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HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING. Polyolefins are replacing PVC as MV cables sheaths due to: Better mechanical characteristics (abrasion and tear resistance) Lower permeability to moisture No halogens, plasticisers and heavy metals Similar cost.
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HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING • Polyolefins are replacing PVC as MV cables sheaths due to: • Better mechanical characteristics (abrasion and tear resistance) • Lower permeability to moisture • No halogens, plasticisers and heavy metals • Similar cost
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGCost of sheathing materials
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGThe effect of fire in MV cables • MV cables are often installed in enclosed places that can be classified as “key fire-sensitive cable installations”. • A rapid spreading of the fire can take place due to the high working temperature of the cables. • Two main dangers to be considered in a fire: • Explosive growth of the fire • Smoke emission (black and toxic gases)
The maximum heat emission peak for PE is several times higher compared with PVC or HFFR sheathing materials. TPO is a HFFR compound with mechanical and moisture barrier properties similar to those of PE HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGCone calorimeter results for sheathing materials
PVC has a total smoke production higher that any other sheathing material HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGCone calorimeter results for sheathing materials
The fire resistance test of IEC 60332-1-2 can be passed with a HFFR sheathing material (TPO) that exceeds the characteristics of ST-7 of IEC 60502 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGFire resistance test levels
If a fire resistance level in accordance with IEC 60332-3-22 is demanded, the physical properties of the sheathing compound (TPR) are lower HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGFire resistance test levels
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGSheathing materials properties
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGConclusions • Polyolefines present important advantages as sheathing materials for MV cables when compared with PVC. • Polyolefines favour the spreading of fire due to their high ease of inflammation. • It is possible to compound polyolefines to improve the fire resistance. • It is important to adjust the level of fire resistance to the minimum needed in order to improve the physical characteristics of the material and his cost