Are there any restrictions on the material of cable conduit tubes?
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Are there any regulations regarding the material of cable conduit? Metal wire conduits are commonly used. Recently, in areas where corrosion was severe, our electrical engineers opted for PVC wire conduits, and the results have been good. So, can non-metallic wire conduits be used in areas where external impacts are unlikely to occur? Are there any specification requirements for the material of cable conduit?
Yes, according to the Design Code for Power Engineering Cables GB 50217–2007, section 5.4 on the installation of protective pipes, sub-section 5.4.1 states that the inner surface of the cable protective pipes should be smooth and free of burrs. Its selection shall meet the mechanical strength and durability required by the operating conditions, and shall comply with the following provisions: 1 When it is necessary to use conduit to suppress electrical interference to the control cables, steel conduit shall be used. 2 When a single-core communication cable is run in a conduit individually, steel conduits with unseparated magnetic paths shall not be used. 5.4.2 The selection of cable protection pipes that are partially or fully exposed to air shall comply with the following requirements: 1 In areas with high fire or mechanical protection requirements, steel pipes should be used. Anticorrosion treatments suitable for environmental durability requirements, such as painting or galvanizing with plastic coating, should also be applied. 2 When the self-extinguishing requirements of engineering conditions are met, flame-retardant plastic pipes can be used. In applications where it is partially embedded in concrete and subject to impact, plastic pipes should have the appropriate pressure resistance, and flexible plastic pipes are preferred. There is also the issue of fire protection cables; the Building Code “recommends” the use of metal conduits.
Fire protection conduits that are installed openly must be metal conduits.
“2 When a single-core communication cable is run in a conduit individually, steel conduits with unseparated magnetic paths shall not be used. ”I don’t understand what it means. Could you please explain it? Thank you!
When a single-core communication cable is passed through a conduit individually, if ordinary steel pipes are used, their strong magnetic conductivity leads to the generation of eddy currents that cause heating, thereby reducing the cable’s current-carrying capacity. To avoid this issue, it is necessary to divide the steel pipe into sections that do not form a continuous magnetic path; however, I have not seen any specific methods for doing this. It seems that a section of non-magnetic material should be added along the portions of the pipe that are parallel to the straight sections.
Why is this the case for single-core ones? Does \"single core\" refer to a single strand of wire? What about multi-conductor cables? I’m an amateur with no knowledge of basic electrical principles; please don’t laugh at me :L
Multi-core cables, such as three-phase cables together, have a vector sum of the three-phase currents equal to 0, and the magnetic fluxes generated are also canceled out – that’s my guess
Or one fire and ten also cancel each other out. In reality, there aren’t any wires that pass through a conduit with just one wire; at least it should be a 2-core wire
I think the same way; I just don’t know if it’s correct
There are single-core high-voltage cables available in 10 kV, 35 kV, 66 kV, and 110 kV ratings; these cables consist of multiple copper conductors that make up one cable core, and can be used only as single-phase power cables.