Application of PLC in mine main drainage control s

The application of PLC in the mine main drainage control system

adopting PLC to automatically detect the water level and other parameters of the water bunker, according to the water level of the water bunker, the mine power consumption information and other factors, establish a mathematical model, and reasonably dispatch the operation of the water pump, which can achieve the purpose of avoiding peak and filling valley and saving energy. This paper introduces the composition, functions, characteristics and application of PLC in the underground main drainage control system of Daizhuang coal mine

1. Overview

with the rapid development of computer control technology, programmable logic controller (PLC) control with microprocessor as the core has gradually replaced relay control and is widely used in the field of automatic control in all walks of life. The coal industry is no exception, but at present, the main drainage system in coal mines is still controlled by relays. The start and stop of water pumps and the signal transmission pressure are adopted. When the sample breaks, it will automatically stop and save the maximum breaking strength value The instrument is easy to operate and has high test accuracy. The experimental results are printed out by a micro printer and the selection and switching are completed manually. It is not possible to automatically start and stop the water pump according to the water level or other parameters, which will seriously affect the management level of the underground main drainage pump room and the improvement of economic benefits

Daizhuang coal mine is a modern mine with a production capacity of 1.8MT/A, which was designed and completed in 1999. The underground water inflow is large, and five MDS are designed and installed in the central pump × 9 main drainage pump, supporting motor 1250KW, 3 drainage pipelines. During normal water inrush, two are in operation, two are for standby and one is for maintenance. In view of the progressiveness and reliability of PLC, Handan Design Institute of coal industry has implemented PLC automatic control, automatic detection and dynamic display of operating parameters for five main drainage pumps and their auxiliary vacuum pumping systems and pipeline electric valves, and transmitted the data to the ground production scheduling center for real-time monitoring and alarm display

by detecting the water level and other parameters of the water sump, the system controls the water pumps to work in turn and start the standby pumps in time, and reasonably schedules the operation of five water pumps. Through the touch screen, the system visually, visually and in real time reflects the working state of the system and parameters such as the water level of the water bunker, the working current of the motor, the motor temperature, the bearing temperature, and the flow of three drainage pipes through graphics, images, data, text, etc., and realizes data exchange with the integrated monitoring host through the communication module. The system has the characteristics of reliable operation, convenient operation, high degree of automation, and can save the running cost of the water pump

2. System composition

the automatic control system of the underground main drainage pump in the central pump room of Daizhuang coal mine is composed of five parts: automatic data acquisition, automatic rotation, automatic control, dynamic display, fault recording, alarm and communication interface

2, 1 automatic data acquisition and detection

automatic data acquisition and detection are mainly divided into two categories: analog data and digital data

the data of analog quantity detection mainly include: water level in the sump, working current of the motor, shaft temperature of the water pump, motor temperature, yield strength, tensile (compression, bending) strength, elongation, non proportional strength, elastic modulus and other parameters of the materials that can be detected in three drainage pipe flows; The data of digital quantity detection mainly include: the state of vacuum circuit breaker and reactor cabinet vacuum contactor of high-voltage starting cabinet of water pump, the working state and opening and closing position of electric valve, the working state of vacuum pump, the state of solenoid valve, the vacuum degree of water pump suction pipe and the pressure of water pump outlet

the automatic data acquisition is mainly realized by PLC. The PLC Analog input module continuously detects the water level of the water sump through the sensor, converts and processes the water level change signal, and calculates the rising rate of the water level in different water levels per unit time, so as to judge the water inflow of the mine and control the start and stop of the drainage pump. Sensors and transmitters such as motor current, water pump shaft temperature, motor temperature, drainage pipe flow, etc. are mainly used to monitor the operating conditions of water pumps and motors, and alarm when the limit is exceeded, so as to avoid damage to water pumps and motors. The digital input module of PLC collects various switching signals into PLC as the condition and basis of logic processing to control the start and stop of drainage pump

in the process of data acquisition, the processing of analog signals is to convert analog signals into digital signals (a/d conversion), and the conversion speed is determined by the sampling law. Generally, the sampling frequency should be more than 2 times of the highest frequency component in the analog signal, so that the accuracy of the a/d transformation can be completely restored to the original analog signal accuracy. The accuracy of a/d conversion depends on the number of bits of the a/d converter. For example, when the 5V voltage is required to be converted with the accuracy of 5mv, the accuracy is 5mv/5v=0.1%, that is, when the 1/1000 decimal 1000 is expressed in binary, it is required to be 10 bits, while the resolution of the a/d module used in this system is 16bit, and its accuracy is more than ± 0.05%, which is enough to meet the requirements of the control system. At the same time, the a/d modules used by PLC are transformed in the form of integration, which can make the input used to detect whether their products meet the national standard signal. The peak noise and induced noise are averaged, which is suitable for industrial places with serious noise

2, 2 automatic rotation work

in order to prevent the motor and electrical equipment from being damped or other faults not found in time due to the long-term use of the standby pump and its electrical equipment or standby pipeline, when the emergency failure of the working pump requires the standby pump to be put into operation, but it cannot be put into operation in time, so as to affect the mine safety, this system program designs the automatic rotation work control of five pumps, The control program automatically records and accumulates the parameters such as the number of starts and stops of the water pump and the operation time, the number of uses and flow of the pipeline, and the system automatically starts and stops the water pump and the corresponding pipeline in a certain order according to these operation parameters, so that the utilization rate of each water pump and its pipeline is evenly distributed. When a pump or its valve fails or a pipeline leaks water, the system automatically sends an audible and visual alarm, and dynamically flashes on the touch screen to record the accident, At the same time, the fault pump or pipeline will be automatically removed from the rotation work, and the rest of the pumps and pipelines will continue to work automatically in a certain order, so as to achieve the purpose of early detection and early treatment of faults, so as not to affect the safety production of the mine

