Clause 10.4 is used alongside Dielectric Properties (Clause 10.9) to provide insulation co-ordination within the assembly.
The clearances and creepage distances from phase to phase, phase to neutral, phase to earth and neutral to earth are measured and these distances determine the Uimp and Ui of the assembly.
Clearance is the shortest distance between two conductive parts measured through air. The minimum clearance distance measured on an assembly will determine the rated Uimp as per Table 1.
E.g. For a rating of Uimp 8kV, the minimum clearance must be 8mm.
Creepage is the shortest distance between two conductive parts measured along a surface. The minimum creepage distance measured on an assembly will determine the Ui as per Table 2.
E.g. For a rating of Ui 800V, the minimum creepage must be 12.5mm*.
The assembly must meet the criteria of Tables 1 & 2 to achieve the rated voltages applied during dielectric testing.
Guidance on Clearance & Creepage can be found in Clause 8.3 and Annex F.
* Material group IIIa is applied unless there is documentation of a higher material group, allowing a reduced creepage distance.