ISO721, ISO721M

ISO722, ISO722M

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SLLS629I – JANUARY 2006 – REVISED FEBRUARY 2010

Insulation:

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:

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.

Installation Category:

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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REVISION HISTORY

Changes from Revision H (June 2009) to Revision I

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Changed 50 kV/s to 50 kV/µs ............................................................................................................................................... 1

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