single-core cable

Single-core cable is a cable with only one conductor in the insulation layer. Single core means that there is only one conductor in one insulating layer. When the voltage exceeds 35kV, most single-core cables are used. The relationship between its wire core and metal shielding layer can be seen as the relationship between the coil and the iron core in the primary winding of a transformer. When the core of a single-core cable passes through the current, there will be a magnetic wire cross-linked aluminum or metal shielding layer, which will cause the induced voltage at both ends.

Regulations for single-core cable

Cables with voltage levels of 35kV and below are grounded at both ends. This is because most of these cables are three-core cables. In normal operation, the total current flowing through the three cores is zero, and there is basically no magnetic link outside the aluminum clad or metal shielding layer. In this way, there is basically no induced voltage at both ends of the aluminum clad or metal shielding layer, so there will be no induced current flowing through the aluminum clad or metal shielding layer after grounding at both ends. Power cables are generally composed of conductors, insulation layer and protective layer, including single-core, double-core and three-core cables. Single-core refers to that there is only one conductor in an insulation layer. If it is to be used in a single-phase lighting circuit, it needs to be laid in two parallel circuits. Double-core means that there are two conductors in one insulating layer, and only one conductor is used for laying in single-phase lighting circuit. (The wire can be divided into multiple strands and single strand, and soft core and hard core. The type selection is based on the use conditions and power)

Specification for fixing single core cables

1. Influence of electrodynamic force In order to prevent the effect of electrodynamic force caused by short circuit, the single-core cable must be of sufficient strength. (1) The support is firmly fixed so that it can withstand the electric force corresponding to the expected short-circuit current. 2. Special precautions for high-voltage AC single-core cables. High-voltage AC lines should use multi-core cables as far as possible. When single-core cables must be used for circuits with large working current, the following precautions should be taken: (1) The cables should be unarmored or armored with non-magnetic materials. In order to avoid circulating current, the metal shield should be grounded at only one point. (2) All conductors in the same circuit shall be placed in the same pipe, conduit or trunking, or all phase conductors shall be installed and fixed together with clamps, unless they are made of non-magnetic materials. (3) When installing two, three or four single-core cables to form single-phase circuit, three-phase circuit or three-phase and neutral circuit respectively, the cables shall contact each other as much as possible. In all cases, the distance between the outer sheath of two adjacent cables shall not be greater than the diameter of one cable. (4) When the single-core cable with rated current greater than 250A must be installed close to the steel cargo bulkhead, the clearance between the cable and the cabin arm should be at least 50mm. Cables belonging to the same AC circuit are laid in trefoil shape, except. (5) Magnetic materials shall not be used between single-core cables of the same group. When cables pass through steel plates, all conductors of the same circuit shall pass through steel plates or stuffing boxes together, so that there is no magnetic material between cables, and the gap between cables and magnetic materials shall not be less than 75mm. Cables belonging to the same AC circuit are laid in trefoil shape, except. (6) In order to make the impedance of three-phase circuit of equivalent length composed of single-core cables with conductor section equal to or greater than 185mm2 approximately equal, each phase shall be transposed once at the gap of not more than 15m. Alternatively, the cable can be laid in a trefoil shape. When the cable laying length is less than 30m, the above measures may not be taken. (7) When several single-core cables are used in parallel in each phase of the line, all cables shall have the same path and equal cross-section. Moreover, cables belonging to the same phase should be laid alternately with cables of other phases as far as possible to avoid uneven distribution of current.