creepageclearance

Creepage clearance is a fundamental concept in electrical insulation coordination, referring to the minimum distances that must be maintained between conductive parts to prevent electrical breakdown, arcing, or surface tracking. The topic is commonly discussed in terms of two related measurements: creepage distance and clearance distance. Creepage distance is the path along the surface of an insulating material between two conductors or between a conductor and grounded surface. Clearance distance is the straight-line distance through air (or another insulating medium) between the same two conductors. Both distances contribute to safe operation and are specified to withstand operating voltages and environmental conditions.

Standards and methodology: Safety standards provide a structured approach to determine required creepage and clearance values. IEC 60664-1, for example, outlines how to select these distances based on system voltage, pollution degree, and insulation material group. The figures appear in published tables and may be adjusted by design margins for transient surges, humidity, and contamination. Other standards for equipment safety and electrical installations may reference these values or provide supplementary rules for specific applications.

Factors and application: Required distances depend on working or peak voltage, the insulation material group (material class), pollution degree of the environment, and altitude. Higher pollution or conductive contamination typically necessitates longer creepage distances. Applications include power supplies, enclosures, printed circuit boards, transformers, and high-voltage equipment. Designers ensure track spacings, terminal clearances, and surface distances comply with the specified creepage and clearance values.

Measurement: Creepage is measured along the surface of insulation; clearance is the shortest path through air. Both are expressed in millimeters and influence component layout, PCB design, and enclosure isolation.