Abstract: This paper introduces the design scheme of a SCADA monitoring system for a water supply project. The adopted SCADA monitoring system is a distributed control system based on industrial Ethernet, which has the characteristics of high decentralization, real-time performance, reliability, openness, and compatibility. Moreover, the redundant fiber optic transmission system can realize the synchronous transmission of data, voice, and video. The computer technology, control technology, network and communication technology, and display technology adopted in this design scheme reflect the latest development trend of water supply project automation systems. Keywords: Water supply project; SCADA system; distributed control; TCP/IP protocol 1 Overview The comprehensive automated monitoring system of the water supply project adopts a monitoring and data acquisition (SCADA) system based on computers and network information. The entire system uses industrial Ethernet as the main communication platform. The system will achieve the level of automation of monitoring, scheduling, and management of the entire network at the dispatch control center. Operators at the dispatch control center can complete the monitoring and operation management of pipelines through the SCADA system. Each station achieves a management level of unmanned operation with manned staff; the automatic control system will automatically and continuously monitor and control the pipeline operation, ensuring the safety of personnel, pipelines, and equipment; enabling the pipeline to operate normally with the lowest operating cost and optimal working conditions; the equipment, control systems, and materials used are technologically advanced, cost-effective, and mature products that meet the environmental and process conditions and have been proven in industrial applications; the communication between the station control system (SCS) and RTU of each process station and the dispatch center adopts a primary and backup communication channel, while also being compatible with GSM wireless communication channels; the dispatch control center communicates with the SCS of each station via optical fiber; the dispatch center and each station are linked point-to-point on the network. 2 System Network Structure The water supply system network structure is shown in Figure 1. To ensure the safe, stable, reliable, and efficient operation of the water supply system, advanced Siemens SCADA technology is used to monitor and control the process parameters and equipment operation of its water supply network and supporting facilities. Furthermore, the SCADA system is integrated with Management Information System (MIS) and Geographic Information System (GIS), which is an inevitable development trend. It is a crucial part of the entire water supply system. The urban water supply system's station control system uses RTUs to monitor and control the stations, transmitting key operating parameters from stations and pipelines to the dispatch control center via fiber optic communication channels, GSM networks, or wireless networks, adhering to the TCP/IP communication protocol and using SCADA system-specific data procedures. The system also receives operational instructions from the dispatch control center to remotely control critical equipment. To ensure the system provides detailed and reliable real-time information, promptly identifies potential problems, enables rapid command and dispatch responses to emergency repairs, and maintains uninterrupted business communication throughout the water supply system, absolute reliability of the communication system is essential. The design principles of the communication system are: Technological advancement: New systems require significant initial investment; therefore, the latest mature technologies from companies like Siemens must be fully utilized to avoid outdated technologies leading to repeated modifications and construction. This includes using fiber optic ring networks and standardizing the management and operation software for the monitoring center and various stations. Foresight in system construction: Urban water supply systems are complex information management systems; new needs, such as video monitoring and water usage information management, must be considered. New, existing, and future projects must be highly compatible and interconnected. Economic Practicality: While meeting voice and data service requirements, the overall construction and maintenance costs of the fiber optic communication network must be comprehensively considered, adopting the most economical and reliable integrated solution. System Resource Value-Addedness: System construction itself is a resource investment, necessitating consideration of resource value-added. Laying fiber optic cables becomes a new economic growth point in the form of resource investment. According to design requirements, a dual-redundant self-healing ring backbone network is selected, with "straight-line" or "small-ring network" access methods available to each node. For locations concentrated in one area or several points in close proximity, a "small-ring network" is recommended to improve reliability. Even if a communication failure occurs in a section of fiber optic cable, such as due to cable damage caused by pipeline maintenance, normal voice, video, and data communication will not be affected. The fiber optic cable is single-mode, suitable for SDH technology, equipped with 2.5Gb/s (STM16), transmitting 1550nm optical signals. Several standard E1 (G.703) interfaces are separated through optical transceivers to form a PABX network. Routers providing standard E1 interfaces are used to access the LAN (TCP/IPIO/IOOM) network. For unattended stations where voice communication is not required, fiber optic to Ethernet conversion devices can be used. 3. Control System Configuration The water supply project's SCADA system consists of a control and dispatch center, several station control systems, and dozens of pipeline monitoring units (RTUs). These range from a few hundred meters to several hundred kilometers. (See Figure 2). Under normal circumstances, the dispatch and control center centrally monitors the entire network, and can also remotely control particularly important individual devices. Operators at the dispatch and control center monitor, operate, and manage the entire network through a computer system. Each station's control system or RTU completes its respective control tasks under the unified command of the dispatch and control center. Control authority is determined by the dispatch and control center; only after authorization from the dispatch and control center are operators allowed to perform technical tasks within the authorized scope at each station through the station control system or RTU. When the data communication system fails or the system is under maintenance, the station control system or RTU should independently monitor and control its own station. Local manual control can be used during equipment maintenance or emergency shutdowns. Under both normal and abnormal conditions, the SCADA system automatically monitors, protects, and manages the water pipeline. The two servers in the backup dispatch center and control center work together as backups to continuously monitor each station control system and pipeline monitoring point. Each station control system and RTU, as the remote control unit of the SCADA system, is the foundation for its normal operation. They are the remote execution units for the dispatch control center's dispatching, management, and control commands, representing the most basic monitoring level in the SCADA system. The SCS and RTU can independently acquire and control data at their respective process stations, transmit relevant information to the dispatch control center, and receive commands. The station control system (SCS) mainly consists of a computer