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Support System for Gas Distribution Network
GIS group, Faculty of Geodesy and Geomatics
K.N. Toosi University of Technology,Tehran,Iran.
The main parameters in evaluating a gas distribution network design include:
- Reliability of resulted network in providing proper gas pressure
- Cost of implementing the network
- Management capability and flexibility of the network in the occurrence of crises/events On the other hand, the following problems regarding the design of the distribution networks should be considered:
- Most of the maps and procedures are done in a CAD-Based system. Although they are powerful in visualization, they unconvincing in analysis
- Incoherence and separation of stages and processes of the design done by different people
- Lack of a proper data management
Data and maps generated during network design
A large portion of the information used by gas distribution companies is gathered and created during the distribution network design. The data is created and stored in the form of DWG files,Tables and Reports. These include the map data of blocks of the city, node-map, designed network, land ownership, feeding network, etc., and the tabular data consists of the results of the market analysis, results of the network hydraulic calculations, list of the material used in the network, and the customers information etc. (A’inechi, 1993).
Units involved in the design of the gas distribution network
Different processes and stages of the network design are done by many engineering units. This includes market analysis unit, the network control unit, the design unit, cathodic protection unit, surveying unit, implementation unit, customer service unit, and emergency unit. Also there are different duties and responsibilities, a need for diverse map and other datasets needs.
General goals of using GIS in the network distribution design
The customers of the gas are distributed in space and the design should follow the spatial pattern of these customers. In other words, the design of the distribution network is a spatial design and spatial decision problem. Therefore, GIS as the most powerful and commonly used spatial analysis tool, can be used to improve different aspects of the distribution network design.
As mentioned by Boulos (2004), introducing and using of GIS in different stages of the network design will bring about many benefits. This includes the reducing of data redundancy and improving of data sharing among different units and processes, better data management, providing of data query and analysis tools, providing of visualization tools for representation of data and analysis results, improvement of system and optimization of processes, providing of the development tools for improvements regarding data editing and data quality control.
Design and implementation of a Geodatabase for the design and extension of the gas distribution network
The Geodatabase model is an object oriented data model. In this model, intelligent objects are created that simulate the natural attributes and behaviors of the real-world features. It also models the relationships between the real-world features (Zeiler, 1999).
Among the benefits of using a Geodatabase model, the more important ones are: the ease of creation, editing and analysis of geometric networks, the ease of editing data with topological relations, the controlled data entering with easily defined regulations and rules, protection of the consistency of the database, and finally the ease of developing application programs for accessing data in Geodatabase using SQL sentences and user-friendly interfaces. Some of the rules that can be implemented in a Geodatabase are:
- Geometric network rules
- Spatial relationship rules
- General relationship rules
- Attribute rules
Geodatabase comprises the central part of the GIS. All processes related to spatial and non-spatial data management, quality control and data integration are done by Geodatabase (Marv 2002). Using the Geodatabase capabilities, Geometric Network, and UML, the conceptual model of the spatial database required for the gas distribution network was created. ArcGIS software was selected as the basic software environment for the implementation of the system. The designed conceptual model was implemented using the available tools of ArcCatalog. The result of this procedure was the creation of a Geodatabase with a set of empty layers along with empty data fields and defined relations. Figure 1 shows the layers of the implemented Geodatabase. Some of required processes are implemented using the existing tools and functions available in ArcGIS. For many other required processes, suitable tools and functions are developed and added to the GIS using the programming environments of VBA and ArcObjects.
Fig. 1 The module developed for the design and extension of the gas distribution network
Design and extension of gas distribution network
The designed and developed GIS provides a proper framework for the management of the data and execution of all design processes. For the design of a city’s gas distribution network, we only need to enter and fill in the defined data layers and tables and start the sequence of the processes as defined in the system.
The main difference between such an extended system and a usual multi-purpose GIS is that, all tables and layers of the database are empty and during the design procedure, the generated data are entered to the proper layers and tables, according to the specified standards and rules. In addition, some parameters of the quality and correctness of the data are controlled by the system. The implementation of the required and developed functions are grouped in a new module called GGIS, which is added to the user interface of ArcMap and can be used easily by the units involved in the design procedure. This module and its developed functions are represented in Figure 1. The developed system is tested and evaluated using the dataset of a region of Tehran city called Khoshnam.
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