Comparing high-voltage cables and low-voltage cables, the components from the inside to the outside include: conductor, insulation, inner sheath, filler (armor), and outer insulation. It is mainly used to transmit electric energy, and is often used in the control circuit of fire equipment, the signal of automatic fire alarm system, and the function of system transmission line.
According to the regulations, some high-voltage AC power transmission adopts a three-phase three-wire system, and the three wires are three-phase power from the step-up transformer. illumination.
The lighting circuit also needs a zero line, which is obtained by star connection when the user terminal is stepped down. That is, the three-phase high-voltage electricity is connected to the head of the three-phase transformer winding, and the three tails are connected together to form a zero line. my country's 10KV, 110KV, 220KV. 500KV high-voltage transmission lines have no neutral line, because these voltage levels cannot be directly used for equipment. When the voltage level is above 10kV, the neutral line and the live line together form a phase voltage, and at the same time act as the neutral grounding (working grounding) of the operating equipment. .
However, when the voltage exceeds 35KV, most of the single-core cables are used. The relationship between its core and the metal shielding layer can be regarded as the relationship between the coil and the iron core in the primary winding of a transformer. When the single-core cable core passes current, it will There are magnetic lines of cross-linked aluminum cladding and metal shielding layer to make induced voltage appear at both ends. Single-core cables have the irreplaceable advantages of other cables, and they can withstand higher voltages.
