Abstract: This article analyzes the common faults and causes of DCS systems in the operation of thermal power plants, and proposes targeted measures for handling faults when they occur. This can provide reference for the operation of DCS systems in thermal power plants and the practical application of operators in their work.
As the leading factor in the safe and economic operation of thermal power plants, the DCS system of thermal control automation equipment has been widely applied in recent years, playing a positive role in the safe and stable operation of thermal power plant units. However, the safety and reliability of DCS systems still need to be improved. During operation, various faults often occur, which lead to unplanned shutdowns of power generation units and cause undue losses to power generation enterprises.
1. Common faults in DCS systemsWith the continuous rise of industrial production automation and the increasing complexity of process control requirements, a comprehensive control system – DCS system – has emerged. Due to the current limitations in the application level of DCS systems in various thermal power plants, it is inevitable that the system will malfunction during operation. Common DCS system failures include power system failures, hardware (module) failures, system software failures, and communication network system failures.
1.1 Power system failure
Power failure is a fatal failure of the DCS system. Once a power failure occurs, not only will the entire system stop running, but it will also cause the unit to trip, resulting in unplanned shutdowns.
1.1.1 Main causes of power system failures
There are many issues with power supply. Firstly, the backup power supply cannot be switched on automatically. Although the UPS and APS dual backup power supply method is used, there may be instantaneous power loss during conversion, leading to unit tripping; The second reason is that the unreasonable insurance configuration and internal faults of the DPU power supply cause power interruption, leading to the cessation of system operation; The third reason is that the fluctuation of the stabilized power supply causes protection misoperation and poor contact of the plug, resulting in no output of the stabilized power supply; Fourthly, in some systems, the entire cabinet is supplied with a single fuse for all input signals or a single power supply with a large external load, resulting in module damage; The fifth issue is that the system power supply is not powered by UPS, making it even more difficult to talk about redundant backup.
1.1.2 Preventive measures to be taken for power system failures
To ensure the safety and stability of the DCS system, it is necessary to first have a reasonable power supply layout, then choose high-quality power modules, and ensure a high redundancy rate. Once again, pay attention to observing the output voltage of the power supply to prevent fluctuations. The fourth is to implement lifespan management for the power supply, which must be replaced when necessary. It is absolutely not allowed to wait until the power supply malfunctions before replacement.
1.2 Hardware (Module) Failure
The hardware (module) components of DCS system can be divided into three major parts: processor module, I/O module, and communication module. The functions of these three modules are different, and common fault areas are process channels and human-machine interfaces.
1.2.1 The main causes of hardware (module) failures
① Process channel failure, also known as I/O card failure. The first cause of I/O card failure is the aging and damage of the card due to long-term operation. This type of operation is generally hidden, and the system will only sound an alarm if there are abnormal parameters; The second aspect is that loose connection wires cause communication interruption between some I/O modules and the host. In this case, the system will immediately respond and an alarm will appear; The third aspect is the occurrence of channel failures due to interference caused by external strong electrical signals entering.
② Phenomena such as malfunction and effectiveness of ball markers and control operations, as well as operator station crashes, keyboard and printer malfunctions, all belong to human-machine interface failures.
The reasons for the malfunction of the ball mark operation include aging of the device due to long-term operation or contamination by floating dust or oil, which prevents the contacts from making and breaking on their own, or poor contact of the cable plug causing communication interruption with the host.
The main reason for controlling the effectiveness of operation is that the operation signal of the ball mark cannot change the state of the process channel. There are three possibilities: firstly, there may be a hardware failure in the process channel; The second possibility is a defect in the software used by the operator station; The third issue is that the device is overloaded or opens too many windows, resulting in unresponsiveness.
The reason for the operator station crashing is basically the same as the reason for the control operation failure.
The reasons for abnormal keyboard operation include: keyboard configuration errors, poor contact, loose connection cables, or accidentally moving the keyboard when starting the host, resulting in missing startup.
The reason for abnormal operation of the printer is either due to improper configuration or due to shielding the printer.