The phenomenon of heating of wire joints is generally first manifested as a peculiar smell around the wire joints, which can be smelled. This is caused by the heating of the wire joints to cause the outer insulation layer to produce odor; secondly, smoke, redness and blackening of the outer insulation layer at the wire joints , Catch fire, or even disconnect. The heating of wire joints will not only cause a large amount of power loss, but also seriously affect the normal operation of electrical equipment. In the light of the increase in working current in the line, the life of electrical equipment will be shortened, and in the worst case, the ongoing production, scientific research, and medical treatment will be suddenly interrupted. Surgery and other activities can also lead to fires and electric shocks, causing incalculable losses.

When laying wires, some electrical installation workers often do not pay attention to the installation quality: no casing is installed where insulation sleeves should be used; junction boxes are not installed where junction boxes should be used; even splicing is not used at wire joints , But the illegal hook connection method. The contact resistance of this hook-like connection method is very large, and the continuous heating when energized will gradually dry and char the nearby wooden boards, and then burn and cause a fire.