out analysis of short-circuit conditions in the network: full calculation of symmetrical, unsymmetrical and multiple faults, including the data for protection setting. The planner can make test of the effects of planned changes to the network. He can consider load of lines and transformers, level of transmission losses. He can create of consumption trends with the possibility to categorize the trend by areas. Network diagrams are color-depending on the topology, load of line, voltage distribution in the network, losses, short-circuit conditions, quality of the values, relative current, protection. Other visualization types can be added on customers request. Results can be printed in both the table report and graphic format. The color printouts maintain all the information visible on the screen. Big network diagrams can be plotted using big format color ink-jet plotters. MV network study in STE This program was used for MV network in supply area of STE in Central Bohemia. MV network is divided to four parts. Every part of the network is managed by the Regional dispatching center. MV network in one region includes about 2500 km overhead lines, 250 km underground cables and 2000 substations MV/LV. The existing network was checked with full analyze: load flow, short-circuit currents, voltage drops, transmission losses, contingency analysis. The network development phases were studied. A realistic option is the construction of a new 110/22 kv substation and new 22 kv feeders. REFERENCES [1] E. Lakervi, E.J. Holmes, 1996 Electricity distribution network, Peter Peregrinus Ltd., London, United Kingdom, 273-290 [2] J. Holinsky, F. Vybiralik, 1998, Modern calculation systems for planning of the distribution networks, Conference CK CIRED, 6/48-6/53 STE_Vybiralik_A1 Session 5 Paper No 61-4 -
Fig. 1 Scheme of the MV cable network in GIS Fig. 2 Scheme of the MV cable network in PAS Off-Line STE_Vybiralik_A1 Session 5 Paper No 61-5 -