Changzhou City has been in Existence in China for More Than 2500 Years. The city is situated on the Grand Canal, an important transportation and trade route that was first constructed in the fifth century B.C. and has been extended several times since. Changzhou City has enjoyed periods of rapid and thriving expansion, and today it is one of the major industrial towns in Jiangsu province and is known for food production, textiles and machinery.

The Changzhou distribution network is being developed to satisfy the city's increasing demand. The resulting complex system now requires a geographical information system (GIS) to effectively manage the network. GIS offers geographic and space features in a system that can provide input, storage, edit, query and analysis functions, and become an information source for the decision makers of Changzhou Electric Power Supply Co. (CEPSC; Changzhou, Jiangsu, China). This technology, integrated with the GIS, provides managers information on the distribution network, energy markets and customer services.

As a result of continuous efforts, CEPSC has installed a GIS system based on an integrated information system and automatic mapping/facility management/GIS technology. By combining the system modes of client/server and browser/server graphics, the city distribution network — in terms of cables, lines and substations together with power user information — is now stored online. This comprehensive data system is updated and subject to continuous and dynamic review.

SYSTEM ARCHITECTURE

The power GIS system is based on the ArcInfo developed by ESRI (Redlands, California, U.S.) as a geographic information platform. For the spatial database, namely the spatial database engine (SDE) that stores the graphics data, CEPSC selected the IBM DB2. The server operating system is the Win2000 advanced server. To minimize the cost of the project, the MapObjects 2.0, which is the low-cost component from ESRI, was adopted for connection to the SDE spatial data stored in the server. The Delphi 5.0 software development tool also was installed.

The main server for the GIS system is an IBM ×360 connected to the application department through a 1000M fiber and 100M Ethernet network. The gigabit network provides the highway for the vast quantity of graphics and network data. Some 25 workstations in different departments within the company have direct access to the GIS. While the distribution operations and sales/marketing departments are responsible for data collection and updating, many other departments increase the number of users that have access to quickly and conveniently interrogate the system.

ESTABLISHING THE GIS

The features of the GIS system include:

• Investigation and augmentation of system demand data

• Transforming the format of the digital map

• Forming and adjusting the model of distribution system

• Software development and debugging

• System testing and trial operation.

Data modeling is key in establishing the GIS system because the distribution network is complex and ever changing. The power-delivery system includes substations, overhead lines and underground cables, which encompass a variety of components including poles, transformers and switches. Each of these components can be catalogued in geographical, topology and electrical formats, and the GIS model must reflect the component's geographic position, relating them to the topographic and electric features.

In the GIS system, different types of lines, transformers and switches represent overhead lines and cables, and are indicated by point symbols that form the abstract structure of the distribution network. The 400-V circuits and users form the branches of the GIS system, and the 110-kV substations, 10-kV overhead lines and cables, and distribution substations constitute the trunk of the supply network.

GIS SYSTEM APPLICATION

The CEPSC supply network extends more than 700 sq km (270 sq miles) via a network comprising 2200 km (1367 miles) of overhead line and 167 km (104 miles) of underground cable. The system peak demand of 3500 MW is increasing by some 16% annually. The GIS system was installed in the 10-kV distribution substations on the Changzhou City distribution network. The database was developed by inputting the data for some 300 distribution lines, 2000 distribution substations, 3000 distribution transformers, and 3400 high-voltage and 290,000 low-voltage customers. The staff from CEPSC and the Nanjing Ziwu Information Technology Co. (Nanjing, Jiangsu), which was selected in 1999 to be the system development partner, completed this challenging task in almost two years.

Main system functions include:

• The distribution lines and cables can be presented graphically with the use of color to differentiate between lines and cables, and their operating voltages

• The distribution network can be stored and edited on the GIS system, and system users can manage the diagrammatic geographic information

• All components of the distribution network can be input, modified and queried

• Specific and statistic information on all customers supplied from the distribution network can be identified and located conveniently at high speed

• All component fault and circuit patrol records can be integrated into the GIS system, providing network managers all the data for decision making

• The GIS power-system analysis feature enables the simulation of all network operation

• The system establishes an interface with other information systems, such as energy sales, marketing information, load control and SCADA systems. Different systems sharing a common database can ensure the integrity and exclusivity of the data source.

VALUE DELIVERED

As the computer manages the distribution network, many users can share it. This reduces workload and staff time, avoiding work duplication. The system has significantly improved network efficiency and facility management. Integration of the fault and defect records has improved the organization and efficiency of the staff working on these activities.

The combination of network and consumer data enables the utility to respond to requests for new supplies and increased demand with minimal delay. Power company staff benefit from the distribution network design facilities that also provide minimum circuit loss solutions as a feature of the network analysis functions.

The distribution network GIS gives the utility the opportunity to operate the existing network efficiently; and in seeking optimum performance, the quality of network management has improved significantly. As a result of the quality data now available on system faults and defects, system-outage times have been reduced, improving the level of customer service.

Since the implementation of the GIS, CEPSC has recognized and now appreciates the value of investing in advanced information technology. This has prompted the need to continue to conduct research to maintain and improve the level of power-system management and customer service.

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Qiang Xu is an engineer currently working for the Changzhou Electric Power Supply Co. in Jiangsu, China, with a focus on information technology applications. xuq1@jsepc.com.cn