When the wire continuously passes the maximum allowable load current, the wire is allowed to heat no more than the temperature allowed by the wire core.
The section of low voltage overhead line conductors is generally selected according to the following conditions:
1 According to the allowable current value of the wire selection: When the wire continuously passes the maximum allowable load current, the wire heat does not exceed the allowable temperature of the wire core.
2 Press the allowable voltage loss selection: The voltage loss generated when the conductor continuously passes the normal maximum load current cannot exceed the allow able range to ensure the normal operation of the electrical equipment. The “National Electricity Supply Rules” stipulates that the voltage variation range of low-voltage power users is ±7% of the rated voltage, and that of low-voltage lighting users is +5% to -10% of the specified voltage.
3 Select according to mechanical strength: The wire should be prevented from being installed or operated. For low-voltage overhead line conductor cross-section, aluminum stranded wire is required to be not less than 25mm2, steel-cored aluminum stranded wire is not less than 25mm2, and copper wire diameter is not less than 4mm. When selecting a larger conductor cross-section, consideration should also be given to choosing according to the economical current density to reduce the power loss and operating costs of the circuit.