network system, a programmable logic controller (PLC), operator workstations, and communication equipment for data transmission. The RTU is an independent, small, intelligent control device with flexible programming configuration, comprehensive functions, strong communication capabilities, convenient maintenance, strong self-diagnostic capabilities, adaptability to harsh environmental conditions, and high reliability. Each station's station control system (SCS) or RTU will perform tasks such as monitoring and interlocking protection for its respective station, and will receive and execute commands issued by the dispatch control center. The integrated automation system implements the following operating modes: ● Centralized monitoring and control of the entire system by the dispatch control center; ● Automatic/manual control of the station control systems; ● Automatic/manual control of individual station equipment (such as compressor units) and station subsystems. To ensure the real-time nature of data exchange between stations in the SCADA system, and to ensure its timely, accurate, reliable, coordinated, and efficient operation, the SCADA system's data updates should employ multiple methods, such as periodic scanning, exception scanning, querying, exception reporting, and alarms. The dispatch control center's real-time server communicates with each station control system (SCS) point-to-point, operating online via a network. Under normal circumstances, the system uses periodic scanning, i.e., regularly updating data at fixed intervals. Each point in the SCADA database has a defined scanning cycle based on its characteristics. The data update time for a full-line scan of the SCADA system network does not exceed 15 seconds. When a sudden event or special request occurs in the system (such as issuing an operation command, focusing on monitoring a specific area, or triggering an alarm), the system will interrupt periodic scanning and use other scanning methods to prioritize the transmission of important data and commands, ensuring system real-time performance. 3.1 Dispatch and Control Center (See Figure 3) The SCADA computer system of the dispatch and control center adopts dual-network redundancy and a distributed architecture. The SCADA computer system consists of a SCADA real-time data server, a SCADA historical data server, a SCADA WEB server, an analysis server, a print and application server, operator workstations, engineer workstations, pipeline simulation workstations, a background system, a projector, redundant disk arrays, tape drives, printers, switches, network communication equipment, and GPS clock equipment. To improve system reliability, the SCADA real-time data server, the SCADA historical data server, and the local area network adopt a hot standby redundancy configuration. The dispatch and control center communicates with various station control systems and pipeline monitoring point RTUs through a backbone fiber optic ring network. Utilizing Siemens SIMATICNET technology, an open industrial Ethernet network is constructed, compliant with TEEE 802.3U standards. This network allows for device interaction and fault diagnosis from any point within the network and features a redundant network topology. Network components are EMC tested, exhibiting strong anti-interference capabilities and suitability for harsh industrial environments. Communication with any station control system's PLC can be achieved via Ethernet cards, and the system adheres to the TCP/IP communication protocol. Ethernet switches on the network are key devices for realizing the monitoring functions of the SCADA system. Notably, Siemens' OSM fiber optic switch modules and ESM electrical switch modules offer low cost and high efficiency. Using Siemens SCALANCE series switches to establish a 10/100 Mbit/s industrial Ethernet network facilitates network topology construction and provides powerful, high-quality network management and diagnostic services, offering customers an ideal network solution. 3.2 Station Control System The station control system is the control system for the pumping station, including PS1, PS2, and PS3. This system mainly consists of a remote terminal unit (RTU/PLC), a station control computer, communication facilities, and corresponding external equipment. The station control system uses the RTU/PLC to monitor and control the station, and configures, analyzes, and processes key operating parameters of the station and pipelines using the unique data configuration of the SCADA system (Figure 5). Operators can understand the working status of the pumping station and control the operation of the pipeline network through SCADA software. An open industrial Ethernet network is used, conforming to IEEE 802.3U, allowing equipment startup and fault checking from any point in the network, and featuring a redundant network topology. The server can achieve real-time communication connection with the PLC by configuring an Ethernet card, and the system follows the TCP/IP communication protocol. 3.3 Pipeline Monitoring Points The pipeline monitoring points for this project include: the pressure stabilization device—PI station, the booster station, and dozens of distribution stations in cities along the pipeline route. Data is transmitted to the dispatch control center via fiber optic channel, and the system receives operation instructions from the dispatch control center to complete remote control of key equipment. The station control system has the ability to operate independently. When a component of the SCADA system fails or communication between the station control system and the dispatch control center is interrupted, its data acquisition and control functions are not affected. The station control system structure diagram is shown in Figure 4, utilizing an industrial Ethernet network. The pump station's SCADA computer system adopts a single-machine redundant, distributed structure, consisting of SCADA workstations, printers, switches, and network communication equipment. The SCADA workstations acquire data from the pump station's PLCs in real time. Communication between the PLCs at these monitoring points and the workstation computers is achieved via a local area network, using the standard TCP/IP protocol to enable resource sharing between the PLCs and computing devices. See Figure 5. These monitoring stations are typically distributed along urban network pipelines, in the field, and unattended. Depending on the actual environment, outdoor PLCs may be used if necessary, suitable for harsh environments. The PLC design adopts a centralized principle, with the PLC acquiring or controlling corresponding signal quantities through I/O ports. It connects to the backbone fiber optic network via an Ethernet communication module and an Ethernet-to-fiber optic interface device. For ease of operation, a portable PC can also be used to operate the PLC. 4. Conclusion This article only introduces how Siemens automation technology was used to build an open monitoring system for the industrial Ethernet portion of a water supply project's SCADA control system design, providing a reference for the design of similar project automation systems. With the continuous development of industrial control and IT technologies, advanced automation control concepts and technologies are increasingly popular in the water industry. Distributed monitoring systems based on industrial Ethernet networks have become the mainstream of water industry automation. Through standard open TCP/IP protocols and 100Mbps Fast Ethernet (and potentially 1000Mbps or higher), various control devices and different networks can be seamlessly connected, achieving high-speed data transmission and real-time control. This is safe, reliable, and economical for the water industry. Click to download: SCADA Monitoring System for Water Supply Projects Based on Industrial Ethernet Editor: Chen Dong