Application of SIMATIC S7-300 PLC in automatic monitoring system of drainage pump station

1. Overview

As the main facility of municipal construction and management projects, drainage pumping stations (hereinafter referred to as pumping stations) are responsible for the important task of urban drainage and waterlogging prevention. Judging from the current control and management of most domestic pump stations, they are still in a quite backward situation, which is very different from foreign countries. In terms of electrical control, the degree of automation monitoring is low, and most pumping stations only have single-stage conventional control. At the management level, most pump station management records and statistics are performed manually. There is no regionalized network for pump station control and management. With the rapid development of the national economy, higher requirements have been put forward for municipal construction and management. Therefore, it is necessary to transform and improve the control and management of existing pump stations. Develop the monitoring and management of unmanned pumping stations from abroad to achieve the purpose of reducing staff, increasing efficiency and improving management level. This project is targeted at the Tangqiao Pumping Station in Pudong New District, Shanghai, to transform the automated monitoring and management of the entire pumping station. ​

2. Overview of the working conditions of the pumping station Tangqiao Pumping Station is located on the Huangpu River on Tangqiao Road, Pudong New District, Shanghai. The pumping station is mainly used for sewage discharge treatment and flood control in nearby areas. The service area is 240 hectares and the total drainage is 13.8 m3/s.

2.1 Equipment Distribution Like most pumping stations, the equipment distribution plan is shown below (Figure 1).

① Inlet and outlet gate: used to prevent the Huangpu River water from flowing back and maintain the pumping station.

② Collection tank: The sewage from underground pipes is collected in this collection tank. The collection tank is divided into inner and outer areas by stainless steel grilles. After the sewage flows from the inner area through the grille and is decontaminated, it is discharged into the outer area into the Huangpu River. An ultrasonic liquid level meter is installed on the inner and outer sides of the water collection tank to detect the water level and water level difference between the inner and outer areas.

③ Decontamination machine: The pumping station is equipped with 2 wire rope traction grille decontamination machines. The decontamination machine is used to lift the garbage and dirt attached to the grille from the water collection tank for treatment.

④Transformer room: In order to ensure the reliable operation of the pump station, the pump station is equipped with two 800KVA power transformers. The power transformer is equipped with a temperature monitor to monitor the three-phase temperature. When the temperature exceeds the limit, it can automatically start the fan to cool down and alarm.

⑤Water pump room: Tangqiao pumping station is equipped with six 180 kW axial flow water pumps; a water level detector is installed in the water storage room.

⑥Control cabinet room: The room is equipped with 2 incoming line cabinets (cabinets 1, 13); 4 power factor compensation cabinets (cabinets 2, 3, 11, 12); pump switch cabinets (cabinets 4-6, 8-10) and 1 connecting cabinet (cabinet 7).
600)this.width=600″ border=0> 2.2 Control Requirements Taking Tangqiao Pumping Station as the facility object, carry out the transformation of automatic monitoring and management of the entire pumping station.

① Modify the water pump control switch cabinet of the pumping station to provide local and remote control functions.

② Transform the power factor compensation cabinet of the pumping station to realize local automatic compensation and remote power grid monitoring.

③ The transformer room of the pumping station is renovated to provide remote display, high temperature alarm and other functions for the three-phase temperature of transformers A, B and C;

④ Establish a control room for the pump station, implement three-level control of the pump station, and set up an automated monitoring console and signal processing cabinet in the control room.

⑤ Use SIEMENS’ S7-300 series PLC to realize automatic monitoring of the entire pump station. The water pump will automatically switch based on the pump status, water level, rainfall, power grid status, gate position and other working conditions.

⑥ By detecting the water level difference, it prompts or automatically switches on the decontamination machine.

⑦ Use a high-performance 10-inch true-color LCD touch screen to dynamically monitor and manage the entire pump station, provide fault alarms, record working conditions and print reports.

⑧ Reserved communication interface for regional monitoring and data transmission through telephone lines or DDN network. ​

3. Hardware system composition Based on the above requirements, we have developed the following automated monitoring system for Tangqiao Pumping Station. The structure of the system is shown in Figure 2. The main configuration is as follows. ​

3.1 PLC configuration The PLC of the pump station automation monitoring system adopts the S7-300 series of SIEMENS. According to the system requirements, the overall PLC configuration is as follows:

① Central processing module (CPU): Select CPU314, and the memory RAM is expanded to 64K.

②Digital input module (DI): Choose SM321, a total of 8 blocks (16 points/block). Processes 128 points of input signals. ​

③ Digital output module (DO): Choose SM322, 4 blocks are 16 points/block, 4 blocks are 8 points/block. Processes 96 points of output signals.

④ Analog input module (AI): Choose SM331, a total of 3 blocks (8 points/block). Processes 24 input signals. ​

⑤ Communication module: Choose CP340, 2 modules in total, 1 module is RS232 interface and 1 module is RS485 interface. The PLC uses four frames, three of which are in the RTU signal cabinet, one of which is a spare expansion frame; the other is in the console and is connected through the IM361 expansion, which simplifies the wiring and greatly improves reliability.

