Application of NA400 programmable controller in au

  • Detail

NA400 programmable controller application scheme for auxiliary control system of thermal power plant I. Introduction the auxiliary system of thermal power plant is an important part of thermal power plant and a key component of power plant operation. It mainly includes coal handling system, ash/slag removal system, chemical water treatment system, etc., referred to as "ash water". In order to improve the control level, control mode, safety and economy of system operation of the auxiliary system of the whole plant, realize local unattended operation of the auxiliary workshop, improve labor productivity and automation level of the whole plant, the auxiliary system of the power plant will generally implement centralized monitoring of the whole plant, and establish public auxiliary, laying a good foundation for the realization of SIS of the power plant

II. System introduction

the auxiliary control system of the whole thermal power plant is mainly divided into three subsystems: water treatment control system, ash removal control system and coal handling program control system

1. Power plant water treatment control system

this system is mainly applicable to the control and monitoring of boiler make-up water, condensate, circulating water, industrial wastewater and unit drainage systems in thermal power plants

the industrial water treatment system adopts the local unattended mode. The PLC main cabinet is arranged in the boiler make-up water control room, and the remote station is placed in the industrial wastewater workshop. 3. Move the limit clamp of the extension ruler to contact the pointer of the extension ruler. The control system is connected to the water system control through the redundant two-way communication interface. Through the water system operator station of the whole plant, it completes the data acquisition, program start/stop, interrupt control (automatic step control, semi-automatic step control and skip control) and single equipment operation, system configuration and other functional monitoring of the fire pump room (including the water storage tank), drainage pump room, industrial wastewater, domestic sewage and other program-controlled systems, Alarm, emergency treatment and interlock protection shall be provided in case of abnormal operation conditions of the process system

the control device of the industrial water treatment system includes the process system program control operation, stop and automatic/semi-automatic startup of another standby device program. For sequence control, set step-by-step operation, group operation or separate operation, and have skip, interrupt and other operation functions. It is also provided with program step time and status indicating the new low expansion superalloy with intermetallic compound 'phase (ni3alti) as the strengthened phase, fault cause display, and necessary selection and interlocking functions

program control and manual dosing

the oily sewage treatment system is required to automatically start and stop according to the liquid level of the oily sewage collection tank

the sludge conveying and dewatering system can automatically start and stop according to the liquid level in the mud pit. The equipment includes mud pit, mud transfer pump, dehydrator, etc

the pumps are interlocked with each other and with the liquid level of acid storage tank, and the pump is stopped at low level

the water level controls the start of the intake pump; Start the pump at high liquid level and stop the pump at low liquid level

pump switching (accumulated running time)

switching of fan (the smoke generation of PP sample containing FP ⑵ 000 series flame retardant has decreased by 99% and the accumulated running time)

pump low level protection control

equipment fault alarm

the control system mainly includes data acquisition and sequence control functions. The LCD screen can display the process flow, measurement parameters, operation display, control object operation status, and group parameters. In case of parameter out of limit alarm or control object fault or state change, it can be automatically displayed in different colors on the current screen with audible prompt. The LCD screen can regularly print and record the monitored signals, alarm records of parameter out of limit, equipment operation records, etc. Program control and remote manual operation of the whole system are carried out through PLC, and necessary protection and interlocking are set in PLC

2. Ash and slag removal control system of power plant

ash and slag removal control system is divided into water flushing and pneumatic ash removal according to its working mode

ash handling control system function

= centralized monitoring and alarm function

= voice alarm function

= management report function

= interface function with plant level management information system (MIS)

= safety management function of the system

= equipment management function

the ash handling control system performs data collection and system control. The ash removal control system will be able to conduct centralized monitoring, management and automatic sequence control on the operation, start-up, stop and failure of the whole boiler pneumatic ash removal conveying system, ash silo, ash removal air compressor system and gasification fan room, and realize remote manual operation

the ash handling control system uses the LCD operation station as the operator's human-computer interface station to monitor and control the whole system through the LCD screen and mouse, and conventional instrument panel and simulation screen are no longer set. All operating parameters and alarm signals can be printed and recorded

for the controlled objects such as pumps, fans and valves, in addition to monitoring on the LCD of the operator station in the ash handling control room, they can also be controlled locally on the control switch on MCC or the button on the electric device of the valve, and the pneumatic valve can be controlled locally on the button installed on the solenoid valve box (supplied with the process system); The remote/local switching function can be realized in MCC and solenoid valve box, and the "in local control" signal is output to the control system

the ash handling control system adopts the control mode of combining automatic program control, remote manual operation and local operation. The program control can be provided with automatic, step-by-step operation, group operation or separate operation, and has operation functions such as step skipping, interruption or bypass. It will also be provided with necessary step time and status indication, selection and locking functions

each auxiliary control system can be monitored by the operator station of the auxiliary workshop set in the central control room to monitor the process and operating conditions of the corresponding system, and realize unattended operation locally. Redundant communication interface with DCS is reserved for centralized monitoring of auxiliary workshop to realize DCS monitoring of auxiliary workshop

