2. The expansion effect of different metals varies. The metal expansion coefficient of steel bolts is much smaller than that of copper and aluminum busbars, especially for bolted equipment joints. During operation, with changes in load current and temperature, the degree of expansion and contraction of aluminum or copper and iron will differ, resulting in creep. That is, the metal slowly undergoes plastic deformation under stress, and the creep process is also closely related to the temperature at the joint.

3. Improper pressure on the fastening bolts at the connection point. Some installation or maintenance personnel believe that tightening the connecting bolts on the conductor connection is better, but this is not the case. Especially for aluminum busbars, the elastic coefficient is small. When the pressure of the nut reaches a critical pressure value, if the material's strength is poor and improper pressure is further increased, it will cause deformation and bulging of the contact surface, which will reduce the contact area and increase the contact resistance, thereby affecting the contact effect of the conductor.

4. The conductivity of the selected conductor material does not meet the requirements, mostly due to insufficient purity of the conductor raw material.

5. Other factors on site, such as improper installation and maintenance processes, such as inadequate, uneven, and non smooth treatment of the contact surface of the busbar during processing, connection, and installation, resulting in a decrease in effective contact area, an increase in contact resistance, and heating.

Due to the high temperature inside the switchgear, it can cause insulation breakdown accidents and affect the lifespan of the switchgear equipment. Therefore, special attention should be paid to the temperature changes inside the switchgear during installation and operation.