2, 3 automatic control

the system control design selects c200he PLC of OMRON company of Japan as the control host. The machine is a modular structure, which is composed of PLC rack, CPU, digital i/o, analog input, power supply, communication and other modules. The PLC automatic control system establishes a mathematical model, reasonably schedules the water pumps, automatically and accurately sends the commands to start and stop the water pumps, and controls the operation of five water pumps according to the factors such as the water level of the sump, the high and low peaks of the underground power load, and the time period of the power supply price of the flat section, valley section and peak section specified by the power supply department (the time period can be adjusted and set on the touch screen at any time according to the actual situation)

in order to ensure underground safety production and reliable operation of the system, the water level signal is a very important parameter of pump automation. Therefore, the system is equipped with two sets of water level sensors, analog and switching sensors, both of which are set in the drainage and distribution bin of the water bin. The PLC divides the received analog water level signal into several water levels and calculates the rising rate of water levels in different water levels in a unit time, So as to judge the water inflow of the mine, detect the underground power supply current value, and calculate the power load rate. According to the water inflow and power load of the mine, control to start the water pump when the power consumption is low peak and the electricity price is the lowest in the day, and stop the water pump when the electricity consumption is high peak and the electricity price is high, so as to achieve the purpose of avoiding peak and filling valley and saving energy

2, 4 dynamic display

dynamic analog display adopts gp-570t touch industrial graphic display (touch screen) of Japanese digital company. The system dynamically displays the running state of water pump, vacuum pump, solenoid valve and electric valve through graphics, and uses changing graphic color and flashing function to give an accident alarm. Visually display the opening and closing positions of solenoid valves and electric valves, and display the vacuum pumping condition and pressure value of the water pump in real time

use graphic filling, trend chart, bar chart and digital form to accurately and real-time display the water level of the water sump, and send a warning signal and a segmented alarm for the water level of the low section, ultra-low section, high section and ultra-high section at the water level section of the start and stop pump, and use different audio forms to remind the staff of their attention

use graphics, trend charts and digital forms to visually display the instantaneous flow and cumulative flow of the three pipelines, dynamically display and alarm the monitoring amount of underground power load, motor current, instantaneous load and cumulative load of water pump, shaft temperature of water pump, motor temperature, etc., and automatically record the historical data such as fault type and time, The latest three faults (the number of fault displays can be set on the touch screen) are displayed circularly at the bottom of the screen to remind the staff to repair in time to avoid damage to the water pump and motor

2, 5 communication interfaces

plc carries out full duplex communication with the touch screen through the communication interface and communication protocol, transmits the working state and operating parameters of the water pump unit to the touch screen, and completes the dynamic display of each data; At the same time, the operator can also use the touch screen to transmit the operation instructions to the PLC to control the operation of the water pump. At the same time, PLC transmits the operation status and parameters of the water pump unit to the host of the ground production dispatching and monitoring center through the safety production monitoring system substation, which is connected with the safety production monitoring system of the whole mine. The management personnel can master all the detection data and working status of the underground main drainage system equipment on the ground, and can realize the telemetering and remote control of the underground main drainage system according to the automatic control information, and provide the production decision-making information for the mine leaders. Both the touch screen and the monitoring host can dynamically display the simulation diagram and operation parameter diagram of the operation of the main drainage system, record the system operation and fault data, and display the fault points to remind the operators to pay attention

3. System functions and features

(1) the PLC control program adopts a modular structure, and the system can be debugged and run in sections according to the program module. The program structure is clear, simple, easy to understand, easy to simulate debugging, fast running speed and so on

(2) according to the principle of water level and pressure control, the system automatically realizes the rotation of water pumps and extends the service life of water pumps

(3) the system can automatically select to start the nearest vacuum pump according to the position of the pump set in operation. If the vacuum degree cannot be reached within the time set by the program, the standby vacuum pump will be automatically started

(4) the system determines the time of starting and stopping the water pump according to the electric load and the time period of power supply price in the flat section, valley section and peak section specified by the power supply department, based on the principle of "avoiding peak and filling valley", so as to make rational use of electric information and improve the quality of electric operation of the mine

(5) PLC automatically detects the water level signal, calculates the rising rate of water level in different water levels in unit time, so as to judge the water inflow of the mine, automatically input and exit the number of water pumps, and reasonably dispatch the operation of water pumps

(6) dynamically monitor the operation status of the water pump and its auxiliary equipment on the touch screen, display parameters such as water level, flow, pressure, temperature, current and voltage in real time, alarm when the limit is exceeded, the fault screen will pop up automatically, and the fault point will flash automatically. It has the functions of fault record, historical data query, etc

(7) the system has communication interface function. PLC can communicate with touch screen and ground monitoring host at the same time, transmit data, exchange information, and realize telemetry and remote control function

(8) the system protection functions are as follows

overtemperature protection: when the water pump operates for a long time, when the bearing temperature or stator temperature exceeds the allowable value, the over limit alarm is realized through the temperature protection device and PLC

flow protection: when the water pump starts or operates normally,