In this section:

The fundamental reason behind insulation is to protect user against electric shock and energy hazard. Electrical insulation shall be achieved by using...

• solid/laminated insulating material having adequate thickness and adquate creepage distance over their surface. 
• adequate clearance through air. 
• or both. 

OPERATIONAL INSULATION: Insulation needed for the correct operation of the equipment 

BASIC INSULATION: Insulation to provide basic protection against electric shock. 

SUPPLEMENTARY INSULATION: Independent insulation applied in addition to basic insulation in order to ensure protection against electric shock in the event of a failure of the basic insulation. 

DOUBLE INSULATION: Insulation comprising both basic insulation and supplementary insulation. 

REINFORCED INSULATIOIN: A single insulation system which provides a degree of protection against electric shock equivalent to double insulation.