rovira-sp-alpha1-block2 barcelona 12-15 may 2003 1 hffr materials with improved mechanical...
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1ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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
2ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING
Cost of sheathing materials
0
0,5
1
1,5
2
PVC MDPE TPO TPR Material cost in€/l
3ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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)
4ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHINGCone 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
Heat Release Rate , HRR (kW/m2)
0
200
400
600
800
1000
1200
1400
0 2 4 6 8 10Time (minutes)
HR
R (
kW/m
2)
PETPOPVCTPR
5ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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
Smoke Produced Rate, SPR (m2/s)
0
0,02
0,04
0,06
0,08
0,1
0,12
0 2 4 6 8 10
Time (minutes)
SP
R (
m2
/s)
PE
PVC
TPO
TPR
6ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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
7ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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
8ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
HFFR MATERIALS WITH IMPROVED MECHANICAL CHARACTERISTICS FOR MV CABLES SHEATHING
Sheathing materials propertiesProperties Units Materials Test Method
TPO TPR
Tensile strength N/mm² >12.5 >10 EN 60811-1-1
Elongation at break % 300 125 EN 60811-1-1
Tear resistance N/mm >20 >8 ISO 34.1
Abrasion resistance on cable
- Pass Not pass HD-605.2.4.22
Oxygen index - >27 >32 ISO 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 50267-2-3
EN 50267-2-1
9ROVIRA-SP-ALPHA1-BLOCK2
Barcelona 12-15 May 2003
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