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Electric public-service corporations have a demand to maintain a comprehensive and accurate stock list of their physical assets, both as a portion of normal service proviso ( widening the web, set abouting care, etc. ) and as a portion of their duty to inform 3rd parties about their installations. Complexity of electrical distribution power system is a good ground for presenting new information engineering - GIS ( Geographic Information System ) that carries out complex power system analyses ( e.g. , mistake analysis, optimisation of webs, burden prediction ) in acceptable sum of clip.
By utilizing modern GIS, in concurrence with his ain in-house developed package, in less clip and more accurately, the public-service corporation applied scientist is able to plan and to analyse electrical distribution web. This paper presents the thought of the undertaking CADDiNA© ( Computer Aided Design of Distribution Network ) presently under development at the Power Systems Department of the Faculty of Electrical Engineering, University of Zagreb.
One of the primary part to the promotions and betterments in adult male 's life-style over the old ages has been the ability to utilize and command energy.
Man 's usage of energy can be seen in mundane operations such as mechanical gesture and the production of heat and visible radiation.
Large sums of power are generated at power workss and sent to a web of high-voltage ( 400, 220 or 110 kilovolt ) transmittal lines. These transmittal lines supply power to medium electromotive force ( e.g. 10 or 20 kilovolt ) distribution webs ( distribution primary system ) , which supply power to still lower electromotive force ( 0.
4 kilovolt ) distribution webs ( distribution secondary system ) . Both distribution web lines supply power to clients straight. Therefore, the entire web is a complex grid of interrelated lines. This web has the map of conveying power from the points of coevals to the points of ingestion.
The distribution system is peculiarly of import to an electrical public-service corporation for two grounds: its propinquity to the ultimate client and its high investing cost. The aim of distribution system planning is to guarantee that the turning demand for electricity, with turning rates and high burden densenesss, can be satisfied in an optimal manner, chiefly to accomplish lower limit of entire cost of the distribution system enlargement. Therefore, the distribution system contriver partitions the entire distribution system be aftering job into a set of subproblems that can be handled by utilizing available, normally heuristic methods and techniques [ T.Gonen, 1986 ] .
The design of electrical distribution webs is an mundane undertaking for electric public-service corporation applied scientists, specially in R & A ; D section. Such design was carried out few old ages ago manually. This classical attack normally result in overdesign distribution system, which is now considered as a waste of capacity that can be used alternatively of puting in system enlargement. Four old ages ago a Personal computer plan bundle ( CADDiNA© ) for optimum planning of distribution web was put in operation in Elektra - Zagreb ( Electric Utility of City of Zagreb ) . It is a consequence of joint R & A ; D of Power System Department of Faculty of Electrical Engineering and
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Elektra - Zagreb. Based on the experience or PC-CADDiNA© , at the terminal or 1992. the paradigm of new undertaking CADDiNA© was started conceptually organized as a portion of the Geographic Information System.
Database plays a cardinal function in the operation of planning, where analysis plans form a portion of the system supported by a database direction system which shops, retrieves, and modifies assorted informations on the distribution systems. The thing that distinguishes an electrical public-service corporation information system from an other information system - such as those used in banking, stock control, or paysheet systems - is needed to enter geographical information in the database. Electrical public-service corporation companies need two types of geographical information: inside informations on the location of installations, and information on the spacial interrelatednesss between them. The integrating of geographically referenced database, analytical tools and in-house developed package tools will let the system to be designed more economically and to be operated much closer to its bounds ensuing in more efficient, low-priced power distribution systems. Extra benefits such as improved stuff direction, stock list control, preventative care and system public presentation can be accomplished in a systematic and cost-efficient mode ( Z.Sumic, et Al, 1993 ) . Before graphical workstations were developed, many electric public-service corporations have built proficient information systems based on relational database direction systems ( E.Jorum, et Al, 1993. ) . Technical information system is designed to cover the demands of power supply public-service corporations sing web enlargement and operation planning, care direction and system certification. In advanced public-service corporations all information systems are built around same RDBMS and invariably updated. Establishing links between these information systems and geographical information system is merely in specifying relationship between objects in the two systems. The job that has risen is in a figure of different information systems in the same public-service corporation ( proficient information system, client information system, etc. ) or even several overlapping proficient information systems and some of these are non updated.
