The issue of repeated grounding for low-voltage motors in TN-S systems
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The power supply system designed by the design institute is of the three-phase five-wire TN-S type. For the grounding of low-voltage motors on site, the fourth conductor in the cable is used for grounding; no additional grounding is required near the motors. Please discuss whether this complies with relevant standards – I’m not sure which regulations address this issue.
The concept of grounding the fourth conductor in the TN-S system is correct. However, he required that the fourth wire be connected to the three phase live wires on the same contactor. That is, the main circuit uses a four-contact contactor, with the fourth wire closing and opening simultaneously with the three-phase live wires.
I heard about quadrupolar contactors for the first time; I’m not sure if there are any relevant standards or regulations Personally, I think grounding with a fourth cable should be sufficient; it’s more reliable than on-site grounding. The design institute in question is one of the best in the country, so there shouldn’t be any problems
Our company also uses a low-voltage power system with five wires, but we have never used four-pole contactors. Do such contactors really exist? What are its advantages? Could the moderator upstairs give some advice? Thank you!
Reply to 4# Mingri Dongsheng: I also learned about it and understood its meaning from the Internet; you can go to http://bbs.hcbbs.com/viewthread.php?tid=422039 to take a look.
In chemical processing systems, especially in areas equipped with explosion-proof devices, the TN-S power supply system is generally used, and it is required that the ground wire come from the power source side; therefore, redundant grounding is not necessary.