Cable Insulation

Last updated on 2023-03-31 2 mins. to read

Cable insulation is used to provide electrical separation between conductors of a cable. During the historical development of cables, numerous types of insulation have been employed. During recent years, there has been some consolidation in the types of insulation used.

HDPE Cable Insulation Resin

Thermoplastic and Thermosetting

While there are a vast array of cable insulation materials, these are often divided into two general  types;  Thermoplastic or  Thermosetting.   For example the current capacity determination of a cable in accordance with  the UK Wiring Regulations is categorized into thermoplastic and thermosetting cables.

Thermoplastic materials are composed of chains of  molecules (polyethylene for example).  When heat is applied the energy will allow the bonds to separate and the material can flow (melt) and be reformed.

Thermosetting materials are formed when materials such as polyethylene undergo specific heating or chemical processes. During this process the individual chains become cross linked by smaller molecules making a rigid structure.    Thermosetting materials cannot reheated, melted and remolded.

While thermoplastic materials have the advantage of being able to be reformed, thermosetting materials are generally more heat resistance and have greater strength.

The operating temperature of any cable is an important parameter in determining the maximum allowable current.   While the actual temperature varies depending on the material used, the UK Wiring Regulations limits the choice in calculating the current rating to two temperatures only:

  • Thermoplastic 70 °0C
  • Thermosetting 90 °C

Note: more specific calculations based on actual material properties are allowed.  However, for ease of use most practical application will use 70 °C or 90 °C and the methods outlined in the regulations.

Cross-linking of insulation

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Elastomere Materials

Last updated on 2023-03-31 9 mins. to read
 

G

2G

3G

4G

5G

6G

NR 
SBR

SiR

EPR

EVA

CR

CSM

Natural Rubber 
Styrol- 
Butadiene Rubber 
Compounds

Silicone Rubber

Ethylen- 
Propylene 
Rubber 
Compounds

Ethylene- 
Vinylacetate
Copolymere
Compounds

Poly- 
Chloroprene
Compounds

Chloro- 
Sulfonated 
Polyethylene
Compounds

Density g/cm3

1.5-1.7

1.2-1.3

1.3-1.55

1.3-1.5

1.4-1.65

1.3-1.6

Breakdown Voltage KV/mm (20oC)

20

20

20

30

20

25

Specific Volume Resistivity Ω cm (20oC)

1012-1015

1015

1014

1012

1010

1012

Dielectric Constant 50 Hz (20oC)

3-5

3-4

3-3.8

5-6.5

6-8.5

6-9

Dielectric Loss Factor (tan δ)

1.9 x 10-2

6x 10-3

3.4 x 10-3

2 x 10-2

5 x 10-2

2.8 x 10-2

Working 
Temperature

Permanent oC

-65 +60

-60 +180

-30 +90

-30 +125

-40 +100

-30 +80

Short Time oC

+120

+260

+160

+200

+140

+140

Melt  Temperature +oC

-

-

-

-

-

+160

Flame Resistance

Flammable

High Flash Point

Flammable

Flammable

Self 
Extinguishing

Self 
Extinguishing

Oxygen Index LOI (% O2)

≤22

25-35

≤22

≤22

30-35

30-35

Heating Value H0 MJ.kg-1

21-25

17-19

21-25

19-23

14-19

19-23

Thermal Conductivity W.K-1.m-1

-

0.22

-

-

-

-

Corrosive Gases In Case Of Fire

No

No

No

No

Hydrogen Chloride

Hydrogen Chloride

Radiation Resistance max Mrad

100

50

200

100

50

50

Tensile Strength N/mm2

5-10

5-10

5-10

8-12

10-20

10-20

Elongation At Break %

300-600

300-600

200-400

250-350

400-700

350-600

Shore Hardness

60-70 (A)

40-80 (A)

65-85 (A)

70-80 (A)

55-70 (A)

60-70 (A)

Abrasion Resistance

Moderate

Moderate

Moderate

Moderate

Medium

Medium

Water Absorption %

1.0

1.0

1.0

1.0

1.0

1.5

Halogen Free

No

Yes

Yes

Yes

No

No

Weather Resistance

Moderate

Good

Very Good

Good

Very Good

Very Good

Cold Resistance

Very Good

Very Good

Good

Good

Moderate

Moderate

 

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Halogen Free Compounds

Last updated on 2023-03-31 4 mins. to read
 

H

HX

Not Cross Linked

Cross Linked

Halogen Free 
Polymer Compounds

Halogen Free 
Polymer Compounds

Density g/cm3

1.4-1.6

1.4-1.6

Breakdown Voltage KV/mm (20oC)

25

25

Specific Volume Resistivity Ω cm (20oC)

1012-1014

1013-1014

Dielectric Constant 50 Hz (20oC)

3.4-5

3.4-5

Dielectric Loss Factor (tan δ)

~10-3

10-2-10-3

Working 
Temperature

Permanent oC

-30 +70

-30 +90

Short Time oC

+100

+150

Melt  Temperature +oC

>130

-

Flame Resistance

Self Extinguishing

Self Extinguishing

Oxygen Index LOI (% O2)