The aim of the distribution web design procedure can be divided into three independent parts. These parts are:
1. load growing of the geographical country served by substation ;
2. finding of burden magnitude and its geographic location ;
3. client burden features ;
Design of secondary system ( low electromotive force distribution web )
4. optimum substation allotment and transformer size ;
5. secondary circuitry routing and size ;
Design of primary system ( average electromotive force distribution web )
6. optimum substation allotment ;
7. primary circuitry routing and size ;
To cut down a job complexness each portion of the design procedure is divided in functional subproblems. Each of these subproblems can be so much easier to pull off. Although merely independent some parts of design procedure interact, i.e. arrangement of substation will act upon secondary routing which in bend will act upon primary routing. The figure of possible design solutions that might fulfill a given set of spacial, proficient and economic restraints is rather legion. Multiple, mutualist ends and restraints make conventional procedural optimisation methods inappropriate for distribution web design. Due to the complexness of the design procedure, heuristic methods and AI techniques must be applied to happen `` near optimum '' [ S.Krajcar, 1988 ] or `` hearty '' solutions [ Z.Sumic, 1993 ] . The chief ground for this simplification is sing work-force and computing machine clip for happening optimum solution that in high per centum could non be applicable in existent state of affairs.
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Pilot-project CADDiN was started at the beginning of 1993 as a research undertaking inside the chief research undertaking `` Research and Development of Electric Power System '' supported by the Ministry of Science and Technology of the Republic of Croatia. The development of optimisation and design processs of electric distribution web is a parallel procedure with edifice database by Cadastral Office of the City of Zagreb, and hence some other available illustrations of basic map databases are used for research intents ( see Figure 1 ) . The scheme employed emphasized merely the informations composed of basic map databases for proficient applications ( graduated tables of 1:500 to 1:5000 ) .
There is no alone definition for Geographic Information System ( GIS ) but a normally recognized one is that it is a system with computing machine hardware and package maps for the spacial information input, storage, analysis, and end product [ T. Bernhardsen 1992 ] . Many text edition definitions go farther and place analysis as the one activity which differentiates GIS from other computer-based systems for managing geographic informations, such as machine-controlled mapmaking.
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Modern GIS, shops information on the geometry, properties and topology of geographic characteristics in one relational database direction system. SYSTEM 9 used in the pilot-project CADDiN is a feature-oriented GIS which organizes geography-related information into a topology-structured, object-oriented, relational database system.
A undertaking is the highest degree of informations organisation of GIS used in CADDiN [ Computervision, 1992 ] . It represents the full database that has been set up for a peculiar geographic country - for illustration, a town, a municipality, or a service territory. It comprises two constituents: a information shop that contains all the geographic and attribute informations associating to characteristics ; and a database definition that specifies the construction of the undertaking through characteristic categories and subjects.
Theme definition determines which characteristics and properties are to be used and the ways in which are to be displayed. Independently stored geometry of a characteristic, and its in writing representation enables place and representational informations to be changed without mention to each other. The nexus between the geometry and the representation is provided by the subject. It comprises a list of characteristic categories, characteristic category attributes, and a nexus to a separate list of in writing transforms.
An of import safety facet of used GIS is that it does non let users to do alterations to the database at undertaking degree. A user may merely question it. The database is created and updated by agencies of the following lower degree of informations construction: the divider. This is a copied, working subset, or part of a undertaking. It is at this degree that a user interacts with the system to come in, edit, update and manipulate informations. Partitions are extracted from a undertaking based on the type of work to be done and the information that will be required to execute that work. When redaction is completed, the divider is merged into the undertaking database, set uping the update. Partitions are created by agencies of a divider definition that describes the spacial extent, the contents, and the representation. The system uses the divider definition to pull out the needed geometric and property informations and so allocates them into the needed divider. The virtue of the divider construction is that it allows different sections within an organisation to work safely on the information from the same undertaking.
