IEC TS 62271-304:2019 applies to indoor enclosed switchgear and controlgear complying with IEC 62271-200 and IEC 62271-201, intended to be used in special service conditions with respect to condensation and pollution deviating from the normal service conditions specified in IEC 62271-1.


The test detailed in this document has been designed primarily to classify the electrical insulation performance of equipment having high-voltage electrical insulation exposed to indoor service conditions, mainly in presence of condensation. The assessment of mechanical components, such as mechanisms, interlocks and enclosure is also considered.
This second edition cancels and replaces the first edition published in 2008. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous edition:

a) the description of the several service conditions under condensation and pollution;

b) the classification of enclosed switchgear and controlgear, according to the testing procedure does not cover polluted service conditions PL and PH;

c) a wider description in Annex B of typical indoor environments based on ISO/IEC standards;

d) a new Annex C giving guidance on precautions to improve indoor operating conditions;

e) a new Annex D dedicated to the optional items such as records of mechanical characteristics;

f) a new Annex E, giving additional combinations of environments with condensation and pollution, as well as a proposal of testing procedure of ageing test, is provided to create experience on correlation between ageing effects in laboratory and ageing effects at site conditions.