3.2 Touch screen configuration The touch screen uses the 570 HMI of Japanese DIL Company (SIEMENS did not have such HMI at the time) to achieve the above requirements. The HMI is connected to the CP340 of the PLC through the RS232 interface, and the communication is completed using the SIEMENS 3964R protocol. 3.3 Grid monitoring configuration The grid monitoring adopts the DIRIS M type power monitor of the French SOCOMEC company, which can detect the phase voltage, line voltage, phase current, neutral current, active and reactive power, and power factor of the three-phase four-wire system. frequency and corresponding maximum value. The monitor uses the RS485 interface to connect to the CP340 of the PLC using the MODBUS protocol to transmit power grid monitoring data. Because the pumping station uses dual power grid incoming lines, two sets of power monitors are used, which are installed on the incoming line cabinets on both sides. The signals of other devices are connected to the PLC through digital or analog points.

Software monitoring implementation

The software of the Tangqiao Pumping Station Automation Monitoring System mainly consists of two parts: PLC monitoring software and touch screen graphic control software. PLC monitoring software consists of several major modules. ​

4.1 System detection and fault handling module

The system detects and processes all input signals and responds differently depending on the situation. The processed signals include: the temperature and vibration of six pump motors; the status of the inlet and outlet gates; the liquid level in the water storage room; fire and anti-theft safety; the temperature of two power transformers; rainfall; the operating conditions of four power factor compensation cabinets; the operating conditions of the power grid ( Voltage undervoltage and overvoltage monitoring; three-phase current overload monitoring; phase loss monitoring; three-phase unbalance monitoring; power overload monitoring; power factor monitoring; power accumulation); sewage pool water level, etc. System faults are classified into three levels: Level 1 fault is defined as the highest level. When such a fault occurs, all control outputs will be disabled. Sound and light alarm, record printing, fault type and solution displayed on the display screen. Only after troubleshooting and pressing the manual reset button does the system resume normal operation. Secondary faults are defined as secondary. When such a fault occurs, the control output of the fault point will be disabled, and the system will automatically adjust and continue the current operation. Fault alarm and recovery are at the same level of fault. Level three faults are defined as the lowest level. When such a fault occurs, only audible and visual warnings will be given without interrupting the current operation. Implement relevant fault sound and light alarms and records according to various faults occurring in the system. At this moment, the touch screen enters the fault alarm screen, displays the fault content, nature, location, time and solution, and prints it. ​

4.2 Operation and processing of decontamination machines and drainage pumps There are two decontamination machines in the pumping station, and the system monitors the working conditions of the decontamination machines. When the fault signal is set, a secondary fault alarm is set, which is processed by the <system fault processing> module. Light up or turn off the relevant indicator lights according to the signal status. The machine is displayed on the touch screen at the same time. When the selector switch on the decontamination cabinet selects remote control, the console will perform the decontamination operation before the pump automatically runs. If water level difference detection is adopted, automatic sewage discharge will be implemented according to the water level difference mark. During automatic sewage discharge, a sound and light warning is given on site first, and then the device is operated. ​​​​

There are six pump starting cabinets connected to the operating console for control. ​

①When the fault signal is set, a secondary fault alarm is set, which is processed by the <system fault processing> module. ​

② Turn on or off the relevant indicator lights according to the signal status. ​

③When the selector switch on the pump switch cabinet selects remote control, four pump operation modes can be implemented on the operating console: manual mode; automatic mode; pre-evacuation mode; maintenance mode. ​

④ Each pump is equipped with its own status indicator light on the operating table; manual operation buttons and selector switches.

⑤The selector switch of a single pump has four levels: stop; maintenance; manual and automatic. When setting the manual gear, manual or pre-evacuation operation can be implemented. In automatic mode, the pump is allowed to enter the system automatic operation configuration. ​

⑥ There are three selector switches for system operation: stop; automatic and pre-evacuation. <Stop> prohibits the operation of all pumps; <Auto> allows a single pump with the selector switch set to the automatic gear to enter the automatic operation configuration. <Pre-evacuation> allows the pre-evacuation operation of a single pump with the selector switch set to manual gear. ​

⑦The starting and stopping of the pump should be delayed and put in and out in sequence. ​

⑧Basic interlocking conditions for pumps: A. Level one failure, power failure prohibits the operation of all pumps; B. Pump motor failure, pump starting cabinet failure prohibits the operation of the corresponding pump; C. Different operations of the pump must comply with the above pump starting cabinet, Correct settings between operating consoles; D. Water level interlocking. ​

⑨When the above different interlocking conditions are met, the pump can enter manual, maintenance, pre-evacuation or automatic operation.

⑩ When the pump is running automatically, the number of pumps to be run must be determined based on the water level point and water level zone; determine whether the pumps that can be put into automatic configuration meet the above requirements. If not, a fault alarm will occur; if there are too many pumps that can be configured For the pumps that need to be put into operation, the pumps with the smaller cumulative running time of these pumps will be put into operation. As the water level decreases, phase out the pump currently running the longest. ​

4.3 Data processing and human-computer interface processing

①Data statistics: AC contactor action count of the pump stamping cabinet; cumulative pump running time; cumulative drainage volume of the pumping station; cumulative rainfall; cumulative power consumption.

②Data settings: water level value, water level difference and flow value settings; transformer temperature and gas value settings;