Insulation coordination for equipment within low-voltage systems - Part 5: Comprehensive method for determining clearances and creepage distances equal to or less than 2mm
1 Scope and Object
This part of GB/T 16935 specifies the dimensioning of clearances and creepage distances for spacings equal to or less than 2 mm for printed wiring board and equivalent constructions, where the clearance and the creepage distance are identical and are along the surface of solidinsulation, such as the paths described in 6.2 of Part 1 (Examples 1, 5 and 11).
The dimensioning in this standard is more precise than that provided by Part 1. However, if the precision provided by this standard is not required, Part 1 may be applied instead.
This part can only be used in its entirety. It is not permitted to select one or more clauses from this part and to use them in place of the corresponding clauses of Part 1. In addition, this part can only be used together with Part 1.
When this part is applied to the dimensioning of electric clearances and creepage distances, all clauses shall be used in place of the corresponding clauses given in Part 1. For clearances and creepage distances larger than 2 mm, and for solid insulation in general, Part 1 applies.
NOTE 1 The limitation to distances equal to or less than 2 mm applies to basic or supplementary insulation. The total distance of a reinforced or double insulation may be larger than 2 mm.
This part is based on the following criteria for dimensioning:
——minimum clearances independent of the micro-environment (see Table 2);
——minimum creepage distances for pollution degrees 1, 2 and 3 to avoid failure due to tracking (see Table 4);
——minimum creepage distances to avoid flashover across the insulating surface (see Table 5).
Foreword i
Introduction ii
1 Scope and Object
2 Normative References
3 Terms and Definitions
4 Fundamentals of Clearance and Creepage Distance Dimensioning
4.1 Introductory Remark
4.2 Basic Principles
4.3 Voltages and Voltage Ratings
4.4 Frequency
4.5 Time under Voltage Stress
4.6 Pollution
4.7 Information Supplied With the Equipment
4.8 Insulating Material
5 Requirements and Dimensioning Procedures
5.1 General
5.2 Dimensioning of Clearances
5.3 Dimensioning of Creepage Distances
5.4 Requirements for Design of Solid Insulation
6 Tests and Measurements
6.1 Tests
6.2 Measurement of Creepage Distances and Clearances
Annex A (Informative) Dimensioning to Maintain Minimum Insulation Resistance
Annex B (Normative) Water Adsorption Test
Annex C (Informative) Dimensioning Diagrams
Annex D (Informative) Withstand Voltage Test for Creepage Distance under Humid Conditions
Bibliography