≤40

≤40

Heating Value H0 MJ.kg-1

17-22

16-25

Thermal Conductivity W.K-1.m-1

0.17

0.20

Corrosive Gases In Case Of Fire

No

No

Radiation Resistance max Mrad

100

200

Tensile Strength N/mm2

8-13

8-13

Elongation At Break %

150-250

150-250

Shore Hardness

65-95 (A)

65-95 (A)

Abrasion Resistance

Medium

Medium

Water Absorption %

0.2-1.5

0.2-1.5

Halogen Free

Yes

Yes

Weather Resistance

Medium in Black: 
Good

Medium in Black: 
Good

Cold Resistance

Average

Average

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High Temperature Materials

Last updated on 2023-03-31 7 mins. to read
 

10Y

7Y

6Y

5YX

5Y

PVDF

ETFE

FEP

PFA

PTFE

Polyvinylidene
Fluoride 
Kynar/Dyflor

Ethylene- 
Tetrafluorethylene

 

Fluorine Ethylene 
Propylene

Perfluoral- 
Koxypolymeric

Poly- 
Tetrafluorethylene

Density g/cm3

1.7-1.9

1.6-1.8

2.0-2.3

2.0-2.3

2.0-2.3

Breakdown Voltage KV/mm (20oC)

25

36

25

25

20

Specific Volume Resistivity Ω cm (20oC)

1014

1016

1018

1018

1018

Dielectric Constant 50 Hz (20oC)

9-7

2.6

2.1

2.1

2.1

Dielectric Loss Factor (tan δ)

1.4 x 10-2

8 x 10-4

3 x 10-4

3 x 10-4

3 x 10-4

Working 
Temperature

Permanent oC

-40 +135

-100 +150

-100 +205

-190 +260

-190 +260

Short Time oC

+160

+180

+230

+280

+300

Melt  Temperature +oC

>170

>265

>225

>290

>325

Flame Resistance

Self 
Extinguishing

Self 
Extinguishing

Self 
Extinguishing

Self 
Extinguishing

Self 
Extinguishing

Oxygen Index LOI (% O2)

40-45

30-35

>95

>95

>95

Heating Value H0 MJ.kg-1

15

14

5

5

5

Thermal Conductivity W.K-1.m-1

0.17

0.24

0.26

0.21

0.26

Corrosive Gases In Case Of Fire

Hydrofluoric

Yes

Yes

Yes

Yes

Radiation Resistance max Mrad

10

10

1

0.1

0.1

Tensile Strength N/mm2

50-80

40-50

15-25

25-30

80

Elongation At Break %

150

150

250

250

50

Shore Hardness

75-80 (D)

70-75 (D)

55-60 (D)

55-60 (D)

55-60 (D)

Abrasion Resistance

Very Good

Very Good

Very Good

Very Good

Very Good

Water Absorption %

0.01

0.02

0.01

0.01

0.01

Halogen Free

No

No

No

No

No

Weather Resistance

Very Good

Very Good

Very Good

Very Good

Very Good

Cold Resistance

Very Good

Very Good

Very Good

Very Good

Very Good

 

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Harsha Durugoji Jul 14, 2022 7:12 AM
What does those 6 7Y means on the top row?
Reply
Steven McFadyen Jul 14, 2022 11:00 AM
It is the VDE code.
Reply

Other Insulation

Last updated on 2023-03-31 8 mins. to read
 

3Y

4Y

9Y

11Y

TPE-E (12Y)

TPE-O

PS

PA

PP

PUR

 

 

Polystrole

Polyamide

Poly-propylene

Poly-urethane

PolYester 
Elastomer

Polyolefine
Elastomer

Density g/cm3

1.05

1.02-1.1

0.91

1.15-1.2

1.2-1.4

0.89-1.0

Breakdown Voltage KV/mm (20oC)

30

30

75

20

40

30

Specific Volume Resistivity Ω cm (20oC)

1016

1015

1016

1010-1012

>1010

>1014

Dielectric Constant 50 Hz (20oC)

2.5

4

2.3-2.4

4-7

3.7-5.1

2.7-3.6

Dielectric Loss Factor (tan δ)

1 x 10-4

2 x 10-2 to 1 x 10-3

4 x 10-4

2.3 x 10-2

1.8 x 10-2

1.8 x 10-2

Working 
Temperature

Permanent oC

-50 +80

-60 +05

-10 +100

-55 +80

-50 +100

-50 +100

Short Time oC

+100

+125

+140

+100

+140

+130

Melt  Temperature +oC

>120

210

160

150

190

150

Flame Resistance

Flammable

Flammable

Flammable

Flammable

Flammable

Flammable

Oxygen Index LOI (% O2)

≤22

≤22

≤22

≤22

≤29

≤25

Heating Value H0 MJ.kg-1

40-43

27-31

42-44

20-26

20-25

23-28

Thermal Conductivity W.K-1.m-1

0.25

0.23

0.19

0.25

0.5

1.5

Corrosive Gases In Case Of Fire

No

No

No

No

No

No

Radiation Resistance max Mrad

80

10

10

100

10

10

Tensile Strength N/mm2

55-65

50-60

20-35

30-45

30

20

Elongation At Break %

300-400

50-170

300

500-700

>300

>300

Shore Hardness

35-50 (D)

