IS200TSVCH2AED MRP246517 Circuit Board Assembly

Description

IS200TSVCH2AED MRP246517 Circuit Board Assembly

IS200TSVCH2AED MRP246517 Circuit Board Assembly

Overview of DCS System With the continuous improvement of unit capacity and operating parameters in thermal power plants, DCS has become increasingly important in production. Its safe and reliable operation is closely related to the safe and stable operation of the unit. Therefore, it is very necessary to analyze various problems that occur in the operation of the DCS system and take measures to improve the safety and reliability of the DCS system.

Distributed Control System, abbreviated as DCS, is widely used in production fields such as power, petroleum, chemical, metallurgy, light industry, etc. at home and abroad, especially in large power generation units. 2. The fault situation of DCS during the production process varies among different brands of DCS, and their fault phenomena and solutions are also different. However, they can be summarized into three categories:
(1) The system itself has problems and malfunctions, including design and installation defects, software and hardware failures, etc;
(2) Faults caused by human factors;
(3) DCS malfunction caused by external environmental issues in the system.

Examples of problems and failures in the DCS system itself are common in the production process, mainly including system design and installation defects, controller (DPU or CPU) crashes, network disconnection and other faults, black screen in the operator station, network communication congestion, software defects, low system configuration, system interface issues, etc.

Power and grounding issues: The DCS power system of a certain power plant uses ABB Symphony III power supply, which is installed according to the grounding method of II power supply during infrastructure construction. Multiple DCS module failures, signal jumps, and hardware burns occurred after the unit was put into operation; During the construction period of a power plant in Henan, there were problems with the production and installation of the DCS grounding grid. After the system was running, there were periodic fluctuations in all temperature measurement points; A power plant’s control system on the turbine side failed due to loose power connections. Lesson learned: DCS does not have a good grounding system and reasonable cable shielding, which not only causes significant system interference, but also makes the control system prone to sending signals incorrectly and causing module damage. Therefore, the design and configuration of DCS power supply should be reasonable and have a certain margin; DCS grounding shall strictly comply with the technical requirements of the manufacturer (if there are no special instructions from the manufacturer, follow DL/T774 regulations).

System configuration issue: (1) Within 3 months of trial production of a 2 * 330MW unit in a power plant in Zhejiang, frequent DCS (T-ME/XP system) failures and crashes caused multiple unit shutdowns. After analysis, there are issues such as redundant switch configuration, mismatched hardware configuration, and high compliance rate of the lower level T-ME communication bus. (2) The DCS transformation of a 200MW unit in a certain power plant resulted in inaccurate calculation of system configuration load rate and in order to reduce investment, the technical indicators approached the allowable limit. During debugging, the load rate of some controllers exceeded 90%, and the response of some soft manual operations was close to 1 minute. The problem was only resolved after adding new configurations. (3) The historical station of the Xinhua XDPS-400 system of a 300MW unit in a certain power plant frequently crashes. After inspection, it was found that multiple programs such as historical data recording, virtual DPU, performance calculation, and reporting were running at the station. Reasonably allocate the program to other stations to solve the problem.

Controller (DPU or CPU) malfunction: The main CPU of the HIACS-5000CM operating system F3S1 of a 300MW unit in a certain power plant has malfunctioned, and the slave CPU has failed to switch to the main control, making the equipment inoperable. Perform online replacement steps on the faulty CPU until the power outage, and successfully switch from the CUP to the main control CPU. After replacing the faulty CPU, the system is functioning normally.

Network communication failure (1) In the early stage of ABB, a batch of SYMPHONY experienced inconsistent communication data between different controllers in the same PCU cabinet. After upgrading the firmware, the problem was resolved. (2) All control valves of the 600MW steam turbine in a certain power plant suddenly swung significantly. Upon inspection, it was found that the speed signal of the M5 controller had changed from 3000r/min to 0r/min, and there was a data loss phenomenon in communication between the M3 and M5 controllers, causing the control valves to swing significantly. Measures taken: Multiply the communication signals of the PCU control bus and increase the delay of the communication signals; Important communication signals adopt communication redundancy.

DCS software issue (1) During the DCS debugging process of a 300MW heating unit in a certain power plant, the quality parameters of the measurement points were not set, resulting in the measurement points being considered as bad quality only in the case of a broken line and not functioning as quality verification. (2) The logic of the deaerator water level control circuit in a certain power plant was copied and modified from the high pressure heater water level control logic. The modification process was incomplete, and the PID parameters were not adjusted according to the deaerator situation, resulting in divergent adjustment of the deaerator water valve during operation and deteriorating regulation quality. Action taken: Check the logic and reset the PID parameters.

System interface issue: There is only one electrical grid connection signal to DEH for a 200MW heating unit in a certain power plant. During normal operation of the unit, the auxiliary contact of the electrical grid connection trembled, causing the turbine to trip. Measures taken: Use shielded communication cables, increase redundant contact signals, and perform a 2-out-of-3 logic judgment.

Examples of DCS failures caused by human factors are also common in the production process. This includes incorrect operations, incomplete management systems, and failure to follow prescribed work steps.

The # 12DPU of the Xinhua XDPS system DEH in a certain power plant failed to follow the prescribed work steps, and it was replaced online using a small MEH system DPU spare. After replacing the DPU, only copy the logic without writing to the electronic disk. When Unit Maintenance # 12DPU became the main control, its logic was MEH logic instead of DEH logic, resulting in data flickering, abnormal screen display, and inability to operate at the human-machine interface station. After copying the DEH logic and writing to the disk, it is normal.
During the operation of a power plant unit, personnel mistakenly operated the DCS relay cabinet relay during defect handling, causing the induced draft fan to trip and the boiler to MFT; The DCS card of a certain power plant malfunctioned. During the process of replacing the card, the staff did not carefully check the equipment and the card jumper was incorrect, resulting in the newly replaced card being burned.
The management system of a certain power plant operator station is not strict, and the USB port and optical drive of the host are not effectively sealed. During the night shift, some operators use the operator station to play games and watch movies, resulting in the operator station crashing; The DCS system management system of a certain power plant is incomplete, and there are no regulations for software upgrades, backups, and other work. The software upgrade of the auxiliary network water treatment POK1 operator station was not backed up, and the hard drive of the station malfunctioned, causing system recovery and abnormal communication with the network.

The number of DCS failures caused by external environmental factors is relatively small, but it also occurs occasionally in the actual production process. Factors such as high environmental temperature, humidity, dust, and small animals can cause abnormalities. (1) The air duct of the electronic room in a certain power plant is located above the DPU cabinet. During the operation of the unit, fire water flows into the air duct, causing water to enter and burn out equipment such as the DPU and server, resulting in the unit being shut down. (2) The remote IO cabinet in the circulating water pump room of a certain power plant was not tightly sealed, causing mice to enter and construct a nest inside the cabinet, causing the remote IO to be disconnected from the network. (3) The electronic room of a certain power plant has poor sealing performance, with severe dust accumulation on cards and DPUs, resulting in multiple failures. After taking measures such as improving the sealing of electronic rooms and installing air conditioning, the faults were basically eliminated. 3. Many examples of DCS system fault prevention and maintenance measures indicate that in order to reduce the probability of DCS system faults, it is necessary to do a comprehensive job in DCS from selection design to operation, start and stop maintenance.

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