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All geometric characteristics in the informations theoretical account are built up from geometric primitives, referred to as nodes, lines, surfaces and spaghetti. A node is stored as a set of X, Y, and optionally Z co-ordinates in 3D database, and might be used to stand for e.g. transformers, switchgears, MV - LV coachs, etc. A line primitive is a geometric component defined by two end-nodes ( leting intermediate points ) , and might be used to depict transmittal lines, overseas telegrams, etc. A surface consists of one or more line sections that together organize a closed polygon. A wood, lakes, Parkss, a part of web, or country covered by a batch of edifices could be described by this sort of polygon. Spaghetti enables to pattern characteristics where no topological construction is required. Nodes are the lone geometric primitives that have coordinate information straight associated with them. Lines are non defined in footings of geographic co-ordinates, but by arrows to their topological nodes. Surfaces are defined by arrows to the lines environing the surface. All these arrows are created and maintained automatically.
Geographic objects are stored as aggregations of nodes, lines, surfaces or spaghetti, but they can be referred to as geometric primitives every bit good as some group of objects which can be identified and named in the existent universe - 'roads ' . 'cables ' , 'transformers ' , edifices ' , and so on. These classs are represented by `feature categories '' , and the single cases of geographic objects as `features ' . Such characteristics at last consist of one or more geometric primitives. All characteristics within a peculiar characteristic category will hold the same topological construction, and the same set of properties.
Feature categories could be besides identified as objects in groupings of related objects that may be established on the footing of location, spacial relationships or common properties. These logical groupings of characteristics are called complex characteristics. They are defined as characteristics that contain other characteristics. All complex characteristics of peculiar type, consist a complex characteristic category. A utile application of complex characteristic categorization would be in organizing logical groupings such as MV coach, transformer, LV coach, protection devices into 'substation ' . Complex characteristics can besides hold properties associated with them ( for illustration name, figure ) . It would extinguish duplicating of characteristic properties which decently relate to the substation. Definition of complex characteristic is non restricted to include merely simple characteristics as constitutional constituents. For illustration, 'distribution web ' could be defined as a complex characteristic incorporating a figure of 'substations ' , 'cables ' , which are themselves complex characteristics.
A strength of this attack is that it can be used to minimise the degree of informations redundancy of both property and geometric information. Users interact with the database via an object animal trainer, and they are assisted in that interaction by a structured question linguistic communication that incorporates extended spacial and mention operators.
Behind analytical tools available indoors GIS environment, a set of standalone maps is available from UNIX shell. This set of maps is called Application Tool Box ( ATB ) . ATB offers an environment in which informations can be managed straight, without first holding to pull out intending from map representations of those informations. Under this attack a user can develop analytical theoretical accounts harmonizing to specific demands by integrating of ATB maps, in-house developed package ( C and FORTRAN plans ) and shell scheduling. To rush up complex analysis by Development Libraries of ATB new treating maps of ATB could be developed. Applications of undertaking CADDiN are developing by ATB maps in concurrence with C and Corn shell plans.
ATB informations direction and sing comprise processing maps, dataflow direction and artworks sing system. Processing maps perform the existent analysis operations on sets of informations called information flows, each of which corresponds to a relational tabular array in the database. All use of informations flows takes topographic point in a particular impermanent work country called a clipboard. Processing maps involve the undermentioned operations: information direction ( i.e. choosing information from database and puting it into a dataflow, pass oning with external package bundles ) , attribute processing ( i.e. bring forthing values for properties based on categorization regulations or expression ) , geometry processing ( spacial maps - brotherhood, next, etc. ) and arithmetic processing ( i.e. ciphering the country of surface entities, or length of additive entities ) . Dataflow direction is used to make, show and delete information flows and positions. Graphic sing system allows user to see the intermediate or concluding consequences and bring forth a secret plan of those consequences.