-

55-60 (D)

70-100 (A)

85 (A), 70 (D)

55 (A), 70 (D)

Abrasion Resistance

Good

Very Good

Medium

Very Good

Good

Good

Water Absorption %

0.4

1.0-1.5

0.1

1.5

1.5

1.5

Halogen Free

Yes

Yes

Yes

Yes

Yes

Yes

Weather Resistance

Medium - Good

Good

Moderate

Very Good

Very Good

Very Good

Cold Resistance

Moderate - Good

Good

Good

Very Good

Very Good

Very Good

 

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PE Insulation

Last updated on 2023-03-31 6 mins. to read
 

2Y

2Y

2X

O2Y

LDPE

HDPE

VPE

 

Low density 
Polyethylene

High density 
Polyethylene

Cross Linked 
Polyethylene

Foamed 
Polyethylene

Density g/cm3

0.92-0.94

0.94-0.98

0.92

≈0.65

Breakdown Voltage KV/mm (20oC)

70

85

50

30

Specific Volume Resistivity Ω cm (20oC)

1017

1017

1012-1016

1017

Dielectric Constant 50 Hz (20oC)

2.3

2.3

4-6

≈1.55

Dielectric Loss Factor (tan δ)

2 x 10-4

3 x 10-4

2x 10-3

5 x 10-4

Working 
Temperature

Permanent oC

-50 +70

-50 +00

-35 +90

-40 +70

Short Time oC

+100

+120

+100

+100

Melt  Temperature +oC

105-110

130

-

105

Flame Resistance

Flammable

Flammable

Flammable

Flammable

Oxygen Index LOI (% O2)

≤22

≤22

≤22

18-30

Heating Value H0 MJ.kg-1

42-44

42-44

42-44

42-44

Thermal Conductivity W.K-1.m-1

0.3

0.4

0.3

0.25

Corrosive Gases In Case Of Fire

No

No

No

No

Radiation Resistance max Mrad

100

100

100

100

Tensile Strength N/mm2

10-20

20-30

12.5-20

8-12

Elongation At Break %

400-600

500-1000

300-400

350-450

Shore Hardness

43-50 (D)

60-63 (D)

40-45 (D)

-

Abrasion Resistance

Medium

Good

Medium

-

Water Absorption %

0.1

0.1

0.1

-

Halogen Free

Yes

Yes

Yes

Conditional

Weather Resistance

Medium 
(Black: Good)

Medium 
(Black: Good)

Good

-

Cold Resistance

Good

Good

Good

Good

 

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PVC Insulation

Last updated on 2023-03-31 6 mins. to read
 

Y

Yw

Yw

Yk

PVC

PVC

PVC

PVC

Polyvinylchloride 
Compounds

Heat-resistant 
90oC

Heat-resistant 
105oC

Cold 
Resistant

Density g/cm3

1.35 - 1.5

1.3-1.5

1.3-1.5

1.2-1.

Breakdown Voltage KV/mm (20oC)

25

25

25

25

Specific Volume Resistivity Ω cm (20oC)

1013-1015

1012-1015

1012-1015

1012-1015

Dielectric Constant 50 Hz (20oC)

3.6-6

4-6.5

4.5-6.5

4.5-6.5

Dielectric Loss Factor (tan δ)

4 x 10-2 to 1 x 10-1

4 x 10-2 to 1 x 10-1

4 x 10-2 to 1 x 10-1

4 x 10-2 to 1 x 10-1

Working 
Temperature

Permanent oC

-30 +70

-20 +90

-20 +105

-40 +70

Short Time oC

+100

+120

+120

+100

Melt  Temperature +oC

>140

>140

>140

>140

Flame Resistance

Self Extinguishing

Self Extinguishing

Self Extinguishing

Self Extinguishing

Oxygen Index LOI (% O2)

23-42

23-42

24-42

24-42

Heating Value H0 MJ.kg-1

17-25

16-22

16-20

17-24

Thermal Conductivity W.K-1.m-1

0.17

0.17

0.17

0.17

Corrosive Gases In Case Of Fire

Hydrogen Chloride

Hydrogen Chloride

Hydrogen Chloride

Hydrogen Chloride

Radiation Resistance max Mrad

80

80

80

80

Tensile Strength N/mm2

10-25

10-25

10-25

10-25

Elongation At Break %

130-350

130-350

130-350

130-350

Shore Hardness

70-95 (A)

70-95 (A)

70-95 (A)

70-95 (A)

Abrasion Resistance

Medium

Medium

Medium

Medium

Water Absorption %

0.4

0.4

0.4

0.4

Halogen Free

No

No

No

No

Weather Resistance

Medium 
(Black: Good)

Medium 
(Black: Good)

Medium 
(Black: Good)

Medium 
(Black: Good)

Cold Resistance

Moderate - Good

Moderate - Good

Moderate - Good

Very  Good

 

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