Questions and answers on common shielding wiring systems such as lightning protection, grounding and safety
Q: Is it dangerous to use shielding system?
Answer: No. If TN-S system is adopted, the system is as safe as unshielded twisted pair system. Poor grounding or distribution system will affect various copper cable wiring systems. If TNC or TN-C system is adopted. Current will appear on PE (N) line. If it is a shielding system, current will appear on the shielding layer and the reference potential. If an unshielded twisted pair system is used, a current will appear at the reference potential. When lightning strikes, the damage risk of shielding system is much lower than that of unshielded twisted pair system.
Q: I have a TN-C or TN-C-S system. How do I use the cabling system?
Answer: First, measure the current on the PE in the power distribution system. If the potential difference is higher than 1V, equipotential lines shall be installed between distribution points. A more effective way is to change the distribution system. In both cases, PEN cable will cause many problems.
Q: Should the shielding layer be connected at one end or at both ends?
Answer: It should always be connected at both ends (that is, on the distribution frame and network equipment, not on the socket), so as to effectively suppress all electromagnetic compatibility mechanisms and avoid antenna effects.
Q: Is it necessary to use metal barriers in the cable ducts of the shielding system?
Answer: It is only required when the pipe length is more than 35 meters. For the unshielded twisted pair system, metal diaphragms must always be used.
Q: Is it enough to use the FTP cable? Is it better to use PiMF cable?
Answer: From the perspective of electromagnetic compatibility and performance, The PiMF cable is the best solution.
Q: Does lightning strike also affect the unshielded twisted pair system?
Answer: Yes. If there is no lightning protection system, the magnetic flux will be very strong, so that the line pair in the unshielded twisted pair cable cannot suppress the signal. Compared with the shielding system, the probability of internal system failure caused by lightning near the structure is 10000 times higher. This is described in IEC62305-2/FDIS.
Q: Can the unshielded twisted pair system meet the EMC requirements?
A: It is possible. There is no EMC standard for cabling systems today. Therefore, from a system perspective, there are no restrictions that must be met. The EMC directive only requires the owner to be responsible for not interfering with other systems and not being interfered by other systems. Some tests show that the unshielded twisted pair system cannot meet the requirements of EN 55022B. This standard is for residential and office environments.
Q: I have an unshielded twisted pair system. Do I need a grounding system?
Answer: Yes. Grounding is for safety. All electrical facilities with voltage exceeding 25V AC, 60VDC or within SELV must be grounded. Even for optical fiber facilities, a well designed full function grounding system is necessary.
Q: I have an unshielded twisted pair system. Do I need an equipotential bonding system?
Answer: Yes. Equipotential bonding is for safety. All electrical facilities must have equipotential bonding. In addition, it can improve the EMC performance. This applies to various cabling systems.
Q: My system supplier has provided an EMC guarantee/compliance guarantee for my wiring system. Does this mean that I have fulfilled my responsibilities?
Answer: No. If the system is active, there is no clear meaning at present.
Q: My unshielded twisted pair system uses twisted wire pairs as protection. Is this efficient enough to suppress interference?
Answer: No. Twisting can reduce interference, but can not effectively eliminate interference. Intertwist cannot restrain electromagnetic radiation. This will be more serious if the cable is stretched or flattened during installation. Because the geometry is no longer uniform.
Q: I have an unshielded twisted pair system and want to improve my EMC performance. What should I am going to do?
Answer: The most effective way is to incorporate cables and components into the shielding environment. This environment can be shielded cable ducts and channels. Shielded racks and distribution frames can provide some basic protection. Note: All components must be connected to the equipotential bonding system.
Q: I have a shielded system and want to use unshielded jumper wires. Is this possible?
Answer: The system can work as if equipped with shielded jumper wire. However, there is no complete connection to the ground (only on the terminal block), so there is no electromagnetic interference suppression capability. Therefore, shielded jumpers should always be used.
Q: What is the difference between grounding and grounding?
Answer: There is no difference, just two words of the same pair.