Compatible to ATB maps are standalone maps of Network Trace Analysis faculty. By those maps web following can be carried out utilizing the information on web connectivity and constituent features that are already stored in database. Particular map is used for web coevals that is stored as dataflow on the clipboard. On this dataflow several webs following maps can be performed
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( way optimisation, scope determination, path happening ) or can be used by external package. As a consequence of that analysis a dataflow is produced on the clipboard. Original and attendant webs can be queried at the same time. The user can maintain or cancel ensuing informations flow on the clipboard or retrieved in database.
The process for happening optimum constellation of secondary system consists of two possible optimisation stairss:
optimisation of new country secondary system and
optimum connexion of the peculiar client ( s ) to bing secondary system.
Sing urbanistic programs, ecological and esthetic restraints every bit good as old burden growing analyses possible locations of substations are known in progress. These premises make planning of secondary system more simple because merely routing procedure must be applied for several locations of substations and fixed locations of clients.
The first measure of routing procedure Begins by linking client to the nearest routing corridor. After that process, the secondary system web is generated by web faculty. On this web `` any way analysis '' is applied and as consequences of analysis there are all possible connexions between substation and clients. These consequences are used as input for external, CADDiN faculty of optimisation of radial structured webs. During this procedure of optimisation the set of regulations is used to fulfill standard patterns employed by interior decorators. The optimized web is so saved on clipboard in dataflow and can be diagrammatically viewed. The cost for the secondary system is chiefly the capital investing cost consisting of overseas telegram laying cost and cost of overseas telegrams. For each location of substation optimisation procedure must be repeated. Solution with minimum investing costs and satisfactory proficient restraints is the best sing secondary web. All solutions that are technically satisfied must be taken into history during the primary web optimisation. It is necessary because the local optimum of secondary system does non connote the optimum of primary system, and planetary optimum of distribution web.
The optimum connexion of the peculiar client to bing secondary system must carry through following two proficient every bit good as economical restraints:
the shortest possible length of connexion due to voltage bead that may be permitted ;
modesty in burden capacity of substation due to client burden.
The new client must be connected to the nearest neighbour client fulfilling antecedently mentioned restraints. The few nearest clients are found in a buffer zone with new client as a centre of this zone. The shortest way between new client and possible connexion node is found in two stairss: both nodes are connected to the nearest routing corridor, and after that by GIS web map `` happen best way analysis '' shortest way between nodes is found.
Due to the burden features, requested handiness and quality of energy supply two chief constellations of secondary system are used in optimum planning There is a ring construction ( get downing and stoping node is the same HV/MV substation and routing nodes are MV/LV substations ) and a nexus construction ( get downing node is one HV/MV substation routing nodes are MV/LV substations and stoping node is other HV/MV substation ) . Sing the use of GIS engineering the optimisation process of these two web constellations is really similar. In optimisation procedure three different jobs are considered:
optimisation of the new primary system ;
reconfiguration of the bing primary system sing predefined construction, and
support of the bing primary system with defined construction by put ining extra capacity in demand nodes or including the new MV/LV substation in the web.
The first job is similar to the jobs in optimisation of secondary system. There must be known all possible connexions and distances between HV/LV substation ( beginning node ) and MV/LV substations
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( demand nodes ) every bit good as themselves. Therefore, all web nodes must be connected to the nearest routing corridor. By `` any way analysis '' and heuristic algorithms ( soon familial algorithms are tested ) initial solution or `` zero-iteration '' is generated. After that by the brotherhood of GIS web map `` happen best way analysis '' and other heuristic methods optimum solution is found.
The 2nd job is more complicated than the first 1 because bing connexions in web must be considered in optimisation process. Otherwise, same processs are used as in the first job. Example of this optimisation process can be shown in the Figure 3.
In the 3rd job, optimisation process is similar to the process of adding the new client to the 2nd system. Little differences are in a manner of linking new substation to the bing web. In
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the primary system, sing the restraint of dependability of supply of energy to the client, each MV/LV substation must hold a possibility to be supplied from two sides. Therefore, the nearest bing overseas telegram between two substations must be found for the connexion of the new station, or the nearest routing corridor by which the new station could be connected to the nearest substations that are found in a buffer zone around it. When a better type of connexion is found, solution is tested on several proficient restraints ( electromotive force bead, overseas telegram and path burden, investing costs, etc. ) .
