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