1. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 1 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

2. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 2 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Cost of sheathing materials

3. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 3 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING The 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)

4. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 4 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Cone calorimeter results for sheathing materials 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

5. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 5 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Cone calorimeter results for sheathing materials PVC has a total smoke production higher that any other sheathing material

6. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 6 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Fire resistance test levels 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

7. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 7 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Fire 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

8. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 8 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Sheathing materials properties PropertiesUnitsMaterialsTest Method TPOTPR Tensile strengthN/mm²>12.5>10EN 60811-1-1 Elongation at break%300125EN 60811-1-1 Tear resistanceN/mm>20>8ISO 34.1 Abrasion resistance on cable -PassNot passHD-605.2.4.22 Oxygen index->27>32ISO 4589 Acid gas test Conductivity Ph Halogen content µS.cm -1 % <10 >4.3 <0.5 <10 >4.3 >0.5 EN 50267-2-3 EN 50267-2-1

9. ROVIRA-SP-ALPHA1-BLOCK2 Barcelona 12-15 May 2003 9 HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING Conclusions 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