Determination of the minimum clearance and minimum creepage distance for electronic equipment in safety examinations;

The determination method of electrical clearance and creepage distance is expounded, and the testing and demonstration method is described.

Calculation and numerical analysis from programming educesaccurate measurement of creepage distance in complicated structure, thereby strengthening the proficiency test ability.

On the basis of the insulation operation experiences and present status of ±500 kV DC overhead lines at home and abroad,and the latest ±800 kV insulators\' withstand voltage test results,we combined a specific leakage distance method and pollution withstand voltage method to get basic insulation selections in ±800 kV line.

The results of analysis on pollution flashover accidents occurred in 500kV transmission lines of East China Power Grid show that insufficient creepage distance and irrational shed profiles of insulators are the principal reasons to cause pollution flashover of transmission lines.

Contamination accumulation characteristics and creepage distance utilization coefficients greatly impact the external insulation characteristics, so these factors should be considered in external insulation configuration.