Application of Siemens Industrial PC and WinCC Industrial Control Software in Wastewater Treatment Plant Monitoring System

　　Application of Siemens Industrial PC and WinCC Industrial Control Software in Sewage Treatment Plant Monitoring System

　　1. System Overview

　　The sewage treatment plant monitoring system is an upgrade based on the original control system. It consists of two TI PLCs, Profibus fieldbus, Siemens industrial PC, WinCC industrial control software, 100 Mbps fast Ethernet, and 10 client PCs. It realizes and improves centralized monitoring and control functions of various control equipment from the inlet screen to sludge thickening, and adds some new control functions on the original basis.

　　The system collects field signals from pumps, valves, and other equipment directly into the PLC, which completes manual and automatic program operation and local and remote control of the equipment. Siemens Profibus communication templates are installed on the PLC, connecting to the WinCC monitoring industrial PC in the control room via Profibus bus and FMS protocol. Profibus bus is currently the fastest fieldbus in the world, with a maximum speed of 12 Mbit/s. Control status and data of field equipment are sent through the Profibus network to Siemens WinCC industrial control software for display, storage, alarm, and report printing management functions. Operators in the control room can understand equipment operation status, energy consumption statistics, and sewage treatment conditions through operator terminals, issue dispatch commands, and directly control field equipment. The WinCC industrial PC and office computers are connected via 100 Mbps fast Ethernet, forming a small enterprise internal LAN. Office management personnel use standard network browser IE5.0 on office computers to connect to WinCC software and monitor the entire plant operation and control field equipment according to permissions. Live video images from field cameras are integrated into the control room WinCC monitoring system and transmitted to office management computers using network transmission technology for live video images.

　　2. System Structure

　　3. Control Modes

　　1. Remote Control

　　---- When the mode selector switch on the control cabinet is switched to remote control, operators can choose automatic or manual control modes. In automatic mode, the PLC controls equipment start and stop according to various interlock and linkage logic relationships. Control room operators can issue dispatch control commands based on field conditions to adjust equipment operation status to meet process requirements. Operators can also select remote manual mode to directly manually control individual field equipment.

　　2. Local Control

　　---- Local control has a higher priority than remote control. When the mode selector switch on the control cabinet is switched to local automatic control, dispatch control commands from the control center are blocked, and equipment runs automatically under PLC control. In local manual mode, field operators start and stop equipment via manual buttons on the control cabinet, which provides basic control interlocks.

　　4. System Functions

　　1. Display Function

　　---- The monitoring system vividly displays the process flow, equipment status, plant overview, and process layout diagrams using graphics or images. It monitors liquid level, flow, and other points through I/O input/output fields, bar charts, curves, and data tables. Video camera images are integrated into the monitoring screen as a whole. Monitoring screens can be browsed on client machines via standard IE browsers, reducing engineering costs. The system also provides operation prompts and automatic blocking of misoperations. Screen switching speed is less than 3 seconds.

　　2. Alarm Function

　　---- The system automatically performs alarm and event handling. When an alarm occurs, such as high liquid level or fan overheating, the system quickly detects it, prompts via screen status changes, displays and prints corresponding alarm texts, and issues sound alarms to alert monitoring personnel. Alarm arrival time, confirmation time, clearance time, alarm value, limit value, current operator, and other relevant information are automatically archived. Two types of sound prompts are used for alarm arrival and un-cleared alarm confirmation. Alarms can be manually muted. Alarm information is stored for six months for fault analysis and inquiry. Operation events and status changes are also automatically stored and archived.

　　3. Data Archiving

　　--- Values such as flow, sewage treatment volume, and power consumption are automatically stored at defined intervals. Stored data can be displayed as curves or data lists. Functions include historical data query, zoom display, observation lines, online curve toggling, online time range adjustment, and online display mode adjustment. Stored data is kept for 13 months.

　　4. Report Function

　　--- Report printing can be automatically performed at defined times or manually triggered by button. Accident alarms can be printed anytime, and the latest 1000 records or 30 days of archives can be output as needed. Monthly report data is automatically accumulated and printed on monthly reports. Report files are automatically saved on the hard disk during printing for re-output. Stored reports can be opened and viewed within the system.

　　5. User Management

　　--- Operators must log in to operate equipment. The system automatically restricts operations based on the operator's level. When an alarm occurs, the current operator is recorded and archived. When client users browse with IE, the system displays and controls screens and operations based on username and password. Unauthorized users can only browse screens and cannot modify parameters or control equipment.

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