With the development of power system automation and enterprise management modernization, various power supply enterprises have implemented application systems such as SCADA/EMS, DMS, MIS, and GIS through computer and network technologies. These systems are managed by different departments, developed by different manufacturers, and implemented separately. This makes the maintenance and management of the entire automation system extremely inconvenient. Therefore, a network support platform that can coordinate these various application systems is proposed, enabling it to both meet the needs of phased implementation of various functions and achieve unified management and meet the application needs of various functional departments within the enterprise. [b]1 System Topology[/b] The network structure is based on the Internet and Web model. Each application system can be easily connected to the network and operate relatively independently. Under the management of the support platform, clients on the network can access data from various application systems on the support platform, and this data can be shared and reorganized. The PAN Desk (power automation network desk) adopts a Client/Server structure. The entire system is mainly divided into the following four parts (as shown in Figure 1). [img=310,126]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dlxtzdh/dlxtzdh99/dlxtzdh9901/image/45.gif[/img] Fig.1 Topology structure of PAN Desk a. Front-end unit: Includes communication with RTU and system GPS synchronization clock processing. If a SCADA system already exists, a front-end unit is not required. b. Servers: Includes 2 main servers (or host) PAN Desk servers, 1 web server, and multiple other application system servers. c. Clients: Includes 2 dispatchers (expandable to multiple) and multiple browsers on the network. The PAN Desk browser program on the dispatcher is the only client that can perform remote control operations. In addition, the dispatcher can support multi-screen display and also provides an interface for large-screen display. d. Network: To meet multimedia applications, a 1000 Mbit/s Fast Ethernet is used. **2 System Software Design** 2.1 System Software The PAN Desk server uses Microsoft Windows NT Server 4.0 (Chinese version), supporting at least 20 clients; the scheduling machine uses Microsoft Windows 98 (Chinese version); the browser can use Windows NT 4.0 or Windows 95 Chinese version; the database management system (DBMS) uses Microsoft SQL Server 6.5; the web server uses Microsoft Internet Information Server 4.0; the web browser uses Netscape Communicator 4.0 (Chinese version) or Microsoft Internet Explorer 4.0 (Chinese version). 2.2 PAN Desk Application Software Structure The application software in the PAN Desk system mainly includes the following three parts, and their interrelationship is shown in Figure 2. a. PAN Desk Server Program: Runs on the PAN Desk server, mainly responsible for real-time data acquisition and processing, database management, and data interaction with clients; b. PAN Desk Client Program: Runs on the PAN Desk client, mainly responsible for the human-computer interface, page editing, and database display; c. Web Application: Runs in the web browser, providing web platform support. 2.3 PAN Desk Server Program 2.3.1 Data Acquisition Program The data acquisition program receives raw data sent from the RTU, performs necessary preprocessing (such as protocol conversion), and then transmits it to the data server program for processing. For existing SCADA systems, it directly accesses the SCADA system database. 2.3.2 Data Server Program Responsible for data management: a. Creates, stores, retrieves, and modifies the database using standard SQL statements. b. Database backup: Synchronously copies the stored data from the primary server to the backup server, always maintaining a complete backup of the data. c. Implements a real-time database for fast access using a dedicated algorithm, maintaining an internal interface with the SQL database. For users, the use of this real-time database is consistent with that of the SQL database. d. Provides security protection for the database, allowing only authorized users to access specific data. e. Event handling: Responsible for judging, identifying, and storing all events (including alarm events) within the system, and displaying them to the client through the SCADA system interface module. 2.3.3 Data Definition Editor (VDT) Responsible for defining the relevant data characteristics of the system, plant, and RTU data points. When a user edits or modifies the VDT, the VDT image stored on each endpoint of the network is automatically refreshed. 2.4 PAN Desk Client Program 2.4.1 Client MMI Program The client MMI is the application running on all PAN Desk clients. This program provides users with the SCADA display interface and operation interface. a. PAN Desk uses a "page" approach to organize various screens, and users can access pages through page navigation bars, etc. b. PAN Desk pages are divided into user pages and system pages. c. For authorized users, data can be manually entered through the page; each operation and the operator's name will be automatically recorded in the event log database for future reference. d. MMI also provides a dedicated display area showing the current time and current network status. 2.4.2 Multi-Screen Support Multi-screen display (generally dual-screen display) provides users with a convenient way to view more information simultaneously. 