The main reason for the overload is that the wire cross-section is not properly selected,and the actual load has exceeded the safe current of the wire;

There is also the phenomenon of“small horse-drawn carts”,that is,too many high-power equipment is connected to the line,which exceeds the load capacity of the distribution line.

Lighting lines in important material warehouses,residential areas and public buildings,power lines that may cause long-term overload of wires or cables,and insulated wires with ductile jackets when laid on flammable or difficult-to-burn building components Should be overload protection.The overload protection of the line should adopt automatic switch.During operation,the automatic switch long delay action setting current should not be greater than the line long-term allowable load current.If a fuse is used for overload protection,the rated current of the fuse melt shall not be greater than the long-term load current of the line.When the automatic switch is used as the protection device,its current release device should be installed on the phase line in the three-phase four-wire system with neutral grounding;in the three-phase four-wire system with neutral neutral point,It is allowed to be installed on two phases;in the two-phase two-wire system that is not grounded,it is allowed to be installed on one phase.In a communication power system,the function of automatically disconnecting the power supply from the power supply due to excessive load is called overload protection.