EVS-EN 60664-5:2008

This part of IEC 60664 specifies humidity levels regarding the effects of humidity on creepage distances.
This part introduces the following dimensioning criteria which need to be taken into account:
–new minimum clearances having more precise values for dimensions up to 2 mm under pollution degrees 2 and 3 than those specified in Table F.2 of Part 1;
–smaller minimum creepage distances for printed wiring boards and equivalent constructions under pollution degree 3 than those specified in Table F.4 of Part 1;
–a specification of minimum creepage distances to avoid flashover of the insulating surfaces, the values being based on the water adsorption characteristics of the material;
–a specification of minimum creepage distances to ensure adequate insulation resistance under humid conditions.
NOTE Table A.2 provides information on the dimensioning of creepage distances in order to maintain adequate insulation resistance for r.m.s. voltages up to 10 000 V, corresponding to creepage distances up to 250 mm.
The information in this standard is based on research data published in 1989 [1, 2] .
The following details from this research provide background information:
–the research was carried out on test samples that were manufactured using the same process as for printed wiring boards with spacing of circuit patterns from 0,16 mm to 6,3 mm;
–ten different materials were used for the test samples. The influence of the manufacturing process on the surface of the material, e.g. moulding or machining, was not part of the research project;
–the test samples were placed in different locations, such as city, rural, industrial, desert, and coastal;
–the samples were periodically exposed to a voltage stress and the data accumulated over a long period of time.
Annex B specifies a water adsorption test method for allocating unclassified insulating material to the relevant water adsorption group. This annex will be reviewed when further experience is gained using the test method for different materials.