Can anyone explain the term “Min groove width” located in the “IEC 60664” tab of Calculator Tools->Power, current and isolation->Electrical Spacing? I understand the clearance and creepage parameters calculated on this page but “Min groove width” does not seem to be documented in the Kicad documentation and Google has not helped elucidate an answer.
Found it:
4.6.3 Conditions of conductive pollution
The dimensions for creepage distance cannot be specified where permanently conductive pollution is present (pollution degree 4). For temporarily conductive pollution (pollution degree 3), the surface of the insulation may be designed to avoid a continuous path of conductive pollution, e.g. by means of ribs and grooves (see 5.2.2.5 and 5.2.5).
Perhaps you are too young to be familiar with the popular definition of “groovy.” 
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