Small country or spacial, prediction is the anticipation of both the sums and locations of future electric burden growing in a mode suited for distribution planning which truly means with geographic declaration adequate for be aftering a new distribution web or extensions to the bing 1. The process is based on spliting a public-service corporation service country into a figure of sufficiently `` little countries '' and projecting the hereafter burden in each 1. This is normally accomplished by spliting a public-service corporation service country into either a grid of uniformly sized rectangular `` cells '' , or into `` equipment oriented '' countries matching to feeder or substation countries ( H.L. Willis, 1983,1992 ) .
Methods for computerized little country burden prediction, sing their information demands and analysis methods, autumn into three classs:
multivariate ( multivariable )
Basically these methods analyze past and present burden growing to place tendencies, forms, or information about the procedure of burden growing that is so used to project future burden growing.
Swerving methods require minimum informations ( they work merely with historical burden informations, normally one-year extremum burden ) and computing machine resources, and are comparatively straightforward in usage. Because of their simpleness and by and large the lowest disbursals, they were the most widely used techniques in the yesteryear.
Multivariate methods require well more informations ( historical tonss, geographic and demographic informations on clients and use ) and much more extended computing machine resources, but in return they by and large provide more accurate prognosiss.
Simulation methods in add-on to historical tonss require extended and comprehensive informations that include land usage type, geographic and demographic informations on a little country footing, transit and other diverse factors that may impact burden growing. They besides require considerable computing machine resources and work-force. On the other manus they offer advantages in truth and analysis of burden growing under altering conditions. Because of their complexness and demands simulation theoretical accounts have been beyond the range of many electric public-service corporations.
So far one can see that the nature of little country prediction requires heavy usage of computerized analyses and use of big measure of informations.
With its possibilities GIS is an first-class mean for developing and using simulation prognosis theoretical accounts. Of class, there is no restriction to utilize GIS for swerving methods, at least for some really fast qualitative reappraisal, or for short scope ( less than five old ages in front ) anticipations.
A service zone of a substation may be defined as a complex characteristic which comprises packages, edifices on those packages, electrical connexions for every edifice or client, bing interconnectednesss between clients hookups and associated substation etc. Packages, edifices and streets are modeled as polygons, and cadastral batch codification is attached to them as one of the properties. Statistical and census territories based on about equal figure of dwellers and cadastral territories are polygons, excessively. Second really of import information is address, modeled as complex characteristic category consisting a street name and figure. Polygonal analysis and polygon processing, which is possible in GIS, and address as a common nexus enables the contriver to find a substation service zone and cipher its country. Via characteristics ' properties all necessary clients ' informations ( one-year electricity ingestion, one-year extremum tonss, type of clients, some particular petitions and interfering factors, etc. ) are gettable. In that manner it is possible to track sums and kind of energy used by single client, or substation service country or some other part. Upon these information burden densenesss ( kWh/mA? ) or kWh gross revenues per client can be computed.
Procedure with constitutional constellating algorithm detects groups ( categories, bunchs ) of clients with similar yesteryear energy ingestion behaviour. For distribution burden calculating K-means algorithm [ Hartigan, 1986 ] is
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recommended, with a lower limit of 6-year burden history [ H.L. Willis, 1983 ] . The K-means algorithm hunts for a divider, that is, a set of bunchs that minimizes the `` entire difference '' between little countries and their assigned bunchs ( the mistake of the divider ) . It works by traveling little countries from one bunch to another. The hunt ends when no such motions of little countries cut down the mistake value.
This paper presents the construct of the pilot undertaking CADDiN for optimisation of electric distribution webs based on GIS engineering. The architecture of CADDiN consists of the heuristic methods implemented within GIS and procedural plans. In such a intercrossed environment, the GIS chief undertaking is to pattern `` existent universe '' , execute spacial analyses and guarantee the high truth of optimisation processs. The first consequences obtained by the paradigm database and developed processs promote that constructs and thoughts established in this paper can be applied on the existent jobs that exist in the distribution system planning.
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