When the fuse in the circuit is fused, when the voltage and current reach a certain value, the fuse link will just melt and break, and there will be a pull arc between the fuse links just separated, which is called arc. It is because the electric field is too strong and the gas is ionized, so that the current passes through the normally insulating medium. The use of electric arc can be used for many purposes, such as electric welding, electric arc furnace in steel making plant, etc. However, if the arc is generated under uncontrolled state, it will cause damage to transmission, distribution and electronic equipment.
The existence of arc prolongs the time of switching apparatus breaking fault circuit and increases the probability of power system short circuit; The high temperature generated by the arc will melt and evaporate the contact surface and burn the insulation material. It may also cause fire, explosion and other hazards to oil-filled electrical equipment; Because the arc can move under the action of electric power and heat, it is easy to cause arcing short circuit and personal injury, resulting in the expansion of the accident. So we must understand and control the arc.