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For now, the most typical water plant control system (PLC + PC) has a three-layer structure.

1. The first layer is the information management layer, which is composed of automatic monitoring management computer, engineer operating station computer, video monitoring computer, Ethernet switch, DLP TV wall and other management computers.

2. The second layer is the control layer, which is composed of PLC master station and remote IO.

3. The third layer is the test execution layer, which includes the controlled device (object) and the test instrument.

There are two ways to connect the detection execution layer and the control layer:

1. One is that the controlled devices (objects) and detection instruments are in one-to-one correspondence with each control layer (PLC station I/O).

2. The other is to use remote I/O communication to collect the corresponding main information. The management computer and the PLC master station use Ethernet communication.

application solution

The water plant automatic control system adopts the hierarchical distributed structure network control mode. The control system is divided into a main control level (central control room) and a local control layer (sub-control station). Realize the monitoring, operation, control and network communication connection of the corresponding control layer equipment. The monitoring and management operation station system in the central control room completes the automatic control of the whole plant. Including two sets of monitoring stations, printers, and UPS power supplies that are mutually hot standby. The central control system is connected to each field control PLC station through industrial Ethernet and using optical cables. The two sets of workstations are equipped with thermal redundancy, and can focus on monitoring or configuration functions respectively. When the fault occurs, they are used as backups for each other, and the operation mode is flexible. An electric projection screen and projector have been set up in the central control room to display the whole plant process flow chart, main parameters and equipment operating status. Provide power backup protection for all equipment in the central control room through a large-capacity UPS. Each sub-control station is equipped with a set of PLC control cabinet. The cabinet includes programmable controller, operator interface HMI, power supply device, redundant fiber optic switch, power supply lightning protection overvoltage protection device, small circuit breaker, wiring terminal, small relay, installation connection cable and accessories. According to the process characteristics of the water plant, the layout of the structures and the distribution of on-site control, a PLC site sub-station is set up. The PLC site sub-station uses a programmable logic controller (PLC). The PLC is a modular structure. The hardware configuration is flexible and easy to expand. Software programming is convenient. And the PLC substation and the corresponding MCC are placed in the same place, saving the cable between them. When the monitoring workstation of the central control room is out of operation or the channel is faulty, the communication between the sub-control station control unit and the main control level monitoring workstation is interrupted. Each local control unit can operate independently, perform control and monitoring, and improve operational reliability.

1) Each branch control station is equipped with an industrial optical fiber switch to work with PLC

2) Redundant backup of ring network links 3) Network commissioning, fault diagnosis and troubleshooting