Rated voltage of 1kV and lower voltage power line. Low-voltage lines, including low-voltage overhead lines, low-voltage overhead insulated lines, low-voltage cable lines and indoor distribution lines for the direct transmission of low-voltage electrical equipment is an important part of the low-voltage distribution system (see LV distribution). Low-voltage lines can access from the public low-voltage distribution network, through the low-voltage distribution room leads; also by the user-owned low-voltage power distribution room leads to the distribution unit.
When the wire continuously passes the maximum allowable load current, the wire does not heat up beyond the allowable temperature of the core.
Low-voltage overhead line conductor cross-section according to the following general conditions of choice:
① According to the allowable current value of the conductor selection: When the conductor continuously through the maximum allowable load current, so that the wire does not exceed the core allows the heating temperature.
② According to the allowable voltage loss option: The voltage loss generated when the wire passes the normal maximum load current can not exceed the allowable range, so as to ensure the normal operation of the electrical equipment. The "National Rules for the supply of electricity," provides: low voltage power user voltage range of ± 7% of rated voltage, low voltage lighting users are the provisions of voltage +5% ~ -10%.
③ according to the mechanical strength of choice: should prevent wire in the installation or operation of the break line. Low-voltage overhead line conductor cross-section, the required aluminum strand is not less than 25mm2, ACSR not less than 25mm2, copper wire diameter of not less than 4mm. Select a larger wire cross section, should also consider the economic current density to choose, in order to reduce the power loss and operating costs of the line.