What Is Creepage Distance and Why Does It Matter?
Quick answer — Creepage distance is the shortest distance along the surface of an insulator (bushing) between the live and earthed ends; it is specified in mm per kV by the pollution class so an external flashover does not occur in a contaminated or wet environment. A higher pollution class (heavier contamination) needs a longer creepage path on the bushing or insulator.
What is creepage distance and pollution class?
What it is
The path along the insulator surface from the live conductor to earth. In contaminated or salt/industrial conditions, a flashover can develop along this surface if the creepage is too short.
Pollution classes
The site protects against this by selecting a pollution class (e.g. light, medium, heavy, very heavy), which sets the creepage distance per kV (e.g. 20 mm/kV for heavy pollution).
Why it matters
It prevents a flashover that would trip the unit, damage the bushing, and disrupt supply. Selecting the right creepage and the right bushing (or profile) is part of the specification.
References & standards
- IEC 60815 (selection of insulators)
- IEC 60137 (bushings)
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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