3. Coal handling program control system

coal handling control system function:

system fixed program start and stop function

system combined program start and stop function

equipment one-to-one interlocking start and stop function

automatic coal blending function of raw coal bunker

local interlocking release control function

anti jamming function of three-way baffle and electric push rod of coal plough, etc.

coal handling program control system can complete coal feeding and coal blending control during normal operation of power plant; The coal handling equipment has the functions of monitoring the operation status, safety interlocking and protection, and monitoring and controlling the relevant power supply of the coal handling system. The coal handling program control system can communicate with the auxiliary workshop control system so that the coal handling system can be monitored in the main control room. 10/100m redundant Industrial Ethernet connection is adopted between the two systems. The coal handling program control manufacturer provides redundant optical fiber communication interface and provides corresponding data required for communication, including software, etc. The coal handling program control system can complete the interlocking and communication interface with the coal handling broadcast call system and the coal handling closed-circuit industrial television system. The system can control the start and stop of the main equipment of the coal handling system on the upper computer. It is equipped with a start warning system, a fault audible and visual alarm system, and has the functions of fault display and light inspection. It can display the operation status of belt and telescopic belt, status indication of coal crusher, coal screen and other equipment, fault location and nature, and high and low coal level display of coal bunker

the coal feeding control function of the system is divided into three modes: automatic, manual and local

coal blending control functions are divided into Program-Controlled Coal Blending and manual coal blending

in the accident alarm function, the system has perfect accident alarm function. When an accident occurs, the voice alarm system will send a voice signal when its value is the average of the measured values of all samples in a group of samples. At the same time, the CRT screen displays the flow chart of the fault area, the graphics of the accident equipment change color, and the nature and time of the fault are displayed in Chinese on the top of the screen. The fault alarm system has the functions of voice alarm, real-time alarm query, historical alarm query, classified alarm query and alarm printing

management and monitoring function means that the whole coal handling system has a computer management function, which can automatically collect operating conditions and relevant data, realize real-time flow preparation, modification and status display, and has a tabulation function, can print various reports according to the specified time or call, and can query and call relevant data on CRT. The report has the functions of equipment operation time recording, operation time history query, coal quantity statistics, process recording, etc

III. solution

through the analysis and research of the above auxiliary control system, the following system solution is conceived and designed based on the principle of striving for cost performance, stability and perfect function. The system network structure diagram is as follows:

system structure

the system uses NA400 series PLC as the control station, which are water treatment control system, ash removal control system and coal handling program control system respectively. Each control station is equipped with two Ethernet switches, which form a redundant ring with two industrial Ethernet switches of the backbone. Each control station is equipped with an engineer station and an operator station, and the centralized control room is equipped with an engineer station, an operator station and a redundant server

· control system

na400 CPU adopts Intel Pentium chip and integrates two Ethernet tcp/ip communication interfaces, eliminating communication module, saving cost and facilitating group. Modular structure, easy installation and replacement, can be installed at any position of the rack. No expansion module is required for rack expansion, and one bus cable can realize the expansion of i/o

the full intelligent i/o design and a series of safety and reliability designs provide guarantee for the safe and reliable operation of the system. NA400 adopts the field bus network, which not only has the characteristics of fast communication rate, strong anti-interference ability, low cost, simple structure and good real-time performance, but also has good scalability, is easy to realize the flexible configuration of modules, and greatly improves the adaptability to the environment and installation requirements. It integrates all five programming languages of IEC and the original sequence control diagram language. Various languages are called among programs, making programming more flexible and convenient and meeting the requirements of a variety of complex working conditions. The Ethernet communication interface provided can realize remote programming and debugging, and meet the modification and maintenance of the control process of the field control device in the remote control center

· network structure

the whole auxiliary control network adopts modular industrial switches, of which the backbone switches are redundant. The industrial Ethernet ring is established by using multi-mode optical cables and industrial grade switches. The unified network platform and software platform are used to interconnect different auxiliary control systems, so as to realize the relatively centralized control of peripheral auxiliary control systems. The whole auxiliary control network adopts the star ring hybrid structure, connects each auxiliary control system with Ethernet ring, and is divided into trunk and sub ring. Each auxiliary control system is connected to the backbone in a star mode. The backbone adopts super redundant ring technology. When a point of the ring fails, the system can

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