(5) Magnetic materials(single core cable) shall not be used between single core cables of the same group. When the cable passes through the steel plate, all conductors of the same circuit shall pass through the steel plate or stuffing box together, so that there is no magnetic material between the cables, and the gap between the cable and the magnetic material shall not be less than 75mm. Except for cables with the same AC circuit laid in trefoil shape.
(6) In order to make the impedance of the three-phase circuit(single core cable) with a considerable length composed of single core cables with a conductor section equal to or greater than 185mm2 approximately equal, each phase shall be transposed once at a gap of no 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 necessary.
(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 section. Moreover, cables belonging to the same phase shall be laid alternately with cables of other phases as far as possible to avoid uneven current distribution.