Abstract: Drainage pumping stations have significant drainage benefits in plain and lake areas. This paper introduces a computer monitoring system for drainage pumping stations based on Hollysys' LK series large redundant PLC. The system features redundant CPU, redundant power supply, redundant Ethernet, and redundant bus configurations. Communication with the host computer is achieved via Ethernet, ensuring real-time data transmission and stable, efficient operation of the control system.
Keywords: LK PLC; drainage pumping station computer monitoring system; redundancy system.
1 Overview
Drainage pumping stations are an important component of my country's water conservancy system. The construction of drainage pumping stations and their computer monitoring systems is crucial for the rational development, utilization, conservation, and protection of water resources, the prevention and control of floods, the sustainable use of water resources, and the transformation from traditional to modern water conservancy.
The drainage benefits of drainage pumping station projects are most significant in plain and lake areas, such as the Jianghan Plain in Hubei, the Pearl River Delta in Guangdong, the Sanjiang Plain in Northeast China, the Hangzhou-Jiaxing-Huzhou region in Zhejiang, and the surrounding areas of Dongting Lake, Poyang Lake, Taihu Lake, and Chaohu Lake.
In terms of agricultural drainage, taking Hubei Province, which has the largest drainage area and the largest installed capacity in China, as an example, it has successfully overcome seven major floods in the past thirty years. Among them, in the historically unprecedented catastrophic flood of 1991, drainage pumping stations played a crucial role, with a daily drainage volume of 420 million m³ and a cumulative drainage volume of nearly 10 billion m³ . That year, the pumping stations' flood control and disaster reduction benefits reached 16 billion yuan.
The drainage pumping station studied in this paper is a drainage pumping station in Hubei Province. This pumping station is a dike-mounted pumping station, consisting of 14 155kW water pumps, with a total installed capacity of 2175kW and a designed drainage capacity of 21m³ /s. This pumping station is a renovated station, and since its construction in 1976, it has been entirely manually controlled and cannot achieve remote monitoring.
2. Structure and Function of Computer Monitoring System for Drainage Pumping Stations
2.1 Composition of the Computer Monitoring System for Drainage Pumping Stations
The entire system consists of one supervisory control system and three local control units, as shown in Figure 1. Two monitoring computers are configured in the central control room, each equipped with monitoring configuration software, one printer for report printing, and one audible and visual alarm system for real-time fault alarms. In the local control units, one PLC and one touchscreen are installed for every seven units, and one PLC and one touchscreen are installed for the plant-wide common system. The PLCs in the local control units are Hollysys LK redundant systems. Each PLC consists of a power supply module, a redundant CPU, digital input/output modules, analog input/output modules, a communication module, and a backplane. The touchscreens are Hollysys HT6A00TE touchscreens used for monitoring field equipment.
Figure 1. Composition of the computer monitoring system for the drainage pumping station
2.2 Network Structure and Communication Method of Drainage Pumping Station Computer Monitoring System
The entire system's backbone transmission network adopts a 100Mbps industrial Ethernet network, supporting the IEEE 802.3 protocol and standard TCP/IP protocols; alternatively, an industrial-grade dedicated control LAN can be used. This control network features determinism, repeatability, and I/O sharing, enabling high-speed data transmission and real-time control. The transmission medium is Category 5 twisted-pair cable.
The LK unit communicates with the touchscreen via Ethernet, enabling local control of the unit. The LK backplane integrates a DP communication interface and is equipped with an LK239 serial communication module, making communication with third-party devices very convenient.
2.3 Functions of the Computer Monitoring System for Drainage Pumping Stations
The pump station computer monitoring system uses redundantly configured LK series large PLCs to effectively monitor and control all pump units and electrical systems in the station. It monitors, controls, interlocks, alarms, and prints reports on process parameters, electrical parameters, and equipment operating status. Through a series of communication chains, it performs the necessary data acquisition, data communication, sequence control, time control, loop regulation, and supervisory control functions for the entire process.
At the unit's local control unit, LK collects signals such as the operating status of the unit's auxiliary equipment and pump station motors, water level, temperature, voltage, and current via hardwiring. The control signals are mainly used to control the start and stop of the motors.
The local control unit for public equipment mainly collects information on the status of circuit breakers, the oil level and temperature of transformers, the upstream and downstream water levels of pumping stations, and fault, over-limit and over-range signals of some equipment, and controls circuit breakers and indicator lights.
3. Software Implementation of the Computer Monitoring System for Drainage Pumping Stations
3.1 Implementation of PLC Program for Drainage Pumping Station Computer Monitoring System
In the local control unit of the unit, since the capacity of each unit is small and it is a three-phase asynchronous motor, a soft starter is used for start-stop control. The local control unit PLC mainly realizes the start-stop control of the water pump.
Circuit breaker closing conditions: The remote/local switch is in the remote position, the inactivation/disable switch is in the activated position, the motor circuit breaker is in the open position, and the host computer issues a closing command.
The pump must be started under the following conditions: the remote/local switch is in the remote position, the inactivation/disable switch is in the activated position, the motor circuit breaker is in the closed position, and the host computer sends a start command.
The pump's start-up and reset conditions are: the soft starter maintains its start-up output for 20 seconds and the motor is in a running signal state.
Circuit breaker tripping conditions: The remote/local switch is in the remote position, the inactivation/disable switch is in the activated position, the motor circuit breaker is in the closed position, and the host computer issues a tripping command.
