Hollysys DCS - DCS common communication faults and solutions

01 Node bus failure

The node bus material is usually coaxial cable, so as long as one cable is disconnected, the communication of all devices on the bus will be paralyzed, causing serious phenomena such as data loss, equipment stopdown, and operation interruption, which may eventually cause huge losses directly or indirectly. Frequent unplugging and unplugging of coaxial cables can lead to poor contact and signal interruption. Excessive contact resistance can also affect communication lines, and large data loads can lead to reduced data accuracy.

To solve this problem, a dual redundancy setup can be used, but the cable connection should be located behind the module to ensure that the coaxial cable is not adversely affected by mechanical operation. Plugging and unplugging is only carried out when the node bus is maintained, and multiple unplugging and unplugging is prohibited without other special circumstances. Make sure that the line contact resistance is at a normal level and check the line resistance regularly.

02 Fieldbus failure

The fieldbus material is twisted pair, and the equipment connected to the fieldbus is the first-line equipment of the production process, which can directly affect the production process. Because it is located in the nuclear power production site, the working environment is harsh, so it is greatly disturbed by various unfavorable factors, including the contact with it in the production process, and the influence of the environment and mechanical equipment will lead to the deformation of the fieldbus, coupled with the poor contact of the bus, so the possibility of failure is greater, and the impact on the DCS communication system is also greater.

Through the actual situation of the site, double redundancy settings can be adopted, and a pair of communication lines can be added to the interface to increase the reliability and accuracy of line transmission data. The connection between the fieldbus and the device is sensitive, so the connection must be reliable. When disassembling and installing the fieldbus, it is necessary to ensure that the connection part is firm and reliable, and to ensure that the bus branch is in a position that is not impressed by mechanical equipment, so as to ensure the safety of the DCS communication line.

03 Address identification failure

When the address identification of in-place components and bus interfaces is incorrect, the entire communication network is thrown into chaos. Accidents such as malfunctions in downloads and updates, confusion in address symbols, unaddressable data, and shutdown accidents can occur. In addition, the change of human error address identifier can also lead to packet loss, which can have a devastating impact on the DCS communication system.

Therefore, it is necessary to shut down the system in advance and refresh the configuration data in time before modifying the components.

04 UCN cable fault

The data reading between the controller and the field measuring instrument, as well as the execution of data transmission, is done via a UCN cable. Once the UCN cable alarms and the faulty cable cannot be repaired in time, resulting in the failure of two or more UCN cables, it will have a serious impact on the entire production process, and may cause other chain reactions and cause serious production accidents.

Therefore, it is necessary to pay attention to the protection and routine maintenance of UCN cables, and to prevent such failures with our own technical strength without additional budget. In this regard, isolation measures such as isolation nets and protective covers can be installed around the UCN cable, which can effectively reduce the probability of UCN cable failure. Removing the external influencing factors of the computer room can ensure the stable operation of the DCS communication system and ensure the normal operation of the production equipment.

05 Remote station communication failure

Due to the structural characteristics of the redundant communication of the remote station of the system, under normal circumstances, the main communication card of the electronic room is in the state of continuous green light, and the red light is also always on; The standby communication card is only a solid green light, and there is no red light to warn, etc., and the operator cannot operate the above equipment or change the component parameters during this period, otherwise it will lead to tripping and shutdown.

In the operation of the plant, the risk of replacing the terminal plate is relatively high. Because the installation position of the terminal board is generally poor, but it is relatively necessary to pay attention to the power supply of the terminal board and the power supply of other card terminal boards are connected in series mode, before replacement, it must be ensured that the power supply circuit is in a closed-loop state, if the closed loop is not formed, the wire must be increased to form a closed-loop loop, otherwise when the terminal board is replaced, it will cause the terminal board of some other card parts to be de-energized, causing unnecessary consequences.

Hollysys DCS - DCS common communication faults and solutions

Hollysys DCS - DCS common communication faults and solutions

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