Single core means that there is only one conductor in an insulation layer. When the voltage exceeds 35kV, most single-core cables are used. The relationship between the core and the metal shield can be regarded as the relationship between the coil and the iron core in the primary winding of a transformer. When a single-core cable core passes an electric current, there will be a magnetic wire cross-linked aluminum package or a metal shielding layer, so that an induced voltage appears at both ends thereof.
35kV and below voltage cables are grounded at both ends. This is because most of these cables are three-core cables . In normal operation, the sum of the currents flowing through the three cores is zero. The aluminum package or metal shield There is basically no magnetic link outside. In this way, there is basically no induced voltage at the two ends of the aluminum bag or metal shield, so no induced current will flow through the aluminum bag or metal shield after the two ends are grounded.
Power cables generally consist of single-core, double-core, and triple-core cables consisting of wires, insulation, and protective layers.
Single core means that there is only one conductor in one insulation layer. If it is to be used in a single-phase lighting circuit, two wires need to be laid in parallel. Double-core means that there are two conductors in one insulation layer. If it is to be used in single-phase lighting circuits, only one is laid. (Wires are divided into multiple strands and single strands, and are divided into soft cores and hard cores. Selection according to the conditions of use and power)