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Insulation:

Pollution Degree:

Installation Category:

ISO721, ISO721M

ISO722, ISO722M

SLLS629B – JANUARY 2006 – REVISED MAY 2006

ISOLATION GLOSSARY (continued)

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 and supplementary insulation.

Reinforced insulation -- A single insulation system which provides a degree of protection against electric shock

equivalent to double insulation.

Pollution Degree 1 -- No pollution, or only dry, nonconductive pollution occurs. The pollution has no influence.

Pollution Degree 2 -- Normally, only nonconductive pollution occurs. However, a temporary conductivity caused

by condensation must be expected.

Pollution Degree 3 -- Conductive pollution occurs or dry nonconductive pollution occurs which becomes

conductive due to condensation which is to be expected.

Pollution Degree 4– Continuous conductivity occurs due to conductive dust, rain, or other wet conditions.

Overvoltage Category -- This section is directed at insulation co-ordination by identifying the transient

overvoltages which may occur, and by assigning 4 different levels as indicated in IEC 60664.

I: Signal Level -- Special equipment or parts of equipment.

II: Local Level -- Portable equipment etc.

III: Distribution Level -- Fixed installation

IV: Primary Supply Level -- Overhead lines, cable systems

Each category should be subject to smaller transients than the category above.

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