Hollow Insulators pollution performance

Hollow Insulators pollution performance depends on the pollution levels, creepage distance, and shed design. Guidance on design and selection of creepage distance with respect to conditions are as per IEC 60815.

Hollow Insulators

Hollow Insulators pollution performance:
Pollution levels:
Guidance on design and selection of creepage distance with respect to environmental conditions can be found in IEC recommendation 60815.
Basic levels of pollution are qualitatively defined with examples of typical environment situations.
Corresponding minimum nominal creepage distance is given in mm/kV.

Level 1: light pollution, 16mm/KV & 0.630 inch/KV specific creepage distance
Areas without industry and with low housing density equipped with heating plants.
Areas with low density of industry or houses but subjected to frequent winds and/or rainfall.
Agricultural areas.
Mountainous areas.

Level 2: medium pollution, 20 mm/KV & 0.787 inch/KV specific creepage distance
Industrial areas not producing particulate polluting smoke and/or with average housing density equipped with heating plants.
Areas with high density of houses and/or industry but subjected to frequent winds and/or rainfall.
Areas exposed to wind from the sea but not too close to the coast (at least several kilometers distant).

Level 3: heavy pollution, 25 mm/KV & 0.984 inch/KV specific creepage distance
Areas with high density of industries and suburbs of large cities with high density of heating plants producing pollution.
Areas close to the sea in any case exposed to relatively strong winds from the sea.

Level 4: heavy pollution, 31 mm/KV & 1.220 inch/KV specific creepage distance
Areas generally of moderate extent, subjected to conductive dusts and to industrial smoke producing particularly thick conductive deposits.
Areas generally of moderate extent, very close to the coast and exposed to sea-spray or to very strong and polluting winds from the sea.
Desert areas, characterized by no rain for long periods, exposed to strong winds carrying sand and salt, and subjected to regular condensation.

The creepage distance should be increased in relation to the average diameter, Dm.

Shed design:
The plain alternative shed design offers high specific creepage distance together with good self-cleaning properties and usually provides best performance. Using flexible shed design can optimize most insulators.
Alternating shed, plain shed, standard (traditional) shed, under rib shed

Parameters Characterizing Insulator Profile:
Minimum distance, c, between sheds
Generally c ≥ 30 mm.
For small insulators (H < 550 mm) or overhang (p ≤ 40 mm), c can be ≥ 20 mm.
Ratio s/p between spacing and overhang
Sheds without under ribs ≥ 0.65
Sheds with under ribs ≥ 0.8.
Ratio ld/d between creepage distance and clearance
This ratio must be calculated for the“worst case” on any section (ld1/d1, ld2/d2).
It must be < 5.
Alternating shed
p1- p2≥ 15 mm

Parameters Characterizing Entire Insulator
Creepage factor C.F.
C.F. ≤ 3.5 for pollution levels 1 and 2.
C.F. ≤ 4 for pollution levels 3 and 4.
Profile factor P.F.
P.F. > 0.8 for pollution levels 1 and 2.
C.F. > 0.7 for pollution levels 3 and 4.


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