What is the creepage distance and protected creepage distance of insulator?

Creepage distance and protected creepage distance are main parameters for electrical insulator, especially creepage distance of insulator.

What is the creepage distance of insulator?

Creepage distance of insulator, also called the leakage distance, is the shortest distance between two conductive parts measured along the insulator surface. You can say that it is the creep path length of electric conducting department from the top of the insulator to the bottom of the metal department along the insulator surface, or the shortest distance of outer surface of the insulator insulation end to the other end.

The total creepage distance of an insulator shall be not less creepage distance requested by the pollution level for the site.

What is the protected creepage distance of an insulator?

Protected creepage distance of an insulator means part of the creepage distance on the illuminated side of the insulator which would lie in shadow if light were projected on to the insulator at 90°(or 45°in special cases) to the longitudinal axis of the insulator.

The creepage distance and protected creepage distance of insulator is common technical terms; we should know this knowledge before designing, manufacturing insulators.