[b]I. Introduction[/b] In recent years, with the rapid development of my country's economic construction, many regions have experienced a shortage of power resources, leading to the construction or expansion of many power plants. Shenzhen Western Power Plant originally had four 300MW units (#1-#4). To increase power generation capacity, units #5 and #6 (2×300MW) were added. The plant originally had two chemical water treatment systems. The expansion project added a 100-140m³/h chemical desalination system, with the remaining equipment shared with the existing systems. The original chemical water treatment system used a traditional analog panel monitoring method, resulting in low automation and efficiency. After the addition of the two units, the original chemical water treatment system's control system was abolished, and both the original and the expanded system were centrally controlled using a single redundant PLC control system. **II. Chemical Water Treatment System Process Flow** 1. The original chemical water treatment system process was: Tap water → Storage tank → Booster pump → Activated carbon filter → Cation exchanger → Carbon dioxide remover → Intermediate water tank → Intermediate water pump → Anion exchanger → Mixed ion exchanger → Demineralized water tank → Demineralized water pump. Through on-site investigation of the existing system's operation and analysis of water quality reports, it was found that the suspended solids content in the tap water was high, severely polluting the activated carbon and ion exchange resin. Therefore, the continued construction project will add 3 high-efficiency fiber filters to deeply filter the tap water. The continued chemical water treatment system process is: Tap water → Storage tank → Booster pump → High-efficiency fiber filter → Activated carbon filter → Cation exchanger → Carbon dioxide remover → Intermediate water tank → Intermediate water pump → Anion exchanger → Mixed ion exchanger → Demineralized water tank → Demineralized water pump. 2. Connection and Operation Mode of the Continued Construction Project with the Existing System: The existing system has two 120t/h capacity primary desalination + mixed bed units. The continued construction project will only add one more 120t/h unit of the same equipment. The demineralized water pump, reclaimed water pump, compressed air system, acid-base regeneration system, and wastewater treatment system are shared with the existing system. Three high-efficiency filters operate in parallel, with two operating and one on standby under normal conditions. The high-efficiency filters pre-treat not only the tap water required for the continued construction project but also the tap water from the existing system. Two activated carbon filters and the primary desalination unit form a series, operating in series, with two units operating and one on standby under normal conditions. Within each series, one of the two activated carbon filters operates (removing free residual chlorine) and one is on standby when the water quality is good; both operate simultaneously (removing organic matter) when the influent water quality deteriorates. The mixed bed unit operates in parallel, with two units operating and one on standby under normal conditions. Switching valves are installed between the three primary desalination units and the three mixed beds. Due to limitations of the existing system, only the #1 primary desalination unit and #1 mixed bed can operate simultaneously with the #2 primary desalination unit and #2 mixed bed, and the #1 primary desalination unit and #1 mixed bed can operate simultaneously with the #3 primary desalination unit and #3 mixed bed. When the unit starts up, all three sets of equipment operate simultaneously to meet the maximum makeup water volume. [b]III. System Configuration[/b] The system consists of two host computers and a redundant PLC system. The host computer system uses an industrial-grade computer to form a powerful monitoring and control system. The computer is equipped with Intellution's FIX 7.0 industrial monitoring and control system software. Through reasonable system design and configuration, dynamic monitoring and control of the entire chemical water treatment process are achieved. Through the host computer system and a powerful industrial control transmission network, automated management and control of the entire production process are realized. The PLC selected is the Dvison PPC11 redundant controller. The control system adopts a dual-machine hot standby redundancy method, connecting to the points requiring monitoring and control in the field via remote I/O. The remote I/O consists of a communication processor and PPC11 series I/O modules. The redundant main control station ensures zero system downtime for maintenance, minimizing human intervention. A high-performance industrial Ethernet bus transmission network is used between the main control system hot standby system and the remote I/O control station to achieve reliable, secure, and stable information transmission. An industrial Ethernet transmission network is also used between the host computer system and the PLC control unit. Ethernet is an international standard, and industrial Ethernet has achieved high transmission security and reliability requirements. It is now widely used for program maintenance, transmitting factory data to MIS and MES systems, monitoring, connecting human-machine interfaces, and recording events and alarms. Industrial Ethernet has advantages such as high transmission speed (currently reaching 100M), deterministic hub technology, no need to consider network topology, diverse transmission physical media (twisted pair, fiber