Figure 2. Ladder diagram program for basic start-stop control of water pump
Table 1 Control Points of Motor #1
Serial Number | Signal roll call | signal type | Signal meaning | Signal Status Description | |
0 | 1 | ||||
1 | SA1 | DI | Remote/local switching | remote | On the spot |
2 | SA2 | DI | Switching between enabling/disabling | prohibit | Investment |
3 | DJ1_YX | DI | #1 motor running signal | stop | run |
4 | QF1_H | DI | #1 motor circuit breaker closing position | Open position | Closing position |
5 | MID0 | COM | Remote start #1 soft starter | Invalid startup | start up |
6 | MID1 | COM | Remote control combined with No. 1 motor circuit breaker | Ineffective closing | Closing input |
7 | MID2 | COM | Remote control of No. 1 motor circuit breaker | Tripping ineffective | Trip output |
8 | MCD1 | COM | Motor #1 successfully started with soft start | invalid | Startup successful |
9 | MID21 | COM | Remote control stop #1 motor soft start | Stop invalid | Stop output |
10 | KO0 | DO | #1 motor soft start | Turn off output | Start output |
11 | KO1 | DO | No. 1 motor circuit breaker closing output | Ineffective closing | Closing output |
12 | KO2 | DO | #1 motor circuit breaker tripping output | Tripping ineffective | Trip output |
In the public local control unit, the main monitoring functions are the opening and closing of the two circuit breakers on the high-voltage side of the main transformer, the two circuit breakers on the low-voltage side of the main transformer, and the bus tie switch.
Circuit breaker closing conditions: The remote local switch is in the remote position, the inactive switch is in the active position, the circuit breaker is closed remotely, and the above three conditions are maintained for 1 second.
Circuit breaker tripping conditions: The remote local switch is in the remote position, the inactive switch is in the active position, the circuit breaker is tripped remotely, and the above three conditions are maintained for 1 second.
Figure 3. Ladder diagram program for circuit breaker closing and opening control
Table 2 Control Points of High-Voltage Circuit Breakers on the Main Transformer
Serial Number | Signal roll call | signal type | Signal meaning | Signal Status Description | |
0 | 1 | ||||
1 | SA1 | DI | Remote/local switching | remote | On the spot |
2 | SA2 | DI | Switching between enabling/disabling | prohibit | Investment |
3 | MID0 | COM | Remote control of the No. 1 main transformer high voltage side switch | Ineffective closing | Closing input |
4 | MID1 | COM | Remote control of the high-voltage side switch of main transformer #1 | Tripping ineffective | Trip input |
5 | KO0 | DO | No. 1 main transformer high voltage side switch closing output | Ineffective closing | Closing output |
6 | KO1 | DO | #1 Main Transformer High Voltage Side Switch Opening Output | Tripping ineffective | Trip output |
3.2 Implementation of PLC Program for Drainage Pumping Station Computer Monitoring System
The main functions implemented by the touch screen are: remotely monitoring the opening and closing status of each circuit breaker, remotely monitoring the operating status of each unit, remotely controlling the opening and closing of each circuit breaker, and remotely controlling the start and stop of each unit.
Figure 4 Unit operation control touch screen interface
Figure 5. Unit operation switch monitoring touch screen interface
Figure 6 Circuit breaker control touch screen interface
4. System Advantages
In current common pumping station configurations, computer monitoring systems tend to be overly sophisticated. Smaller units often employ the same configurations as large and medium-sized pumping stations, with each unit having its own local control unit and each control unit containing a PLC. This overly sophisticated configuration wastes power modules, cabinets, and building space, and complicates system networking, communication, data acquisition, and engineering debugging. Furthermore, it is incompatible with system safety requirements and actual conditions.
This system adopts a simplified redundant system configuration, with two redundant PLC controls configured for the 14 pump sets. This improves the safety performance of the control system and simplifies the system configuration. During unit operation, the system can achieve economical operation through programming, contributing to energy conservation and emission reduction in the pumping station.
The pump station computer monitoring system, which adopts Hollysys LK series large-scale PLC redundancy system, greatly improves system safety, simplifies system configuration, enables economical operation of the unit, achieves unattended operation, and improves work efficiency.
References
[1] Ge Qiang. Electrical relay protection and secondary circuit of pumping station [M], China Water Resources and Hydropower Press. 2010.
[2] Luan Hongru. Pumps and Pumping Stations [M], China Water Resources and Hydropower Press. 2009.
[3] Guo Xufang, Research and Application of Integrated Monitoring System for Pumping Stations [D], Southwest Jiaotong University. 2005.
[4] Wang Dingyi. Computer Monitoring and Control of Hydropower Plants [M]. Beijing: China Electric Power Press. 2001
[5] Hollysys. LK Large Programmable Controller Instruction Manual, 2008
[6] Yin Gang. Current Status, Problems and Development of Pumping Stations Nationwide [J], Hydropower Station and Pumping Station Automation Technology Consulting Network. 2010
First Author's Biography
Shi Liandong (1984-), male, holds a Master of Engineering degree and is a PLC industry technical manager with extensive experience in PLC control system hardware assembly, software programming, and on-site debugging. Currently, he is engaged in research on the application of PLCs in the water conservancy and hydropower industry.
