What is Creepage and Clearance Distance of Insulator?

What is Creepage and Clearance Distance of Insulator?

In high voltage

transmission line, the leakage current is caused by atmospheric condition such as dirt, pollution, salt and particularly rain water. Finally, these weather condition leads to flashover of the high voltage insulator. So decrease the leakage current this the surface is molded into a series of corrugations or concentric disc shapes. These usually include one or more sheds; downward facing cup-shaped surfaces that act as umbrellas to ensure that the part of the surface leakage path under the ‘cup’ stays dry in wet weather.

What is creepage:

The distance measure of along the surface of the solid insulating material is called creepage distance. The creepage distance is depending upon the weather condition. Minimum creepage distance are 16-25 mm/kV. For high pollution area, these value must be increased.

S No. Degree of Pollution Recommended Creepage Distance for Insulators
1 Clean areas 16 mm/kV
2 Moderately polluted areas 20 mm/kV
3 Industrial areas 22 mm/kV
4 Heavily polluted areas 25 mm/kV +


creepage and clearance distance
creepage and clearance distance

What is clearance:

Distance between two terminal of the high voltage insulator is called clearance distance. Clearance shall be dimensioned to withstand the required impulse withstand voltage, in accordance to table “Clearances to withstand transient overvoltages”.

Ref: https://en.wikipedia.org/wiki/Insulator_(electricity)

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