www.ti.com

Insulation:

Pollution Degree:

Installation Category:

ISO7220A, ISO7220C, ISO7220M

ISO7221A, ISO7221C, ISO7221M

SLLS755F – JULY 2006 – REVISED AUGUST 2007

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.

19

Submit Documentation Feedback