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ã€Keywords】 sequential control system sub-group equipment level SCS
Luohe Power Plant #1 unit was originally a double furnace smelting furnace designed by the Shanghai Boiler Plant in the 1970s, and the steam turbine is also the product of that era. Because the unit's control level, safety, and reliability can no longer meet the requirements of the grid peaking, the thermal efficiency of the unit is not high. For this reason, the provincial power company regards this unit as the key technical reform project this year. The reconstruction of the thermal control part is mainly the use of distributed control systems. DCS uses the XDPS-400 system from Xinhua Control Engineering Co., Ltd. The system includes: MCS, BMS, SCS, ECS, DAS, DEH, MEH seven subsystems.
The sequential control system (SCS) incorporates all auxiliary equipment and equipment of boilers and turbines and some auxiliary equipment of some generators into DCS control. The SCS has a total of 1797 I/O points, of which DI: 1171 points, DO: 592 points, and AI: 34 points. The design and configuration of the SCS was completed by the Anhui Electric Power Test Institute, and the commissioning work was undertaken by the Luohe Power Plant.
First, the control function 1, sequence control system sub-group design sub-group-level functional group design mainly focused on the boiler wind smoke system. For the boiler windy smoke system, most of the auxiliary equipment and equipment on the boiler side are centralized, the interlocking and protection conditions of the auxiliary machinery are numerous, the interlocking and protection conditions between the equipments are very complicated, and there are many startup and locking conditions, and the process flow is complicated. Complex, it is easy to cause misuse. Specifically included: blower A/B sequence control promoter group, induced draft fan A/B sequence control promoter group, air preparatory A/B sequence control promoter group, open channel A/B sequence control subgroup and wind smoke system A/ A total of 10 subgroup-level functional groups were included in the group B sequential promoter subgroup. In addition, two sets of sequential start/stop subgroups for the electric water pump were designed in the turbine section.
For simple process systems, such as open water, closed water, condensate, etc., if you design a subgroup-level sequence, there are only two or three steps. For this situation, we designed the device linkage function and also achieved the function of the sequence control subgroup. For example: After the condensate pump is started, the outlet door is linked, and the outlet door is automatically opened. The operator does not need to operate.
2. Sequential Control System Equipment Level Design For a single auxiliary machine and equipment, all can be operated on the CRT. It centralizes the protection and interlocking functions, and is also the interface of the operating personnel to the equipment operation. It is the core of the entire SCS system. It is also the focus of SCS design and debugging.
(1) The interlocking and protection logics are fully considered for auxiliary machines (air blowers, induced draft fans, air preheaters, electric pumps, etc.). It is necessary to ensure the safe operation of the auxiliary machine according to the data provided by the manufacturer, and to ensure the safe and stable production of the unit. Taking the wind-smoke system as an example, in order to ensure the safe and reliable operation of a single auxiliary machine and equipment, we considered the cross-operation mode, such as the operation of two air preheaters or A-air preheater, A-induced operation, and B-transmission operation; Two air preheaters or B air preheater operation, B induction operation, A delivery operation, etc. At the same time, some electrical interlocks were also designed. For example, when air preheaters, air blowers and induced draft fans are all in operation, an air preheater trips, and the induced draft fan and the blower on the same side of the joint jump; the air preheater, the blower and the induced draft fan are all in During operation, a draft fan trips, and the blower on the same side is jumped.
(2) For the boiler auxiliary engine oil system and the turbine engine side oil system, except for the turbine engine oil system, only the CRT start/stop and monitoring functions are designed, and the interlock function is completed by the electrical hard wiring circuit. The functions of other oil systems are implemented by SCS. .
(3) Perfect protection and interlocking functions have been designed for the body and pipeline's trapdoors of steam turbines and boiler steam feed pumps. In the normal start-up and shutdown of the unit, the operator does not need to intervene, and the hydrophobic door automatically switches according to various conditions. At the same time, each super-relaxation switch signal is designed as a pulse signal. When an emergency occurs, the operator can perform the CRT manual operation to ensure the safety of the system.
(4) All the analog protection signals, such as temperature, which participate in the protection, are designed with quality detection and disconnection protection function, which can prevent the protection signal from malfunctioning due to abnormal protection of the signal or loop.
3. Interfaces between SCS and other systems SCS controlled devices are numerous. The design of the interface signals directly relates to the smooth operation of SCS, and it also affects the safe operation of other systems.
(1) For the SCS signals used by other systems within the DCS, in view of the reliability of the DCS, all through the Internet communication, no longer according to the traditional hard-wired program. This saves a lot of system resources such as I/O channels.
