Creepage Distance: Determined by Pollution Level
The creepage distance (the leakage path along an insulating surface) for power equipment is determined by the pollution level. The specific creepage distance (mm/kV) increases progressively across pollution levels I through IV, in accordance with standards GB/T 5582 (pollution levels) and IEC 60815; for low-voltage equipment, GB/T 16935 (pollution degrees) applies. Industry experts note that determining these standards involves checking specific parameters: specific creepage distance (leakage distance per unit voltage) is set based on pollution levels (reference values: Class I 16 mm/kV, Class II 20, Class III 25, Class IV 31 mm/kV);
pollution degrees (for low voltage) are selected based on the environment; and creepage distance (to prevent pollution flashover) is designed and verified according to the standards.
Key Standard Points
- Specific creepage distance: Increases with pollution levels (I–IV) to prevent pollution flashover;
a core parameter; - Pollution levels: GB/T 5582 pollution levels (Class I: Clean to Class IV: Heavy Pollution), determined by the environment;
- Low-voltage pollution degrees: GB/T 16935 pollution degrees (1–3), for low-voltage insulation;
- Material properties: Insulation materials (CTI—Comparative Tracking Index), material compatibility;
- Shape factor: Insulator sheds (shape factor), optimization of creepage distance.
Key Takeaways
First, selection based on pollution.
Specific creepage distance is determined by pollution levels (I–IV) to prevent pollution flashover.
Second, material compatibility.
Insulation material CTI (tracking resistance) must be matched to prevent tracking.
Third is the shed design.
This involves the design of insulator sheds (shape and spacing) and the optimization of creepage distance.
Fourth is acceptance verification.
This entails verifying the product upon delivery (including measuring creepage distance) to prevent the use of substandard components.
Pitfalls to Avoid
First is “insufficient creepage distance.”
Inadequate creepage distance in polluted areas leads to pollution flashover;
specific creepage distance must be verified.
Second is “material mismatch.” Low CTI materials lead to tracking and breakdown;
material compatibility is crucial. Third is “poor shed design.”
Poor shed design results in inflated creepage distance figures;
design optimization is required.
Trends and Reminders
Insulation technology is moving toward “high performance,” characterized by trends in composite insulation (pollution resistance) and hydrophobic materials (self-cleaning properties).
Designers are advised to determine specific creepage distance based on pollution levels, ensure material compatibility, and conduct rigorous acceptance verification.
Adhering to creepage distance standards ensures insulation safety and stability.
