Industrial site interference problems and treatment methods
Aluminum Profile Radiator,Aluminum Extrusion Radiator,Industrial Aluminum Radiator,Aluminum Alloy Tube Alinex(Jiangsu) Metal Co.,Ltd , https://www.aluminum-pipe.com
August 10 09:04:25, 2022
At present, various interferences exist in various industrial sites, so the reliability of instruments and control systems directly affects the safe and stable operation of modern industrial production equipment. The anti-interference ability of the system is the key to the reliable operation of the whole system. With the application of DCS and fieldbus technology, the controlled object and the signal to be measured are often distributed in different places, and they also have a long distance from the control station. Therefore, both the signal line and the control line may be long lines. Secondly, there are often many strong electrical equipment on site, and their start-up and work will have a strong impact on the measurement and control system. At the same time, problems such as radiation interference from space and interference from external leads of the system are particularly prominent. Therefore, in addition to the useful signal, there are some currents or voltages that are unrelated to the signal under test for various reasons. This extraneous current or voltage is commonly referred to as "interference (noise)." In the measurement process, if the interference is not handled well, it will distort the measurement results and even make the meter or computer completely inoperable. A large number of practices have shown that anti-interference performance is a very important issue for various electronic measuring devices. Especially the wide application and rapid development of DCS and fieldbus technology, effectively eliminating and suppressing various interferences has become a necessity to explore and solve. Urgent problem, because interference can not only cause logic confusion, system measurement and control failure, resulting in lower product quality, and even damage to production equipment, resulting in accidents. Therefore, the anti-jamming technology must pay sufficient attention in the design, manufacture, installation and daily maintenance of the instrument measurement and control system.
Common sources of interference and interference with the system:
Because the measurement and control signals are often a weak DC or slow-changing radiation interference from space, the impact on the measurement and control system mainly through two paths: one is directly radiated to the computer, and the interference is caused by the circuit; the second is the computer peripherals and The radiation of the communication network is induced by the induction of peripheral devices and communication lines.
There are two main ways of interference from transmission: one is through the power supply of the sensor power supply or the common signal instrument, that is, the power supply that the distributor is connected to; the second is that the signal line is interfered by the space electromagnetic radiation, and the component is damaged in severe cases. , logic errors and large system failures.
The interference from the grounding system is mainly caused by the grounding system chaos: the noise coupling interference caused by the shielding grounding wire of the measurement and control system and the grounding wire of the casing, the signal grounding wire, the power grounding wire, and the AC power grounding wire.
In summary, we can summarize the interference current (voltage) generated by various interference sources (noise sources) to the measuring device and the detection system. It needs to have three elements at the same time: (1) noise source; (2) noise-sensitive receiving circuit; (3) The path from the noise source to the receiving circuit.
Universal anti-jamming technology:
Since the formation of noise interference to the measuring device and the detection system requires "three elements", the method of eliminating and attenuating the noise interference should also take measures against three factors, namely: (1) eliminating or suppressing the noise source; (2) blocking the interference transmission path; (3) Impair the sensitivity of the receiving circuit to noise interference. The above three measures are all hardware measures. With the application of microcomputers in industrial production, smart sensors and smart meters, in terms of software, more measures and methods to suppress interference such as digital filtering and digital processing have been applied, and the safety level of instrument monitoring and control systems has been greatly improved. The above several measures are usually completed by isolation, shielding, suppression, grounding protection, and software technology. The following technologies are introduced one by one.
Isolation contains two meanings: one is reliable insulation, that is, it does not cause leakage current between the wires, so the voltage resistance level and insulation resistance of the wire insulation material must meet the requirements; the other is reasonable wiring, that is, the signal line is required Avoid interference sources. For example, when the power line and the signal line are laid in parallel, the two must be kept at a certain distance. When the two are crossed, they should be as perpendicular as possible. When the wires are laid, the power and signal lines should be in different conduits. Signal lines with different signal amplitudes should not be worn in the same conduit. When using metal wire troughs, different spoke wires, cables and power lines need to be separated by metal partitions. Signal lines with different amplitudes should not be used in the same multi-core cable.
Shielding and suppression are surrounded by shielded components, assemblies, circuits and signal lines with metal conductors. They are mainly used to suppress current noise and combine to provide a certain magnetic shielding effect. In addition, the use of twisted pairs instead of two parallel lines is an effective way to suppress magnetic field interference.
Grounding protection means protecting equipment and personal safety and suppressing interference through grounding. It is usually divided into shielded grounding, intrinsically safe grounding, protective grounding, and signal loop grounding. The following are introduced respectively: (1) Protective grounding is a good metal connection between the metal parts of the electrical equipment and the power meter that are normally not energized and the grounding body. If the instrument panel is accidentally charged, the grounding short-circuit current mostly passes through the grounding resistance; (2) The working grounding ensures that the meter works accurately and reliably. It includes signal loop grounding, shield grounding and intrinsically safe instrument grounding.
Software anti-interference technology: The complex environment of the industrial site hardware anti-interference measures can not do anything, such as the industrial computer crash or control error. This will have dire consequences for production, so it is important to use software anti-jamming measures to avoid and mitigate these accidents. The commonly used software anti-jamming technologies are: self-monitoring method in real-time control software operation, mutual monitoring method of real-time control system and important data backup method.