2.4.3 Page Editor The PAN Desk page editor is used to edit and create user pages, featuring object-oriented design, rich editing functions, and direct embedding of data objects into the page. 2.5 Web Application The PAN Desk system is an open support platform. One of its most significant open features is the integration of Web technology into the system architecture. The Web server and browser constitute a Web-based Client/Server model. This model resides within the same system as the conventional PAN Desk client/server model, operating independently yet interactively. The Web application includes all relevant code within the PAN Desk system that supports the Web platform. Unlike traditional applications, Web applications cannot run independently of the Web server and Web browser. Their code is either stored in the relevant directory of the Web server or as a plugin for the Web browser. 2.5.1 Web Application Functions a. Existing AutoCAD drawings can be directly viewed in the Web browser, and operations such as browsing, overall zooming, partial zooming, and printing can be performed on the drawings; b. Video system image files can be viewed and audio files from the telephone recording system can be played in the Web browser; c. SCADA data can be viewed in the Web browser; d. The Web browser can serve as the user interface for viewing the MIS (Management Information System). 2.5.2 Web Application Components a. Browser Plugin: Provides support for AutoCAD files and multimedia; b. Server-side CGI (Common Gateway Interface): Provides access to SCADA dynamic and historical data; c. Java Application (applet): Provides display of SCADA dynamic data. 2.6 Application System Interface Software PAN Desk is a widely adaptable open platform on which various application systems can be easily integrated, allowing users to use each system with a consistent or similar interface. Each application system maintains only its unique server program and does not require a dedicated user interface. The interface design of several major application systems is introduced below. 2.6.1 SCADA System Interface The SCADA system is the foundation and core of power grid dispatch automation. Therefore, the interface with the SCADA system must consider the requirements of openness to ensure a certain degree of universality, and also consider the requirements of real-time performance to meet the actual needs of power grid dispatch. PAN Desk interfaces with SCADA in the following ways: a. It identifies each data point (RTU data) using a data identifier (ID) method, and data access is performed through the ID; b. It establishes a resident memory real-time database on the server side, while maintaining a mirror database on the client side; c. The server and client sides maintain a hot connection, and only the data requested by the client is transmitted to the client's mirror database according to the client's request; d. The server and client sides use a TCP/IP-based application layer protocol (PDP protocol); e. PAN Desk provides a set of SQL-based database access interface functions (APIs) for other application systems to access SCADA data. 2.6.2 Interface with Distribution Network Automation System The distribution network automation system interfaces with PAN Desk in the following ways: a. The distribution network automation system accesses the SCADA database using the API functions provided by PAN Desk. b. The SCADA system is SQL-based; therefore, if the distribution network automation system also uses an SQL database, the SCADA system can access it in SQL mode. If the distribution network automation system uses a custom database, the supplier needs to provide interface functions. c. The distribution network automation system uses the PAN Desk page format. d. If the distribution network automation system contains a custom screen display format, the file format must be provided. PAN Desk can unify the display method using one of the following two methods: convert the custom format into a PAN Desk page for display in the PAN Desk client MMI program; or write a web browser plugin for display in a standard browser. e. PAN Desk treats the distribution network automation system as a subsystem, assigns it a data ID, provides data buffering from the main server, and follows the PDP protocol with the client. 2.6.3 Energy Billing System Interface The interface between the energy billing system and PAN Desk only involves PAN Desk accessing its database. Therefore, as long as the energy billing system uses an SQL database, the PAN Desk server can access it via SQL. The energy billing system, as a subsystem of PAN Desk, is assigned a data ID within a specified range and communicates with the client according to the PDP protocol. 2.6.4 Video System Interface a. Decodes and converts image files sent from the field video monitoring system, supporting file formats such as BMP, MPEG, and JPEG. b. Supports downlink audio channels. c. Uses a multimedia server to store video images; users can define the image data retention time. d. Install a plugin on a web browser so users can view video images. 2.6.5 Network Telephone Recording System Interface a. The PAN Desk system accesses the recording system's data files via file sharing. b. Playback and retrieval of recorded files are performed via a web browser. 2.6.6 Interface with the MIS System Install the MIS system's browsing program on each client machine. [b]3 Conclusion[/b] This open support platform can integrate different application systems onto a network, allowing users to easily add application systems as needed. For example, the dispatch console no longer needs to add a computer for each new application system. When the distribution network and its substations belong to different power supply bureaus, the technical difficulties of system reconfiguration of the distribution network automation system can be easily solved through this support platform and a wide area network or the Internet.