a. Functional insulation-only the insulation required for the equipment to complete its normal function.

b. Basic insulation-insulation added to live parts to provide basic protection against electric shock

c. Supplementary insulation-independent insulation applied in addition to basic insulation, used to reduce the risk of electric shock once the basic insulation fails.

d. Double insulation-insulation composed of basic insulation plus additional insulation.

e. Reinforced insulation-a single insulation structure, under the conditions specified in this section, the protection level it provides against electric shock is equivalent to double insulation.