1. Common faults in DCS systems
With the continuous development of industrial production automation and the increasingly complex process control requirements, an integrated control system, the DCS system, was born. Due to the current restrictions on the application level of DCS systems in various thermal power plants, it is inevitable that the system will malfunction during the operation. Common DCS system failures are: power system failure, hardware (module) failure, system software failure, and communication network system failure.
1.1 Power System Failure
A power failure is a fatal failure of the DCS system. Once the power supply fails, not only will the entire system stop running, but it will also cause the unit to trip, resulting in unplanned outages.
1.1.1 The main cause of power system failure
There are many problems in the power supply. First, the backup power supply cannot be self-injected. Although the UPS and APS dual-channel alternate power supply modes are used, there will be instantaneous power loss during the conversion, which will cause the unit to trip. Second, the insurance configuration is unreasonable. And the internal fault of the DPU power supply causes power interruption, which causes the system to stop running. Third, the power supply fluctuation causes the protection to malfunction and the plug is not in contact, resulting in no output of the regulated power supply. Fourth, some systems pass the insurance for all the entire cabinet. The input signal or one power supply has a large external load, which causes damage to the module. Fifth, the system power supply is not powered by the UPS, and redundant standby is even more difficult to talk about.
1.1.2 Precautions to be taken when the power system fails
To ensure the safety and stability of the DCS system, it is necessary to first have a reasonable power supply arrangement, and secondly to select a high-quality power supply module, and to ensure a high redundancy rate. Again, pay attention to the output voltage of the power supply to prevent fluctuations. The fourth is to implement life management on the power supply. The replacement must be replaced when it is replaced. It is absolutely not allowed to wait until the power supply fails.
1.2 hardware (module) failure
The hardware (module) card of DCS system can be divided into three parts: processor module, I/O module and communication module. The functions of these three modules are different. The common fault parts are process channel and people. Machine interface.
1.2.1 The main cause of hardware (module) failure
1 Process channel failure is also an I/O card failure. The first reason for the failure of the I/O card is that the card is aging and damaged due to long-term work. The occurrence of such work is generally hidden. Only when the parameter is abnormal, the system will alarm; Two aspects are that the loose connection line causes the communication between some I/O modules and the host computer to be interrupted. In this case, the system will react immediately and an alarm occurs; the third aspect is that the external strong electric signal breaks into the interference. Causes a channel failure to occur.
2 Failures such as the failure and effectiveness of the ball and control operations, as well as the crash of the operator station, and the malfunction of the keyboard and printer are all human interface failures.
The reason for the malfunction of the ball mark operation is that the device is aged due to long-time work or is polluted by dust or greasy, so that the contact cannot be turned on or off by itself, or the communication with the host is broken due to poor contact of the cable plug.
The main reason for the control operation effectiveness is that the operation signal of the ball mark cannot change the state of the process channel. There are three possibilities: one may be the failure of the process channel hardware; the second may be the defect of the software used by the operator station; the third is the device super Load or open the window too much, causing it to not respond.
The reason for the operator station crash is basically the same as the reason for the control operation failure.
The reason why the keyboard is not working properly is: the keyboard configuration is wrong, the contact is bad, the connection cable is loose, or the keyboard is accidentally activated when the host is started, resulting in a lack of startup.
The printer is not working properly: either the configuration is unreasonable or caused by shielding the printer.
1.2.2 Hardware (module) failure should take precautions:
In the operation process of the DCS system, in order to reduce the occurrence of hardware (module) failure, it is necessary to pay attention to the following points: provide a good operating environment for the hardware in strict accordance with relevant standards and regulations; the DPU of the master and the slave must not be manually switched. ; grounding should be good; avoid static induction; in the working state, should not open the cabinet at will, and should prohibit the use of high-power wireless devices in the vicinity, such as forbidden mobile phones and prohibit the use of walkie-talkies; keep the working voltage stable; for important The hardware (module) is configured with sufficient redundancy.
1.3 software failure
1.3.1 The main cause of software failure
Under normal circumstances, the cause of software failure is very simple, and the imperfection of the software itself is the main cause of the failure.
1.3.2 Precautions to be taken for software failure
Because the cause of the software failure is simple, then the method to prevent software failure is also very simple, that is to use genuine software, but remember to upgrade in time.
1.4 Communication network system failure
The communication network is the link between the DCS system and the production line. The faults generally occur on the node bus and the local bus, or it may be caused by landmark errors.
1.4.1 The main reason for the failure of the communication network system
1 node bus failure. When any of the bus's trunks are interrupted, it will cause communication failures of all stations and their sub-devices on the bus.
2 Local bus failure. Since the connected device is a primary component or control device that is directly related to the production process, the working environment is bad, the failure rate is high, and it is easily affected by the maintenance personnel to affect the production process. In addition, the bus itself can cause communication failures for various reasons.
3 address identification error. Whether it is a local component or a bus interface, once its address is incorrectly identified, it will inevitably cause disorder of the communication network.
1.4.2 Preventive measures for communication network system failure
To prevent the occurrence of communication network failures, the following must be done:
1 In order to avoid the occurrence of node bus failure, the most effective method is to adopt a dual redundant configuration mode to avoid the global impact caused by the failure of one bus.
2 An effective way to prevent local bus faults is to properly handle the connection point between the local bus and the local equipment. When disassembling the equipment, it must not affect the normal operation of the bus. The bus branch should be installed in a place that is not easy to touch. At the same time, the local bus is preferably configured with dual redundant configuration to improve the reliability of communication.
3 In order to avoid the occurrence of errors in address identification, it is mainly to prevent human error or mis-change.
2, the conclusion
The DCS system can effectively meet the needs of the control of each system of the power plant. Through the analysis of some major faults that are constantly exposed in practical applications, it can be summarized in time, so that relevant instrument control and maintenance personnel can find problems in time and make accurate judgments, and take correct measures. Countermeasures.
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