Electric tools are divided into three categories according to the mode of electrical protection:

Class I tools:

I.e. ordinary electric tools with rated voltage exceeding 50V.

A class of electric tools not only rely on the basic insulation but also include an additional safety precautions in the protection against electric shock. The method is to connect the accessible conductive parts with the protective wires installed in the fixed line, so that the accessible conductive parts will not become electrified in the event of basic insulation damage.

For tools equipped with non reconnectable power plugs, the grounding terminal in the tool must be connected with the core wire for protective grounding in the flexible cable or cord.

Class II tools:

That is, the rated voltage of electric tools with double insulation structure exceeds 50V. Double insulation structure is a form of double insulation or reinforced insulation or a combination of both.

In addition to the basic insulation, the double insulation has an independent additional insulation. When the basic insulation is damaged, the operator is separated from the charged body by the additional insulation without electric shock.

The reinforced insulation is to strengthen and improve the basic insulation performance, so that it has the same dielectric strength and mechanical strength as the double insulation, and thus has a considerable safety protection efficiency.

Three types of tools:

That is, the rated voltage of the safe voltage tool is not more than 50V. The protection against electric shock depends on the power supply by the safe voltage and the inside of the tool, and the voltage higher than the safe voltage will not be generated.

The electric shock protection of the three types of tools adopts reliable basic insulation, the insulation of the power supply to the ground and the so-called "triple protection" of extra low voltage below 50V, so that the tools have high safety performance.