(2) The CCS controls the front door to isolate the power door from the SCS. In addition to designing the CRT manual switch, the SCS also accepts CCS linkage signals. These linkage signals are designed as an over-relaxation function to ensure the correct operation of the isolated electric door in accordance with CCS requirements.
(3) SCS valve and solenoid valve DO output all use relay isolation (relay directly installed on the DO output terminal board) to ensure that the DCS system is isolated from the outside; for the auxiliary machine DO output, taking into account the capacity of the relay, the addition of large-capacity relay Cabinets are isolated.
Second, SCS configuration and debugging As mentioned before, XDPS-400 uses today's most popular US Microsoft's WINDOWSNT operating system, using a dedicated graphical configuration tool, human-machine interface is friendly, configuration, debugging and maintenance are extremely Convenience.
The SCS system of this unit is designed with two kinds of control: one is equipment level control, and is composed of equipment interlocking, protection and operation personnel's manual operation permission conditions. This part of the configuration is done by a combination of various function blocks. Different requirements for different equipment (such as degassing on, off-gassing, energized on, live off and single coil, double coil, etc.) can be achieved by selecting the working mode of DEVICE algorithm, and the modification is very convenient.
Another type of SCS control is sub-group level control. XDPS-400 specifically provides a stepping logic operation module: STEP, which provides a method for implementing group-level sequence control and sub-group-level sequence logic. Each STEP module can realize up to 8 steps of output, receive 8 complete signals, set the set time and limit time of each step, start, stop and reset, and output step (STEP) and step Sequence run time (TRUN), step time remaining (TRST), step sequence (RUN), step sequence completion (END) and step sequence failure (FAIL). If a subgroup-level sequential control exceeds 8 steps, multiple STEP modules can be connected in series. Because the implementation of the sub-group sequence control is often constrained by the controllability of the field equipment, so the transformation project of # 1 unit of Luohe Power Plant has designed more than ten sub-groups of sequence control according to the operation requirements and equipment conditions.
XDPS-400 graphics maker (Maker), operating system also uses WindowsNT or Windows95 or above environment.
Third, some views Through the design of the SCS system and the commissioning of multiple units of the sequence control system, there are several views on the sequential control system:
1. The start/stop of a relatively simple process system requires only two or three steps if the sub-group is designed. There is no need to reduce the number of operation steps and no sub-group-level sequence control is required. As long as the necessary equipment linkage logic is designed, it can also achieve the functions of the sequence control subgroup, and also obtain the role of ensuring the safe operation of the process system and reducing the labor intensity of the operating personnel.
2. For sub-group-level sequential control design, it is necessary to fully understand the process flow of the process system and the controllability of the controlled equipment. It is also necessary to clearly understand the operational procedures of the unit and the operating habits of the operating personnel. This is to design the sub-group-level sequence control. Can be accepted by the power plant operating personnel and thermal control maintenance personnel, has a very good practicality, but also can improve the operation rate of sub-group-level sequential control.
3, DCS's alarm window shows the scrolling alarm information, the operating operator is slightly inattentive, the alarm information will pass by. Therefore, the SCS screen should display various protection and interlocking alarm information. The operation screen should provide the operating operator with detailed operation instructions and help to prevent misoperation as much as possible.
4. For the control design of single/double solenoid valves, it must fully consider that the solenoid valve must move in the safe direction in order to protect the safety of the unit.
Fourth, the operation of the situation through the design and commissioning staff's efforts, the project design of 12 sub-group-level sequence control debugging and 168 hours trial production process can be successfully applied. The various protection and interlocking functions of the SCS have been put into use normally and there have been no mistakes or misrepresentations. In general, the design, construction and commissioning of the system were successful and the requirements for the unit transformation were met.
The pulverizing system of this unit adopts the intermediate storage type of powder feeding, and the start-stop of the pulverizing system is very complicated. The operation of wind exchange is very difficult, and misoperation may easily occur. In view of this situation, research and experiments on automatic air exchange in the pulverizing system are currently underway. Once the automatic wind exchange test is completed successfully, consideration can be given to increasing the design and testing of the group-level sequence control of the milling system.
From the current application of XDPS-400 in Luohe Power Plant #1, its hardware is mature and reliable. Its software is similar to the fool machine for users and debuggers, as long as it has a part of the basis of WINDOWS operating system, easy to learn and easy to use. It is very convenient to modify the download. It is also very convenient for the maintenance and transformation of thermal workers.
Design and Application of Sequence Control System for Unit #1 in Luohe Power Plant
Anhui Institute of Electric Power Experiment Zhang Zhenglin Luohe Power Plant Hu Gensheng Xie Ming [Abstract] This article describes the control strategy used in the design of the sequence control system for Unit 1 of Luohe Power Plant, as well as the configuration, commissioning and commissioning of the system. Some views were put forward on the design of the sequential control system.