optic, coaxial cable), and hub applications without considering network expansion. The upper-level computer system and field monitoring and control points are tightly integrated into a whole through an Ethernet network, forming a complete system. On such a high-speed transmission network, the unique functions of the PLC system can be easily utilized to achieve online remote diagnostics of the entire control system. [b]IV. Control Functions[/b] All control valves in the water treatment system adopt local and remote control methods. Even in the event of a complete failure of the programmable control system, manual water production can still be achieved through local control, ensuring reliable water supply for the unit's boiler. A 3-position selector switch is used on the control box, namely local open, local close, and remote control. When remote control is selected, the control valve is controlled by the operator at the operator station. The operator can monitor the status and control the operation of the control valves at the operator station, and the control valves can be selected in automatic or manual mode. In automatic mode, the control valve is controlled by the PLC logic program; in manual mode, the control valve is directly controlled by the operator on the operating interface. The commissioning and regeneration of the primary desalination equipment are automatically controlled by the PLC, and can also be remotely operated via keyboard and mouse at the operator station in the control room. When the conductivity of the effluent from the primary desalination unit exceeds the specified value or the cycle water production reaches the specified value, the system automatically disconnects and alarms, then automatically initiates the regeneration program. The operation and regeneration of the mixed ion exchanger are automatically controlled by a PLC, or remotely operated via keyboard and mouse. When the conductivity and silica of the effluent from the mixed ion exchanger exceed the specified values, or the cycle water production reaches the specified value, the system automatically disconnects and alarms, then automatically initiates the regeneration program. The HEPA filter and activated carbon filter are automatically controlled by a PLC, or remotely operated via a keyboard and mouse on the control room's operating station. When the inlet and outlet pressure difference exceeds the specified value, or the cycle water production reaches the specified value, the system automatically disconnects and alarms, then automatically initiates the backwash program. Previously, all of these operations were performed by operators; after implementing the new system, these operations can be performed without operator intervention. The water level in the intermediate water tank is automatically controlled by a PLC (by adjusting the cation exchange bed inlet regulating valve), ensuring that the water level in the intermediate water tank remains stable at the normal position when the primary desalination system is in operation. The intermediate water pump's start/stop is interlocked with the intermediate water level, ensuring safe operation by starting the pump at low levels and stopping it at high levels. The control status of valves and pumps is displayed, allowing for automatic/manual/local operation and interlock selection. All system flow and pressure data can be monitored in real-time on the operating interface. Raw water flow, anion bed outlet flow, and mixed bed outlet flow are displayed, accumulated, and historically recorded. The water production capacity of primary desalination and mixed bed regeneration can be viewed separately. The system controls the commissioning, shutdown, and regeneration procedures for each desalination unit, as well as automatic acid and alkali addition procedures and automatic/semi-automatic startup procedures for another desalination unit. For sequential control settings, necessary step-by-step, group, or individual operations are provided, along with skip, interrupt, or bypass functions. System commissioning, activated carbon cleaning, primary desalination regeneration, and mixed bed regeneration can be completed automatically by the system or manually by the operator using step-by-step increments. The operating station interface displays the set time and remaining time for each step, as well as step and delay indicators. V. Conclusion The chemical water treatment system of Shenzhen Western Power Plant was officially put into operation in July 2003 after the completion of all renovations. The automation control level was significantly improved after the renovation, and the water production capacity increased from an average of 120 m³/h to an average of 140-160 m³/h, fully guaranteeing the water needs of the six generator units. Due to the improved control level, the amount of wastewater generated during the water production process was significantly reduced, achieving certain environmental protection and energy-saving effects. The system's high reliability and intuitive operation reduced the number of people on duty in the control center from two to one, greatly saving labor costs. Since its completion, the system has operated reliably and significantly improved production efficiency, thus receiving high praise from users and frequently becoming a model for other power plants to visit and emulate. [b]References:[/b] 1. Yang Xianhui, *Fieldbus Technology and Application*, Tsinghua University Press; 2. Wu Kuanming, *Selected Applications of Fieldbus Technology*, Beijing University of Aeronautics and Astronautics Press; 3. Mawan Power Plant, *Operating Procedures for Chemical Makeup Water System*.